Tightening PVC to Brass 1

[Keyho]

This is a fairly simple question I think but the answer has been anything but obvious to me. I am tightening 1 1/4 inch PVC nipples to female brass fitting openings and often seem to have a small leak problem. Do I just keep tightening as with galvanized nipples? I am aware of never over tightening metal male nipples to female PVC fittings. But with PVC MIP to brass FIP, how tight is usually acceptable? Two or three threads showing as with MIP to FIP galvanized connections? How strong are PVC male thread nipples anyway? Is Teflon tape the best thread sealant or Teflon paste?

Thanks for any help on this not so simple query
Keyho

 

[MikeHalloran]

PVC fittings are pretty strong, but they are still plastic, and will behave, well, plastically.

I've used TFE tape on PVC fittings with okay results, but I like RTV silicone better. Clear always looks icky, to use the technical term. White or black look better to me.







Mike Halloran
Pembroke Pines, FL, USA

 

[STYMIEDPIPER]

I agree with MikeHalloran
I like teflon tape. It gives a nice professional appearances.
If it has threads I always use teflon tape which is not always the recommended practice.
I became tired and fustrated everytime I had to disassemble a threaded joint, dry the threads, and attemept to reseal and tightened the joint. Finally I decided teflon on all threads.

 

[stanlsimon]

I always try to install a union next to the pvc threaded connection due to the condition you described, the union let you retighten the joint without dismantling everything.

I have had to tighten down to almost no exposed threads to get them to stop leaking. That is with a good coating of rectorseal.

 

[FACS]

I use mostly paste, I feel that it spreads in the threads better.

Metal on metal I usually use tape.

Plastic on plastic it doesn't seem to matter, I've used RTV quite a bit, it's my best friend, but for a plastic in metal fitting I'd use the paste.

There is one camp that uses both. I knew a guy that insisted on a layer of tape over the paste.

The bottom line is that it does not matter, just use something. The plastic fitting will turn until it breaks. If you use paste or tape and it still leaks, and there are no threads left, then something else is wrong. You could use RTV as a fix, but I'd tend to say that there is another problem.

Maybe try replacing both fittings, if possible. I've had galv fittings leak from cracks, oversized threads, pinhole corrosion.

Charlie

http://www.facsco.com

 

[pvcman]

Plastic fittings are tappered tightning these fittings will only cause more stress and more leaks. Not all pastes are recomended for plasitc piping. would recomend you talk to a plastic professional.

http://www.harringtonplastics.com

has a industrial engr guide for all kinds of plastics.
Normally teflon tape hand tight quarter turn should do it.
There are several Mfgs. making reinforced fittings for thrd. Spears and Ipex.