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