Threaded PVC problem

[stugray]

CeeGee,

"Worked flawlessly!"

SO you were able to tighten two "Pipe fittings" until there were no threads showing?

Again, I would like to see a picture.


In my experience, you will spilt the female fitting before you get anywhere close.

"Looks like someone owes you an apology"

It appears that we misunderstood the question.

It is IMPOSSIBLE to thread a MPT 100% into a FPT fitting for that would defeat the purpose.

If you did so, then I will apologize to luv951 and never buy that brand of PVC fitting.

Stu

 

[stugray]

Ok,

Official apologies to luv951.

I just, as an experiment, took two 1-1/4" PVC threaded fittings, and I WAS able to tighten them 100% and then loosen them without breaking.

I used teflon paste, a few grunts & farts ( maybe even a hernia ).

So... it is possible.

However it is never a good idea to overtighten PVC threaded fittings.
Most of the time they break immediately and often days or years later.

So for CeeGee.s application, no worries it is not under pressure.
Glad you could make it work.


luv951 - Sorry you were correct.
I will curtail my use of the word "Impossible" ( you think i'd have learned by now ;-)

Stu

 

[luv951]

stu - no worries at all. I appreciate you owning up. Its all kewl.

 

[dogstar74]

Oh man, I was about to get out a picture. "Only a sith lord works in absoultes"

Just kidding, Even though it's not impossible, it's dang near impossible. I'm sure that's what you meant Stu.

Aaron

 

[BeanAnimal]

If you take a look back at what I said...

The teflon tape greatly increases the lubricity between the parts, allowing them to be severely overtightened. This puts tremendous stress on the female part. The stress may break the part immediately, or some time down the road.

In this case, a cracked fitting will not likely be a problem. However, the important information to walk away with is that it is NOT good practice for fittings that will be a problem if they leak

 

[luv951]

<a href=showthread.php?s=&postid=15049307#post15049307 target=_blank>Originally posted</a> by BeanAnimal
If you take a look back at what I said...

The teflon tape greatly increases the lubricity between the parts, allowing them to be severely overtightened......However, the important information to walk away with is that it is NOT good practice for fittings that will be a problem if they leak

Agreed. This is why you need to add leverage with some sort of extended handle to get the part to twist in.

 

[BeanAnimal]

I think you entirely missed the point... your statement is not in agreement with what I was attempting to convey

Without the tape, the fittings get tight very quickly, this is because they are tapered. By using the PTFE tape or paste, the parts are lubricated and can be tightened much further, putting tremendous stress on them.

When assembling threaded PVC parts, one should hand tighten the parts without tape or paste, counting the number of turns. Once the parts are dry fitted they should be disassembled and taped (or doped with paste). Final assembly should be done using the same number of turns that created a tight dry fit and then another 1 to 1.5 turns max. Going any further deforms the fittings and can cause more of a chance of leaking and/or part failure (immediate or future).

 

[dogstar74]

I agree that is the important information to take away, and if I ever have an application that I NEED to have the threads fully enclosed, I always take a trip down the electrical isle and use the grey fittings.

Not for arguement's sake, but for information sake, the last time I bottomed out a NPT 1/2 schedule 40 fitting with TFE tape, it was not on purpose, and I really didn't have to force it too much. I was just tightening it down and then "wow, it went all the way in." Then I thought to myself, "Boy that looks pretty sharp!"

L8R
Aaron

 

[BeanAnimal]

Yup it depends on the tolerances and manufacture of the fittings. That is also why threaded PVC (especially in sizes less than 4" or so, pretty much sucks. The cast threads are just not accurate and shrinkage, mold flash and design tolerances make things unpredictable. FWIW PTFE paste is almost always a better idea than the PTFE tape

 

[luv951]

<a href=showthread.php?s=&postid=15049568#post15049568 target=_blank>Originally posted</a> by BeanAnimal
I think you entirely missed the point... your statement is not in agreement with what I was attempting to convey

Actually, I think you are assuming too much about my posts.

This thread has been about fully seating threaded PVC for a stand. Not a pressure application. The OP just wanted to know how to make his stand level. The assertion that fully seating a threaded PVC is "impossible" is wrong. I was merely helping the OP accomplish the task that he needed help on. Never made any assertions or claims as to whether one would want to, or should want to, fully seat threaded PVC in a pressure situation. In that regard, I agree with you.

 

[BeanAnimal]

<a href=showthread.php?s=&postid=15051466#post15051466 target=_blank>Originally posted</a> by luv951
Actually, I think you are assuming too much about my posts.

No, I read them word for word without assuming anything. If you meant differently, then your meaning was not clear

This thread has been about fully seating threaded PVC for a stand. Not a pressure application.

I am very aware of what the thread is about. The advice I offered (and Stu offered) was given as "best practice" advice to aid those who read [sic] "put tape on the pvc fittings and crank them down with a cheater bar until they bottom out" and then subsuquently applied that advice to their PLUMBING as well. I made my context very clear.

The OP just wanted to know how to make his stand level. The assertion that fully seating a threaded PVC is "impossible" is wrong.

I, in no way said, implied or aluded to the notion that fully seating the threads was "impossible" or even hard. I simply said that overtigthening threaded PVC fittings puts tremendous stress on them and leads to deformation and/or failure. I offered a general rule of thumb to judge how far to tighten them in a plumbung situation and also offered that for OPs purpose, a cracked fitting would likely not make a difference.

I was merely helping the OP accomplish the task that he needed help on. Never made any assertions or claims as to whether one would want to, or should want to, fully seat threaded PVC in a pressure situation. In that regard, I agree with you.

Nobody has faulted you for helping. A few of us have simply offered to put context to the advice in hopes of helping the OP and others understand the ins and outs of threaded PVC connections. If you agreed with my advice, your post did not convery that meaning very clearly at all.

No hard feelings, we are all on the same side here (trying to help people learn how to do things correctly).