Help with connections at one handle valve! At wits end...

[cbass]

Making up tub/shower tree for new one piece unit. Using CPVC. My glued connections are great, but the CPVC to brass fittings are leaking where they connect to the Moen 4 way valve at control. Tried 2 wraps of tape, also tried good amount of teflon compound only. I've had to remake the whole setup three times and keep getting small leaks at the threaded male to female valve connections. I've got them tightened till about 3 threads are visible, still no luck. Its driving me bonkers. Its our only bathroom, so I'm under the gun. Any help much appreciated. Thanks.

 

[Jadnashua]

Another wrap of teflon AND some pipe dope might work. Are you sure the threaded connections are tapered and not straight? If they are straight, they require a washer or gasket, and you won't be able to make a good seal with tape or dope. If the fitting is bottoming out, something is wrong. If it is getting tight, you may not be tightening it enough.

 

[Sponsor]

 

[cbass]

Tapered or Straight?

I assume they are tapered. No gaskets or washers. The only thing I can think of is bad female threads on the Moen unit. I actually got a semi-pro plumber to assist, and his connections did the same thing. I'm tearing everything out again and replacing the moen valve. Any other ideas?

 

[Jadnashua]

They usually are, but I've seen straight threads on shower valves. Does it get tight before bottoming out? Are you sure the fitting isn't cracked? There could be a pinhole leak in the casting.

Did you try both tape and dope?

 

[cbass]

Tried new Moen valve...nothing

Actually worse than before. I think I might have a bad batch of fittings. Now I'm trying a different supplier, not Lowes or Home Depot. Round 4.

 

[cbass]

OK, new fittings..so for so good.

scrapped the fittings from Lowes. Went to local Ferguson store. I found some CPVC to brass fittings that have more of a square brass edge at the end of the threads. The other fittings I was using had a beveled "seat" at the end that seemed like they needed to mate with a similarly beveled "seat" at the bottom out point of the threads. Also changed to a thick black thread compound that seemed to do the trick. I've talked to countless "experts" that can't come up with a reason as to why the original fittings I was using wouldn't work with normal tape and white compound. Leak free so far today. One other interesting tidbit, the old fittings actually held water on the last attempt until I redirected water to the shower, then the cold and hot supply leaked at the threads into the mixer valve. Strange. Worked for faucet but not when shower was used. Anyway, hopefully this new setup continues to work. Thanks very much for trying to help a brother out.

Cbass.

 

[hj]

threads

I've seen straight threads on shower valves

never on one made in the USA. European metric ones maybe.