Metal and PVC Threads

[carlyai]

I have an encapsulated female PVC thread that I want to screw in a male metal thread connector. Just reading that this union will probably leak. The article says that female metal thread to male PVC thread won't leak, but the other way will.

I can't change the female threaded part as it's fiberglassed into my fish tank sump. The male metal connector is the only one I could find that goes to PP-R pipe.

What's your experience going from female PVC thread to male metal thread. Did it leak? 

[Crossy]

Loads of PTFE tape and at the relatively low pressures associated with a fish tank you should be good to go.

 

I'm  trying to think if I've ever done one that way round, I don't think I have.

 

[carlyai]

15 minutes ago, Crossy said:

Loads of PTFE tape and at the relatively low pressures associated with a fish tank you should be good to go.

 

I'm  trying to think if I've ever done one that way round, I don't think I have.

 

Thanks. That's what I was thinking, loads of tape, and I can't remember if I've done one like that either.

[petermik]

7 hours ago, carlyai said:

Thanks. That's what I was thinking, loads of tape, and I can't remember if I've done one like that either.

You could always put some silicone sealant in the threads if you have some handy...and providing you want a more permanent seal

[carlyai]

15 minutes ago, petermik said:

You could always put some silicone sealant in the threads if you have some handy...and providing you want a more permanent seal

Yes or apoxy it all together.

[VocalNeal]

The reason for the compatibility advice is because the female PVC will expand. The key here is your pressure which is negligible for a fish tank or rather the key is remembering that fact. You are not putting wheels on a bus so you don't need to over tighten the connection. Some liquid sealant on the joint will be better than thread tape. Thread tape just increases the diameter of the male part which aggravates the problem. 

 

Do the joint up tight by hand and then add, say, 1/4 turn. Again it is not a bus.

 

If the female part protrudes enough you could add a pipe clamp to the outside for belt and braces.

[lopburi3]

Not a good match - suspect it is the reason plastic female connectors normally have a metal insert.  Decades ago tried and failed and have always made sure to buy connector with metal insert since.  Might be worth getting a plastic male to female/metal insert connector?