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, 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 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 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 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 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 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 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 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

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 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 May 11, 9:03*am, dpb wrote:
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.

--

+2

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, 9:03*am, dpb wrote:
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.

--

dpb-

I was wondering if they were only looking at stress induced from
tightening
& doing their tightening stress approximation as merely an E * radial
strain based wedging action?
Would that not be independent of wall thickness?

Total fitting load is tightening load + pressure load.

Of course the system pressure capacity would be higher with Sch 80 vs
sch 40
but perhaps they were trying to emphasize the point that sch 80 was
not more over-tightening resistant than sch 40?

Am I missing something here?

cheers
Bob

On 5/11/2013 2:17 PM, DD_BobK wrote:
....

I was wondering if they were only looking at stress induced from
tightening & doing their tightening stress approximation as merely an
E * radial strain based wedging action? Would that not be independent
of wall thickness?

The _loading_ is same because the dimensions are the same but the stress
is per unit area and there's more material so the actual stress is lower.

Meself, I think they just blew it on that part...

The weakest link in a Sch 40 threaded joint w/ a Sch 80 fitting will
still be the section of threaded Sch 40 not inside the fitting (think of
a female coupling/tee, say, w/ a male pipe for example).

Certainly it is true one doesn't want to over-torque a plastic fitting,
particularly the female that is in tension but it certainly is not true
that the same stress at the same thread depth on a Sch 80 has the same
stress as a Sch 40 because it does have that extra thickness.

--

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 5/11/2013 2:32 PM, dpb wrote:
....

Being as the following was my posting I'll edit it a little in place...

Certainly it is true one doesn't want to over-torque a plastic fitting,
particularly [since] the female is in tension but it certainly is not true
that the stress at the same thread depth on a Sch 80 has the same
stress as a Sch 40 because it does have that extra thickness.

The above previously wasn't written very well, unfortunately. I recast
it some while writing and didn't get all the edits that could intended
done, sorry. I made a couple of minor fixes above that at least help
but I'll not worry about it further...

I'll just add that loading--force; stress-- force/unit area. The
geometry (hence tightening) controls loading of this portion of the
total load; they're correct there. But loading isn't the same thing as
stress; it's only the numerator.

--

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.....

No, I don't think your missing anything. If anything, they're saying that ANOTHER reason not to use Schedule 80 female fittings is because their greater strength tempts people to tighten them more because they know they'll stand up to the greater hoop stress without splitting, and that's NOT what they want you to do.

The point they're trying to hammer home is that it's the use of pipe dope and teflon tape on plastic male NPT threads that increases the wedging force of the male pipe thread as it's being tightened, and that increases the hoop stress in the female fitting, and that's what causes the female fitting to split, and that problem can be entirely avoided by using a thread SEALER meant for plastic pipe treads on the male NPT threads instead of either teflon tape and/or pipe dope.

They're saying that plastic NPT threads don't need the lubrication provided by teflon like metal NPT threads do, and so all the teflon tape or pipe dope does is increase the hoop stress on the female fitting causing it to split. By using a thread sealer meant for plastic NPT threads, you avoid increasing the hoop stress over what the female fitting was designed for, and that eliminates the female fittings splitting when you screw the male fitting in.

So, the admonition against switching to Schedule 80 female threaded fittings is that it's not addressing the real problem. If the square peg won't go into the round hole, you need to realize that you need a round peg, not a bigger hammer. In this case, the analogy is that if your female NPT threaded plastic fittings are splitting, you need to realize that the cause is the pipe dope or teflon tape your using on the male pipe treads, and you need to use a thread sealant meant for plastic threads instead, not use a bigger and stronger female fitting.

On 5/11/2013 4:37 PM, nestork wrote:

DD_BobK;3060537 Wrote:

I was wondering if they were only looking at stress induced from
tightening& doing their tightening stress approximation as merely an E
* radial
strain based wedging action?
Would that not be independent of wall thickness?

Total fitting load is tightening load + pressure load.

Of course the system pressure capacity would be higher with Sch 80 vs
sch 40 but perhaps they were trying to emphasize the point that sch 80
was
not more over-tightening resistant than sch 40?

Am I missing something here?

Bob


They're just saying that using Schedule 80 fittings is treating the
symptom, not the disease. They're saying that the disease of plastic
female threaded fittings splitting when tightened can be cured by using
a proper thread sealant instead of using pipe dope or teflon tape on
plastic threads.

They're saying that the use of either teflon tape or pipe dope on
plastic threaded fittings will increase the wedging action of the male
pipe threads, thereby increasing the liklihood that the female fitting
will split.

So, the admonition against switching to Schedule 80 female threaded
fittings is that it's not addressing the real problem. If people used a
thread sealant instead of pipe dope or teflon tape, there wouldn't be
the increased splitting force on the female fitting, and there wouldn't
be any splitting problem. So, switching to Schedule 80 female plastic
fittings to avoid splitting is not really solving the problem. The real
solution is found in using thread sealant instead of pipe dope and/or
teflon tape to avoid the splitting problem altogether, rather than buy
stronger fittings that will stand up to the greater splitting force.

Basically, if the square peg won't go into the round hole, you need to
realize that you need a round peg, not a bigger hammer. In this case,
the analogy is that if your female plastic fittings are splitting, you
need to realize that the cause is the pipe dope or teflon tape your
using, and you need to use thread sealant instead, not use a stronger
female fitting.

or they're being over-torqued if not using tape or metal pipe dope.

That's a better summary of the point they're trying to make than
theirs...

Now granted the _strain_ is the same as it's the dimensionless ratio of
the distance moved/turn and the geometry of a Sch 40 or Sch 60 or 80
fitting is the same so the geometries do cancel out. But the _stress_
in psi induced by that same strain is less for the fitting with more
material in it--if that weren't so it wouldn't be possible to design for
higher pressures by adding material because it wouldn't matter is the
conclusion that statement leads to. That clearly just isn't so so
they've confused the writeup in that regard.

Granted the weak point is as they state w/ the notching effect of the
threading but there's still significantly more material left behind in a
heavier fitting than the lighter and that does make a difference.

Certainly it shouldn't be/isn't necessary to use heavier fittings if
properly assembled (or the matching fittings are under-designed) is
their main point and that anything that actually causes deformation of
the fitting is detrimental. Those are certainly common sense
conclusions as well.

--

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 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??

When I wrap myself in teflon tape, I slide off the chair and under the table.
..
Christopher A. Young
Learn more about Jesus
www.lds.org
..
..
"Robert" wrote in message ...

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

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, 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 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 23:37:04 +0200, nestork wrote:

If people used a
thread sealant instead of pipe dope or teflon tape, there wouldn't be
the increased splitting force on the female fitting

Your summary was fantastically well written and easy to follow!
(much easier than the original article)

It's clear I should not be using Teflon tape.

But which of the non-lubricating "sealants" should I be using then?
http://www5.picturepush.com/photo/a/...g/12900978.jpg

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 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.

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 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 04:36:17 +0000 (UTC), Danny D
wrote:

On Sat, 11 May 2013 23:37:04 +0200, nestork wrote:

If people used a
thread sealant instead of pipe dope or teflon tape, there wouldn't be
the increased splitting force on the female fitting

Your summary was fantastically well written and easy to follow!
(much easier than the original article)

It's clear I should not be using Teflon tape.

But which of the non-lubricating "sealants" should I be using then?
http://www5.picturepush.com/photo/a/...g/12900978.jpg

The T plus 2 looks like it will work:

"RectorSeal T Plus 2 pipe thread sealant is a non-setting,
multi-purpose compound which contains PTFE, plus synthetic fibers to
create a stronger seal. Recommended for use on threaded galvanized
steel, iron, brass, copper, aluminum, stainless steel, polyethylene,
fiberglass reinforced, PVC, CPVC, and ABS pipe. T Plus 2 may be
pressurized immediately following application. Conforms to TT-S-1732."

The RectorSeal TRU-BLU I mentioned will also work:

"RectorSeal® Tru-Blu™ pipe thread sealant with PTFE is a fast-dry,
flexible set thread sealant designed for high vibration environments
such as refrigeration and industrial applications. PTFE has been added
to enhance thread lubrication during assembly and break out.
Recommended for use on threaded galvanized steel, iron, brass, copper,
aluminum, stainless steel, polyethylene, fiberglass reinforced, PVC,
and CPVC pipe. Great for use as a positive lock and seal on threaded
fasteners. Certified to NSF/ANSI 61-G"

Both have some amount of Teflon in them.

Isn't the No.5 for metal pipe thread?