Q: Does the order of the tape & pipe sealant matter?

Starting with this:
http://www2.picturepush.com/photo/a/...g/12901000.jpg

Just wondering, if, for critical 2" PVC applications such as
pool equipment, when using *both* pipe sealant & teflon tape:
http://www5.picturepush.com/photo/a/...g/12900978.jpg

Does it matter if we put the teflon tape first:
http://www3.picturepush.com/photo/a/...g/12901031.jpg

And then the pipe sealant?
http://www1.picturepush.com/photo/a/...g/12901034.jpg

Before screwing the fitting into the housing:
http://www5.picturepush.com/photo/a/...g/12901038.jpg

Just curious:
Q: Does the order of the tape & pipe sealant matter?

Danny D wrote:
Q: Does the order of the tape & pipe sealant matter?

Starting with this:
http://www2.picturepush.com/photo/a/...g/12901000.jpg

Just wondering, if, for critical 2" PVC applications such as
pool equipment, when using *both* pipe sealant & teflon tape:
http://www5.picturepush.com/photo/a/...g/12900978.jpg

Does it matter if we put the teflon tape first:
http://www3.picturepush.com/photo/a/...g/12901031.jpg

And then the pipe sealant?
http://www1.picturepush.com/photo/a/...g/12901034.jpg

Before screwing the fitting into the housing:
http://www5.picturepush.com/photo/a/...g/12901038.jpg

Just curious:
Q: Does the order of the tape & pipe sealant matter?

I'd use one or the other, not both.

Teflon is primarily a lubricant and is most effective on NPT fittings. NPT
fittings change their pitch so that the connected pieces deform the pipe
threads more and more making the seal.

Other types of threading do not change the thread pitch (if there is any
involved in the seal), so any imperfections are better dealth with by a pipe
sealant.

On May 11, 8:14*am, "HeyBub" wrote:
Danny D wrote:
Q: Does the order of the tape & pipe sealant matter?

Starting with this:
http://www2.picturepush.com/photo/a/...g/12901000.jpg

Just wondering, if, for critical 2" PVC applications such as
pool equipment, when using *both* pipe sealant & teflon tape:
http://www5.picturepush.com/photo/a/...g/12900978.jpg

Does it matter if we put the teflon tape first:
http://www3.picturepush.com/photo/a/...g/12901031.jpg

And then the pipe sealant?
http://www1.picturepush.com/photo/a/...g/12901034.jpg

Before screwing the fitting into the housing:
http://www5.picturepush.com/photo/a/...g/12901038.jpg

Just curious:
Q: Does the order of the tape & pipe sealant matter?

I'd use one or the other, not both.

Teflon is primarily a lubricant and is most effective on NPT fittings. NPT
fittings change their pitch so that the connected pieces deform the pipe
threads more and more making the seal.

Other types of threading do not change the thread pitch (if there is any
involved in the seal), so any imperfections are better dealth with by a pipe
sealant.

a plumber friend uses tape and then dope, on every joint to avoid leaks

On Sat, 11 May 2013 05:26:00 -0700 (PDT), bob haller
wrote:




a plumber friend uses tape and then dope, on every joint to avoid leaks

Does he wear a belt and suspenders too?

I know people that use both, but I know people that use one or the
other and don't have leaks. One advantage of tape is when you take it
apart five or ten years later, it is probably going to be easier.
Joint compound can get hard.

Actually, I do both. Tape, dope, belt,
suspenders. For real.
..
Christopher A. Young
Learn more about Jesus
www.lds.org
..
..
"Ed Pawlowski" wrote in message ...

a plumber friend uses tape and then dope, on every joint to avoid leaks

Does he wear a belt and suspenders too?

I know people that use both, but I know people that use one or the
other and don't have leaks. One advantage of tape is when you take it
apart five or ten years later, it is probably going to be easier.
Joint compound can get hard.

On May 11, 7:54 am, "Stormin Mormon"
wrote:
Actually, I do both. Tape, dope, belt,
suspenders. For real.
.
Christopher A. Young


When I put pipe dope on my suspenders, they never
leak.....

On May 11, 8:46*am, Ed Pawlowski wrote:
On Sat, 11 May 2013 05:26:00 -0700 (PDT), bob haller
wrote:



a plumber friend uses tape and then dope, on every joint to avoid leaks

Does he wear a belt and suspenders too?

I know people that use both, but I know people that use one or the
other and don't have leaks. *One advantage of tape is when you take it
apart five or ten years later, it is probably going to be easier.
Joint compound can get hard.

I use one or the other too, never both. Usually I use tape. And I
rarely have a problem.

On Sat, 11 May 2013 08:46:16 -0400, Ed Pawlowski wrote:

Joint compound can get hard.

I can get hard too!!!! (even without Viagra)....

On Sat, 11 May 2013 05:26:00 -0700 (PDT), bob haller
wrote:

On May 11, 8:14*am, "HeyBub" wrote:
Danny D wrote:
Q: Does the order of the tape & pipe sealant matter?

Starting with this:
http://www2.picturepush.com/photo/a/...g/12901000.jpg

Just wondering, if, for critical 2" PVC applications such as
pool equipment, when using *both* pipe sealant & teflon tape:
http://www5.picturepush.com/photo/a/...g/12900978.jpg

Does it matter if we put the teflon tape first:
http://www3.picturepush.com/photo/a/...g/12901031.jpg

And then the pipe sealant?
http://www1.picturepush.com/photo/a/...g/12901034.jpg

Before screwing the fitting into the housing:
http://www5.picturepush.com/photo/a/...g/12901038.jpg

Just curious:
Q: Does the order of the tape & pipe sealant matter?

I'd use one or the other, not both.

Teflon is primarily a lubricant and is most effective on NPT fittings. NPT
fittings change their pitch so that the connected pieces deform the pipe
threads more and more making the seal.

Other types of threading do not change the thread pitch (if there is any
involved in the seal), so any imperfections are better dealth with by a pipe
sealant.

a plumber friend uses tape and then dope, on every joint to avoid leaks

Pipe or dope - not both. Read the instructions on either one.

On May 11, 5:14*am, "HeyBub" wrote:
Danny D wrote:
Q: Does the order of the tape & pipe sealant matter?

Starting with this:
http://www2.picturepush.com/photo/a/...g/12901000.jpg

Just wondering, if, for critical 2" PVC applications such as
pool equipment, when using *both* pipe sealant & teflon tape:
http://www5.picturepush.com/photo/a/...g/12900978.jpg

Does it matter if we put the teflon tape first:
http://www3.picturepush.com/photo/a/...g/12901031.jpg

And then the pipe sealant?
http://www1.picturepush.com/photo/a/...g/12901034.jpg

Before screwing the fitting into the housing:
http://www5.picturepush.com/photo/a/...g/12901038.jpg

Just curious:
Q: Does the order of the tape & pipe sealant matter?

I'd use one or the other, not both.

Teflon is primarily a lubricant and is most effective on NPT fittings. NPT
fittings change their pitch so that the connected pieces deform the pipe
threads more and more making the seal.

Other types of threading do not change the thread pitch (if there is any
involved in the seal), so any imperfections are better dealth with by a pipe
sealant.

A lot incorrect information.....

1) Teflon is primarily a lubricant it is material to seal the
naturally occurring / designed in clearance between internal &
external pipe threads.


2) NPT fittings change their pitch so that the connected pieces deform
the pipe threads more and more making the seal. incorrect for
ubiquitous / normally used / everyday NPT threads.

NPT pipe threads do NOT have interference thread forms, they do not
change pitch.
If they deformed, how could new fittings be used on old pipe?

"Dry fit" pipe threads do exist & do seal based on interference but
they are seldom encountered in daily life.
I used them ~30 year on military hydraulic systems where dope & tape
were prohibited. Dry seal threads are a bitch to use, they sucked...
a major PITA. Be thankful that everyday threads are not as you
describe.

Take a look at the wikipedia article on pipe threads.

cheers
Bob

DD_BobK wrote:

I'd use one or the other, not both.

Teflon is primarily a lubricant and is most effective on NPT
fittings. NPT fittings change their pitch so that the connected
pieces deform the pipe threads more and more making the seal.

Other types of threading do not change the thread pitch (if there is
any involved in the seal), so any imperfections are better dealth
with by a pipe sealant.

A lot incorrect information.....

1) Teflon is primarily a lubricant it is material to seal the
naturally occurring / designed in clearance between internal &
external pipe threads.


2) NPT fittings change their pitch so that the connected pieces deform
the pipe threads more and more making the seal. incorrect for
ubiquitous / normally used / everyday NPT threads.

NPT pipe threads do NOT have interference thread forms, they do not
change pitch.
If they deformed, how could new fittings be used on old pipe?

"Dry fit" pipe threads do exist & do seal based on interference but
they are seldom encountered in daily life.
I used them ~30 year on military hydraulic systems where dope & tape
were prohibited. Dry seal threads are a bitch to use, they sucked...
a major PITA. Be thankful that everyday threads are not as you
describe.

Take a look at the wikipedia article on pipe threads.


Likewise, look at the article on thread sealing tape:

"One of the defining characteristics of PTFE (Teflon) is how good it is at
defeating friction. The use of PTFE tape in tapered pipe threads performs a
lubricating function, which more easily allows the threads to be screwed
together, to the point of deformation, which is what creates the seal."

On Sun, 12 May 2013 07:00:15 -0500, "HeyBub"
wrote:

DD_BobK wrote:

I'd use one or the other, not both.

Teflon is primarily a lubricant and is most effective on NPT
fittings. NPT fittings change their pitch so that the connected
pieces deform the pipe threads more and more making the seal.

Other types of threading do not change the thread pitch (if there is
any involved in the seal), so any imperfections are better dealth
with by a pipe sealant.

A lot incorrect information.....

1) Teflon is primarily a lubricant it is material to seal the
naturally occurring / designed in clearance between internal &
external pipe threads.


2) NPT fittings change their pitch so that the connected pieces deform
the pipe threads more and more making the seal. incorrect for
ubiquitous / normally used / everyday NPT threads.

NPT pipe threads do NOT have interference thread forms, they do not
change pitch.
If they deformed, how could new fittings be used on old pipe?

"Dry fit" pipe threads do exist & do seal based on interference but
they are seldom encountered in daily life.
I used them ~30 year on military hydraulic systems where dope & tape
were prohibited. Dry seal threads are a bitch to use, they sucked...
a major PITA. Be thankful that everyday threads are not as you
describe.

Take a look at the wikipedia article on pipe threads.


Likewise, look at the article on thread sealing tape:

"One of the defining characteristics of PTFE (Teflon) is how good it is at
defeating friction. The use of PTFE tape in tapered pipe threads performs a
lubricating function, which more easily allows the threads to be screwed
together, to the point of deformation, which is what creates the seal."

Just because it is a lubricand doesn't mean it is not also a sealer -
and vise versa. If all you need is a lubricant, just oil the threads
and see how well it seals - or grease the threads. It is a combination
product.

On Sun, 12 May 2013 16:05:09 -0400, clare wrote:

Just because it is a lubricand doesn't mean it is not also
a sealer - and vise versa.

I ended up using the 2-in-one lubricant + sealer, after
taking pains to remove all vestiges of the Teflon tape.

BTW, do we lubricate the unions?
http://www3.picturepush.com/photo/a/...g/12918676.jpg

I think they go on dry ... but I also thought Teflon tape was
to be used on the threaded fittings (and that was wrong).

On May 12, 5:00*am, "HeyBub" wrote:
DD_BobK wrote:

I'd use one or the other, not both.

Teflon is primarily a lubricant and is most effective on NPT
fittings. NPT fittings change their pitch so that the connected
pieces deform the pipe threads more and more making the seal.

Other types of threading do not change the thread pitch (if there is
any involved in the seal), so any imperfections are better dealth
with by a pipe sealant.

A lot incorrect information.....

1) Teflon is primarily a lubricant * it is material to seal the
naturally occurring / designed in clearance between internal &
external pipe threads.

2) NPT fittings change their pitch so that the connected pieces deform
the pipe *threads more and more making the seal. incorrect for
ubiquitous / normally used / everyday *NPT threads. *

NPT pipe threads do NOT have interference thread forms, they do not
change pitch.
If they deformed, how could new fittings be used on old pipe?

"Dry fit" pipe threads do exist & do seal based on interference but
they are seldom encountered in daily life.
I used them ~30 year on military hydraulic systems where dope & tape
were prohibited. *Dry seal threads are a bitch to use, they sucked...
a major PITA. *Be thankful that everyday threads are not as you
describe.

Take a look at the wikipedia article on pipe threads.

Likewise, look at the article on thread sealing tape:

"One of the defining characteristics of PTFE (Teflon) is how good it is at
defeating friction. The use of PTFE tape in tapered pipe threads performs a
lubricating function, which more easily allows the threads to be screwed
together, to the point of deformation, which is what creates the seal."

HB-

Please provide sight / link for following.....

""One of the defining characteristics of PTFE (Teflon) is how good it
is at
defeating friction. The use of PTFE tape in tapered pipe threads
performs a
lubricating function, which more easily allows the threads to be
screwed
together, to the point of deformation, which is what creates the
seal."


to the point of deformation

I assume you mean deformation of the threads? & not the tape?

Internal & external threads of NPT threads type do not interfere with
each other.
Take a look in Machinery's Handbook to get an idea of the design of
NPT threads.
There is a designed in & manufactured in clearance between the crests
& the valleys..
thus creating a spiral leak path that needs a sealant not a lube.

cheers
Bob

On May 13, 4:28*am, DD_BobK wrote:
On May 12, 5:00*am, "HeyBub" wrote:









DD_BobK wrote:

I'd use one or the other, not both.

Teflon is primarily a lubricant and is most effective on NPT
fittings. NPT fittings change their pitch so that the connected
pieces deform the pipe threads more and more making the seal.

Other types of threading do not change the thread pitch (if there is
any involved in the seal), so any imperfections are better dealth
with by a pipe sealant.

A lot incorrect information.....

1) Teflon is primarily a lubricant * it is material to seal the
naturally occurring / designed in clearance between internal &
external pipe threads.

2) NPT fittings change their pitch so that the connected pieces deform
the pipe *threads more and more making the seal. incorrect for
ubiquitous / normally used / everyday *NPT threads. *

NPT pipe threads do NOT have interference thread forms, they do not
change pitch.
If they deformed, how could new fittings be used on old pipe?

"Dry fit" pipe threads do exist & do seal based on interference but
they are seldom encountered in daily life.
I used them ~30 year on military hydraulic systems where dope & tape
were prohibited. *Dry seal threads are a bitch to use, they sucked....
a major PITA. *Be thankful that everyday threads are not as you
describe.

Take a look at the wikipedia article on pipe threads.

Likewise, look at the article on thread sealing tape:

"One of the defining characteristics of PTFE (Teflon) is how good it is at
defeating friction. The use of PTFE tape in tapered pipe threads performs a
lubricating function, which more easily allows the threads to be screwed
together, to the point of deformation, which is what creates the seal."

HB-

Please provide sight / link for *following.....

""One of the defining characteristics of PTFE (Teflon) is how good it
is at
defeating friction. The use of PTFE tape in tapered pipe threads
performs a
lubricating function, which more easily allows the threads to be
screwed
together, to the point of deformation, which is what creates the
seal."

to the point of deformation

I assume you mean deformation of the threads? *& not the tape?

Internal & external threads of NPT threads type do not interfere with
each other.
Take a look in Machinery's Handbook to get an idea of the design of
NPT threads.
There is a designed in & manufactured in clearance between the crests
& the valleys..
thus creating a spiral leak path that needs a sealant not a lube.

cheers
Bob

I should add to be clear....

NPT threads need a sealant to seal the spiral leak path.
NPT threads do not seal by thread deformation.

Hint: To do a practical proof of want I knew to be the design intent
of NPT threads,
I did the lube alone assembly of NPT pipe & fittings.... they leak no
matter how tight.
I used oil so that no "sealant" was present.

cheers
Bob

On May 12, 5:00*am, "HeyBub" wrote:
DD_BobK wrote:

I'd use one or the other, not both.

Teflon is primarily a lubricant and is most effective on NPT
fittings. NPT fittings change their pitch so that the connected
pieces deform the pipe threads more and more making the seal.

Other types of threading do not change the thread pitch (if there is
any involved in the seal), so any imperfections are better dealth
with by a pipe sealant.

A lot incorrect information.....

1) Teflon is primarily a lubricant * it is material to seal the
naturally occurring / designed in clearance between internal &
external pipe threads.

2) NPT fittings change their pitch so that the connected pieces deform
the pipe *threads more and more making the seal. incorrect for
ubiquitous / normally used / everyday *NPT threads. *

NPT pipe threads do NOT have interference thread forms, they do not
change pitch.
If they deformed, how could new fittings be used on old pipe?

"Dry fit" pipe threads do exist & do seal based on interference but
they are seldom encountered in daily life.
I used them ~30 year on military hydraulic systems where dope & tape
were prohibited. *Dry seal threads are a bitch to use, they sucked...
a major PITA. *Be thankful that everyday threads are not as you
describe.

Take a look at the wikipedia article on pipe threads.

Likewise, look at the article on thread sealing tape:

"One of the defining characteristics of PTFE (Teflon) is how good it is at
defeating friction. The use of PTFE tape in tapered pipe threads performs a
lubricating function, which more easily allows the threads to be screwed
together, to the point of deformation, which is what creates the seal."

to the point of deformation, which is what creates the seal."

deformation of the threads or the tape?

The crests & valleys of internal & external NPT pipe threads NEVER
touch.
Look at the thread form description in Machinery's Handbook.

The spiral leak path ALWAYS exists, this spiral MUST be seal with a
sealing compound.
You can tighten lubricated NPT pipe & fitting joints 'til you run out
of torque ..the joint will leak unless sealant is used.

On Sat, 11 May 2013 04:30:52 +0000 (UTC), Danny D
wrote:

Q: Does the order of the tape & pipe sealant matter?

Starting with this:
http://www2.picturepush.com/photo/a/...g/12901000.jpg

Just wondering, if, for critical 2" PVC applications such as
pool equipment, when using *both* pipe sealant & teflon tape:
http://www5.picturepush.com/photo/a/...g/12900978.jpg

Does it matter if we put the teflon tape first:
http://www3.picturepush.com/photo/a/...g/12901031.jpg

And then the pipe sealant?
http://www1.picturepush.com/photo/a/...g/12901034.jpg

Before screwing the fitting into the housing:
http://www5.picturepush.com/photo/a/...g/12901038.jpg

Just curious:
Q: Does the order of the tape & pipe sealant matter?

According to this, tape is a no-no
http://www.lascofittings.com/support...dedPlastic.asp.

On May 11, 9:22*am, Vic Smith wrote:
On Sat, 11 May 2013 04:30:52 +0000 (UTC), Danny D
wrote:





Q: Does the order of the tape & pipe sealant matter?

Starting with this:
http://www2.picturepush.com/photo/a/...g/12901000.jpg

Just wondering, if, for critical 2" PVC applications such as
pool equipment, when using *both* pipe sealant & teflon tape:
http://www5.picturepush.com/photo/a/...g/12900978.jpg

Does it matter if we put the teflon tape first:
http://www3.picturepush.com/photo/a/...g/12901031.jpg

And then the pipe sealant?
http://www1.picturepush.com/photo/a/...g/12901034.jpg

Before screwing the fitting into the housing:
http://www5.picturepush.com/photo/a/...g/12901038.jpg

Just curious:
Q: Does the order of the tape & pipe sealant matter?

According to this, tape is a no-nohttp://www.lascofittings.com/supportcenter/TheDosandDontsThreadedPlas....- Hide quoted text -

- Show quoted text -

That's a good find. What they are saying makes sense and they
should know. I've used tape for years and rarely had a problem.
But part of it is probably because I know how much to tighten them
and don't over tighten a fitting to crack it. For the future, I'll
use
joint compound.

Also, the part about Sched 80 vs 40 was interesting. Particularly
the part about how any threaded PVC joint reduced the overall
pressure rating by 50% compared to all glued connections.

On Sat, 11 May 2013 06:50:06 -0700, wrote:

Also, the part about Sched 80 vs 40 was interesting. Particularly
the part about how any threaded PVC joint reduced the overall
pressure rating by 50% compared to all glued connections.

+1

On May 11, 9:51*am, Danny D wrote:
On Sat, 11 May 2013 06:50:06 -0700, wrote:
Also, the part about Sched 80 vs 40 was interesting. *Particularly
the part about how any threaded PVC joint reduced the overall
pressure rating by 50% compared to all glued connections.

+1

The whole treatise was very informative, I'm sending the web address
to several DIY'ers I know.

On 5/11/2013 10:43 AM, wrote:
On May 11, 9:51 am, Danny wrote:
On Sat, 11 May 2013 06:50:06 -0700, wrote:
Also, the part about Sched 80 vs 40 was interesting. Particularly
the part about how any threaded PVC joint reduced the overall
pressure rating by 50% compared to all glued connections.

+1

The whole treatise was very informative, I'm sending the web address
to several DIY'ers I know.

While basically true there are some fallacies there, particularly wrt to
the Sch 80 vs Sch 40 discussion on stresses.

The stress on a Sch 80 fitting is _not_ the same as that for a Sch 40
fitting--the extra thickness _DOES_ make a difference because the
remaining cross-sectional area remaining after the threads are cut is
thicker and that increases the denominator (the per sq in portion of the
stress which has units of psi).

I've not gone and looked up actual dimensions, but the percentage
increase in remaining thickness will be quite significant.

--

On Sat, 11 May 2013 08:22:29 -0500, Vic Smith wrote:

According to this, tape is a no-no
http://www.lascofittings.com/support...dedPlastic.asp

Interesting conclusions.

I noticed a LOT of my threaded fittings are gray (schedule 80?)
and most of the glued "end" fittings (near the pumps & valves)
are gray thicker stuff (schedule 200?).

Asking at a pool store, they said they use gray fittings
near the pump "because they handle heat better".

Yet, that article says both teflon tape and schedule 80 fittings
are a no no.

Interesting though the schedule 40 PVC tensile strength of 7K psi
and the PVC thread "resistance" of 400K PSI.

For 2" pipe, apparently each turn past finger tight adds 0.00239
inches per inch, times that 400K psi, nets almost a thousand psi
per turn (956 psi per turn).

The chart gives us only about 4,000 PSI as the maximum allowable
(3912 psi); so it seems that 4 turns past finger tight is the
maximum one can go with schedule 40 PVC.

In summary, that article recommends, for my 2" PVC plumbing:
1. Pipe dope (not teflon tape).
2. Two turns after finger tight (never more than 4).
3. Only schedule 40 plastic (no schedule 80).

It was also interesting that a single threaded fitting reduces
the strength of the system by half the original strength!

On May 11, 7:50*am, Danny D wrote:
On Sat, 11 May 2013 08:22:29 -0500, Vic Smith wrote:
According to this, tape is a no-no
http://www.lascofittings.com/support...tsThreadedPlas...

Interesting conclusions.

I noticed a LOT of my threaded fittings are gray (schedule 80?)
and most of the glued "end" fittings (near the pumps & valves)
are gray thicker stuff (schedule 200?).

Asking at a pool store, they said they use gray fittings
near the pump "because they handle heat better".

Yet, that article says both teflon tape and schedule 80 fittings
are a no no.

Interesting though the schedule 40 PVC tensile strength of 7K psi
and the PVC thread "resistance" of 400K PSI.

For 2" pipe, apparently each turn past finger tight adds 0.00239
inches per inch, times that 400K psi, nets almost a thousand psi
per turn (956 psi per turn).

The chart gives us only about 4,000 PSI as the maximum allowable
(3912 psi); so it seems that 4 turns past finger tight is the
maximum one can go with schedule 40 PVC.

In summary, that article recommends, for my 2" PVC plumbing:
1. Pipe dope (not teflon tape).
2. Two turns after finger tight (never more than 4).
3. Only schedule 40 plastic (no schedule 80).

It was also interesting that a single threaded fitting reduces
the strength of the system by half the original strength!

I saw no place that says "no chedule 80". It says DO NOT MIX 40 and
80 schedule.

Harry K

On May 11, 10:22*am, Harry K wrote:
On May 11, 7:50*am, Danny D wrote:









On Sat, 11 May 2013 08:22:29 -0500, Vic Smith wrote:
According to this, tape is a no-no
http://www.lascofittings.com/support...tsThreadedPlas....

Interesting conclusions.

I noticed a LOT of my threaded fittings are gray (schedule 80?)
and most of the glued "end" fittings (near the pumps & valves)
are gray thicker stuff (schedule 200?).

Asking at a pool store, they said they use gray fittings
near the pump "because they handle heat better".

Yet, that article says both teflon tape and schedule 80 fittings
are a no no.

Interesting though the schedule 40 PVC tensile strength of 7K psi
and the PVC thread "resistance" of 400K PSI.

For 2" pipe, apparently each turn past finger tight adds 0.00239
inches per inch, times that 400K psi, nets almost a thousand psi
per turn (956 psi per turn).

The chart gives us only about 4,000 PSI as the maximum allowable
(3912 psi); so it seems that 4 turns past finger tight is the
maximum one can go with schedule 40 PVC.

In summary, that article recommends, for my 2" PVC plumbing:
1. Pipe dope (not teflon tape).
2. Two turns after finger tight (never more than 4).
3. Only schedule 40 plastic (no schedule 80).

It was also interesting that a single threaded fitting reduces
the strength of the system by half the original strength!

I saw no place that says "no chedule 80". *It says DO NOT MIX 40 and
80 schedule.

Harry K

+1 Good point...

I agree, it didn't say "no sch 80" ..... it said going to sch 80 &
expecting that to avoid a splitting problem was wrong.

Sch 80 will give you higher system pressure & better resistance to
misc mechanical loads
but it won't solve the tape or over tightening problem.

cheers
Bob

On May 11, 12:09*pm, DD_BobK wrote:
On May 11, 10:22*am, Harry K wrote:





On May 11, 7:50*am, Danny D wrote:

On Sat, 11 May 2013 08:22:29 -0500, Vic Smith wrote:
According to this, tape is a no-no
http://www.lascofittings.com/support...tsThreadedPlas...

Interesting conclusions.

I noticed a LOT of my threaded fittings are gray (schedule 80?)
and most of the glued "end" fittings (near the pumps & valves)
are gray thicker stuff (schedule 200?).

Asking at a pool store, they said they use gray fittings
near the pump "because they handle heat better".

Yet, that article says both teflon tape and schedule 80 fittings
are a no no.

Interesting though the schedule 40 PVC tensile strength of 7K psi
and the PVC thread "resistance" of 400K PSI.

For 2" pipe, apparently each turn past finger tight adds 0.00239
inches per inch, times that 400K psi, nets almost a thousand psi
per turn (956 psi per turn).

The chart gives us only about 4,000 PSI as the maximum allowable
(3912 psi); so it seems that 4 turns past finger tight is the
maximum one can go with schedule 40 PVC.

In summary, that article recommends, for my 2" PVC plumbing:
1. Pipe dope (not teflon tape).
2. Two turns after finger tight (never more than 4).
3. Only schedule 40 plastic (no schedule 80).

It was also interesting that a single threaded fitting reduces
the strength of the system by half the original strength!

I saw no place that says "no chedule 80". *It says DO NOT MIX 40 and
80 schedule.

Harry K

+1 * Good point...

I agree, it didn't say "no sch 80" ..... it said going to sch 80 &
expecting that to avoid a splitting problem was wrong.

Sch 80 will give you higher system pressure & better resistance to
misc mechanical loads
but it won't solve the tape or over tightening problem. *

cheers
Bob

I learned _my_ lessong on changing from iron to PVC in the middle of
January with a foot of snow on the ground. I had used a male iron-to-
pvc female. That was out in the middle of a pasture and ovf course
there were no shutoffs on the line anywhere. Future runs I made all
_started_ with a shutoff and 'male irong-female PVC fittings were
banned.

Harry K

On Sat, 11 May 2013 10:22:27 -0700 (PDT), Harry K
wrote:

On May 11, 7:50*am, Danny D wrote:
On Sat, 11 May 2013 08:22:29 -0500, Vic Smith wrote:
According to this, tape is a no-no
http://www.lascofittings.com/support...tsThreadedPlas...

Interesting conclusions.

I noticed a LOT of my threaded fittings are gray (schedule 80?)
and most of the glued "end" fittings (near the pumps & valves)
are gray thicker stuff (schedule 200?).

Asking at a pool store, they said they use gray fittings
near the pump "because they handle heat better".

Yet, that article says both teflon tape and schedule 80 fittings
are a no no.

Interesting though the schedule 40 PVC tensile strength of 7K psi
and the PVC thread "resistance" of 400K PSI.

For 2" pipe, apparently each turn past finger tight adds 0.00239
inches per inch, times that 400K psi, nets almost a thousand psi
per turn (956 psi per turn).

The chart gives us only about 4,000 PSI as the maximum allowable
(3912 psi); so it seems that 4 turns past finger tight is the
maximum one can go with schedule 40 PVC.

In summary, that article recommends, for my 2" PVC plumbing:
1. Pipe dope (not teflon tape).
2. Two turns after finger tight (never more than 4).
3. Only schedule 40 plastic (no schedule 80).

It was also interesting that a single threaded fitting reduces
the strength of the system by half the original strength!

I saw no place that says "no chedule 80". It says DO NOT MIX 40 and
80 schedule.

Harry K
So with Sched 40 pipe, no Sched 80 fittings.right??

On 5/11/2013 7:49 PM, wrote:
On Sat, 11 May 2013 10:22:27 -0700 (PDT), Harry
wrote:
....

I saw no place that says "no chedule 80". It says DO NOT MIX 40 and
80 schedule.
....

Well, that's not QUITE what it says...it says Sch 80 isn't be needed on
Sch 40 properly installed...Sch 80 is overkill but can't really hurt
anything.

So with Sched 40 pipe, no Sched 80 fittings.right??

Can't hurt unless again they're severely over-torqued...

What it's really trying to say is that Sch 40 fittings
_properly_installed_ are all that a Sch 40 system needs to meet the
pressure requirements that Sch 40 is rated to hold. (Which, of course,
only makes sense else't a component would be underdesigned in comparison
with the rest of the same components.)

What they're driving at is as the other responder said above is that the
correct solution to splitting Sch 40 fittings isn't to go to Sch 60 or
Sch 80 and get by w/ over-tightening them but to install Sch 40
correctly instead.

--

On May 11, 6:22*am, Vic Smith wrote:
On Sat, 11 May 2013 04:30:52 +0000 (UTC), Danny D
wrote:









Q: Does the order of the tape & pipe sealant matter?

Starting with this:
http://www2.picturepush.com/photo/a/...g/12901000.jpg

Just wondering, if, for critical 2" PVC applications such as
pool equipment, when using *both* pipe sealant & teflon tape:
http://www5.picturepush.com/photo/a/...g/12900978.jpg

Does it matter if we put the teflon tape first:
http://www3.picturepush.com/photo/a/...g/12901031.jpg

And then the pipe sealant?
http://www1.picturepush.com/photo/a/...g/12901034.jpg

Before screwing the fitting into the housing:
http://www5.picturepush.com/photo/a/...g/12901038.jpg

Just curious:
Q: Does the order of the tape & pipe sealant matter?

According to this, tape is a no-nohttp://www.lascofittings.com/supportcenter/TheDosandDontsThreadedPlas....

Bingo!

Vic has posted an article that would have been my next comment....

The use of tape can lead to splitting of the female threaded fitting.

Loctite makes a product specifically aimed at plastic threads..

No-More-Leaks

As T4 points out, the article notes that threaded joints reduce
pressure capacity by 50% (due to wall thickness reduction).
A side note...in steel piping threading also greatly reduces corrosion
life and that's why we see corrosion evidnence and leaks at the
threaded joints.

Specifically, the article's comments about sch 40 vs 80 were related
to the behavior of threaded fittings.

SInce the threaded behavior & subsequent resulting stress is driven by
the wedging action....
a thicker fitting will be just as stressed (to the first order
approximation) as the thinner sch 40 fitting.
Both are "wedged" open to the same extent when tightened the same
number of turns .

The articles's comment was to emphasize that a thicker fitting is not
the answer.... proper sealant (not tape) is the answer.

cheers
Bob

On Sat, 11 May 2013 12:04:13 -0700 (PDT), DD_BobK
wrote:



The use of tape can lead to splitting of the female threaded fitting.


I've never done plastic plumbing except some glued PVC long ago, but
have dealt some with plastic threaded fittings.
Besides the stress on the female, the threads themselves are much more
easily deformed than galvanized. IOW, strippable. It's too easy to
wrap too much tape on plastic, so my first thought was to just use a
dope that can squeeze out, and relieve stress, Didn't know about
"sealers," but if I worked with plastic I'd find out what to use for
the particular plastic. Trickier than galvanized really, which I've
done a lot of.
There's always some danger listening to "old-timer" advice if they
aren't current on "technology."
I'm a long-time fisherman - like my dad's entire family - and it
wasn't until I started reading fishing magazines that I found out
about the improved clinch knot and started using it.
Told my dad it had something like double the strength of the simple
double overhand knot he used and I had used. He ignored me of course.
Then one time we were fishing in Ontario, and he hooked a big
Northern. Line broke when we almost had it landed.
I showed him the curl at the end of his line where it had broke at the
knot. He used the improved clinch after that.
Now I understand there's something better than the improved clinch
knot. Six-turn San Diego jam.
I'll have to check that out. Sounds interesting.

On Sat, 11 May 2013 04:30:52 +0000 (UTC), Danny D
wrote:

Q: Does the order of the tape & pipe sealant matter?


It matters most about when and where it is applied, which application
is called for - one or the other - not both on the same fitting.

Starting with this:
http://www2.picturepush.com/photo/a/...g/12901000.jpg


Use sealant. I mentioned before about the type for pool pipes.

Just wondering, if, for critical 2" PVC applications such as
pool equipment, when using *both* pipe sealant & teflon tape:
http://www5.picturepush.com/photo/a/...g/12900978.jpg


Are those for PVC pipe?

Does it matter if we put the teflon tape first:
http://www3.picturepush.com/photo/a/...g/12901031.jpg

And then the pipe sealant?
http://www1.picturepush.com/photo/a/...g/12901034.jpg


Is that applied over the tape? What a hoot.

Before screwing the fitting into the housing:
http://www5.picturepush.com/photo/a/...g/12901038.jpg


Aw heck Danny, put a second coat on there HOOT

Just curious:
Q: Does the order of the tape & pipe sealant matter?

Not much matters after 4-5 good coats of each.

You outdone yourself this time

On Sat, 11 May 2013 11:44:48 -0700, Oren wrote:

You outdone yourself this time

I'm actually surprised that I apparently put too much on,
according to your comments.

I thought that's how much you're supposed to use.

On Sat, 11 May 2013 19:04:51 +0000 (UTC), Danny D
wrote:

On Sat, 11 May 2013 11:44:48 -0700, Oren wrote:

You outdone yourself this time

I'm actually surprised that I apparently put too much on,
according to your comments.

I thought that's how much you're supposed to use.

You never said if the pipe dope was on over the Teflon. It sure
appeared that way or my inference from the photos. More is not always
better.

Again. Is the sealant you used intended for PVC pool pipe fittings?

On Sat, 11 May 2013 12:34:33 -0700, Oren wrote:

Again. Is the sealant you used intended for PVC pool pipe fittings?

I called RectorSeal while I was at Home Depot and they said to use
the red tube that I bought (and not the red jar, which was for metals).

The red tube says it's for "plastics", so that's what I used over the
Teflon tape.

Now I understand, from Vic Smith's article, that Teflon tape is a no-no;
and I understand that *lubrication* is a no no ... so it appears *all*
the tubes of sealant I bought from Home Depot are wrong.
http://www5.picturepush.com/photo/a/...g/12900978.jpg

I wonder if the local plumbing and irrigation supply places know this
stuff?

Danny D said:

No.

The way I read that Lasco article, you should not be using EITHER pipe dope OR teflon tape on plastic pipe threads.

You should be using a thread sealant meant for plastic threads ONLY. Don't use it with teflon tape because that teflon tape on the male threads is going to cause more stretching of the female threads around them. With metal threads, that teflon tape doesn't matter, but with much weaker plastic fittings, three or four wraps of teflon tape is enough to cause significantly more stretching of the female thread than they were designed to handle. AND, way more compression than you need to prevent leaks.

From my reading of that Lasco article, you should apply thread sealant meant for plastic threads to your male plastic threads, and then screw on the female plastic fitting. Tighten to finger tight and then no more than two full turns after that. Then stop, and move on to the next plastic threaded joint. That's all you need to do, supposedly, to get a leak free threaded plastic joint.

If you've already used teflon tape on your threaded plastic joints, and there's no splitting or leaking, I would just leave them as they are. But, in future, just use the red bottle that says it's meant for plastic and don't use it with anything else.

At least that's what I got out of that Lasco article when I read it. Maybe re-read it with what I said in this post and my previous post in mind, and see if it makes more sense. Ignore that part where he starts talking about doing stress calculations. The part that reads:

"Stress" (tensile stress) is the force exerted by the strain of the male thread multiplied by the resistance of the PVC. The resistance of PVC is 400,000 pounds per square inch (psi). The strain per turn past finger tight for one-inch PVC pipe is .00447, so the stress per turn is 1,788 psi. Thus, a one-inch threaded PVC joint that is tightened four turns past finger tight will develop a tensile stress of 7,152 psi. The joint is bound to fail since the stress exceeds the 7,000 psi tensile strength of PVC, without even adding the tensile stress caused by the pressure inside the irrigation system (up to a maximum of 2,000 psi).


Ignore that part. It's hard for anyone who hasn't taken engineering to understand, and he's not even using proper terminology. He's saying the "resistance" of PVC is 400,000 psi, when he should be calling that the "modulus", or more correctly, the "Young's Modulus" or "E" of PVC is 400,000 psi. Also, he's saying that the strain is ".00447" without explaining what he means by that. Most people would be expecting a unit of some sort after that number, but strain is a dimensionless number, like percent. It's actual dimensions are inches per inch, or centimeters per centimeter or miles per mile or lightyears per lightyear. If you stretch a 8 foot long board by 27/64ths of an inch, you've put a strain of 0.00447 into it cuz 27/64ths of an inch divided by 8 feet is 0.00447 (within round-off error).

All he's saying is that each turn past finger tight of a 1 inch tapered male NPT thread into a female NPT thread will stretch the female thread plastic by about 1/2 of one percent (actually .447 of one percent), which when multiplied by 400,000 psi per 100 percent is enough to put about 2000 psi of stretching force into the female plastic thread. So, four turns will give you 4 times as much, or 8000 psi of stretching force, and that's gonna split the female fitting because PVC plastic breaks at 7000 psi of stretching force.

That's all that gobbeldygook is saying.

So, just read the rest of that article with the horse sense in mind that the more tape or dope you apply to a male tapered thread, or the more you tighten a male tapered thread, the more stretching force you'll cause in the female tapered thread it's screwing into. THEN, that article should be easier to understand. And, keep in mind that when he says "thread sealant", he's talking about a special sealant meant for plastic threads, NOT pipe dope.

Read it again and tell me if you don't agree that, according to Lasco, you should be using the stuff in the red bottle labeled "For Plastic" and ONLY that stuff. If you're still confused by something in that article, quote it and I'll try to explain it.

On Sun, 12 May 2013 04:49:41 +0000 (UTC), Danny D
wrote:

Now I understand, from Vic Smith's article, that Teflon tape is a no-no;
and I understand that *lubrication* is a no no ... so it appears *all*
the tubes of sealant I bought from Home Depot are wrong.
http://www5.picturepush.com/photo/a/...g/12900978.jpg

The T plus 2 should work. It is for PVC, does have some Teflon -- BUT!

(also from the LASKO link)

"...A sealing compound must be compatible to plastics. Many brands of
pipe sealant contain oils, solvents or carriers that can damage
plastic. A proper sealant must be certified by the manufacturer to be
harmless to the fitting material and to not contaminate fluid in the
pipe.

Finally, a sealing compound must not lubricate the joint to the point
that over-tightening is encouraged. Several sealants on the market
meet all these requirements."

....
I would trust the T plus 2, just do not over tighten because it does
have some Teflon in it...

On Sun, 12 May 2013 04:49:41 +0000 (UTC), Danny D
wrote:

On Sat, 11 May 2013 12:34:33 -0700, Oren wrote:

Again. Is the sealant you used intended for PVC pool pipe fittings?

I called RectorSeal while I was at Home Depot and they said to use
the red tube that I bought (and not the red jar, which was for metals).

The red tube says it's for "plastics", so that's what I used over the
Teflon tape.

Now I understand, from Vic Smith's article, that Teflon tape is a no-no;
and I understand that *lubrication* is a no no ... so it appears *all*
the tubes of sealant I bought from Home Depot are wrong.
http://www5.picturepush.com/photo/a/...g/12900978.jpg

I wonder if the local plumbing and irrigation supply places know this
stuff?
Just because the recommended red stuff works as a lubricant doesn't
mean it's not the right stuff. Virtually ANY sealant will "act as" a
lubricant.

Since most plumbers I know still use teflon tape on plastic threads, I'd say no.

The people working the counter in plumbing wholesalers won't be plumbers. They may have gotten that job because they have some sort of plumbing related experience, but nobody is going to work for minimum wage working the counter at a plumbing wholesaler if they can make several times that wage working as a plumber for a plumbing company.

On Sat, 11 May 2013 11:44:48 -0700, Oren wrote:

http://www5.picturepush.com/photo/a/...g/12900978.jpg
Are those for PVC pipe?

While I was in Home Depot, I had called the rectorseal.com 800 number,
and asked what I should use in pool plumbing (800-231-3345).

The guy that answered for technical support didn't really sound all
that knowledgeable, but, he must have known more than I.

He's the one who suggested the red tube you see in the photo.

However, after reading Vic Smith's article, I understand that I don't
want something that lubricates.

I just want sealant.

So, I think *all* the solutions in that picture are wrong.

On May 12, 12:46*am, Danny D wrote:
On Sat, 11 May 2013 11:44:48 -0700, Oren wrote:
http://www5.picturepush.com/photo/a/...g/12900978.jpg
Are those for PVC pipe?

While I was in Home Depot, I had called the rectorseal.com 800 number,
and asked what I should use in pool plumbing (800-231-3345).

The guy that answered for technical support didn't really sound all
that knowledgeable, but, he must have known more than I.

He's the one who suggested the red tube you see in the photo.

However, after reading Vic Smith's article, I understand that I don't
want something that lubricates.

I just want sealant.

So, I think *all* the solutions in that picture are wrong.

All I can tell you is that there are a hell of a lot of people using
teflon tape and not having problems. I think the Lasco
article makes sense and a thread sealant is probably
better. But in the grand scheme of things, I'm not sure
it makes a huge difference. To get the high pressure to
crack a fitting, you'd probably have to over tighten the
fitting. If you know what you're doing, that isn't likely to
happen.

Here's a source that says sealant is preferred, but if
you have to, you can use tape:


http://www.spearsmfg.com/how_to/FG-3...06_English.pdf

On Sun, 12 May 2013 05:29:15 -0700, wrote:

in the grand scheme of things, I'm not sure it makes a huge
difference.

I don't disagree - and - I'm a big believer in doing it any way
you want - BUT - only after knowing the right way to do it -
and not out of sheer ignorance (which was what I was doing).

Since this is alt.home.repair, I agree we should at least
discuss and know HOW to do it right.

At this point, we know that the correct way to do it is not
with Teflon tape, and certainly not with BOTH tape & sealant.

Also we know that the right way is to use a * non-lubricating *
sealant, which is actually hard to find at the big box stores.

http://www.spearsmfg.com/how_to/FG-3...06_English.pdf

This confirms a few things in the Vic Smith article.
- Teflon tape is deprecated
- Teflon tape is a lubricant
- Never use both Teflon tape and sealant paste
- Tighten 2 to 3 turns past finger tight

It looks like huckleberries are in season, as the "right stuff"
is the "Blue 75 thread sealant". I'll see if Home Depot has the
stuff in stock.