I'm installing this (http://www.moen.ca/adler/chrome-posi-temp-r-tub-shower/_/R-CA-CONSUMER%3AL82839) Moen shower head and handle, and making changes to the existing plumbing in a basement renovation. I have all the copper piping where I want it and connecting to the threaded copper connectors that attach to the brass valve housing. There are no leaks in any of my joints or copper connections. I do have an issue where the copper connectors thread into the brass value. There is a slow leak on the left hand connector (picture below).

This is about the third time I've sweated one side's copper off so I could turn the threaded connector out of the valve, reapply teflon tape, screw the connector back into the valve, and then re-solder the piece back to the rest of the copper. Each time while screwing the piece back in, the valve has turned a little bit as I get the connector light. I then turn it back so that it will be flush with where my concrete board will eventually be in the shower. When I insert the cartridge to test the pressure, the opposite connector then shows a slow leak and I'm back where I started: a slow leak and everything soldered in place with no way of fixing the leak without sweating off another joint, prepping everything again and hoping for the best the next time I turn the water on.

Obviously, I won't stop till I don't have any leaks. The next time I do this I think I will remove both sides from the housing and reapply teflon tape to both, screw them in and then reattach to the other copper pipes. That is, unless anyone has a better suggestion. Am I missing an obvious fix I can make without re-soldering? I will probably need to buy some new 90 degree joints and cut more pipe, as after a number of redos (sanding down the copper ends each time, excess solder, etc) I'm losing confidence in the fittings that are currently working fine.

So, I'm looking for advice on the above, and also wanting to ask the obvious question that arises with these types of brass valves. Why are there threaded female connections on the valve if when you over-turn one side ever so slightly too far, you end up with a leak and problem like I have? Wouldn't a soldered joint be the best for connecting to the valve? Or, and I'm not ruling this out, am I just doing it wrong?

Thanks in advance for any help.

If it wus me,

I'd heat and knock off the 90's, unscrew the adapters and discard every thing. Fittings are not that expensive to be wasting time with. Clean up your supply pipe. Heat, wipe off with wet cloth, sand to insure new 90 will slip on easily. Cut two pieces of pipe about 6" long and solder an adapter on each one. Screw the adapters (with the short pipe) into the valve using pipe dope. Put a wrench on one to hold it and use another wench to tighten the other. Sounds like you are not tightening the adapters enough. I prefer pipe dope when you have a problem but if you are going to use Teflon tape use at least 4 wraps. Neither pipe dope or Teflon tape are sealers, they are lubricants. After you have set up your valve, cut you pipe stubs to length and solder new 90's to the pipe stubs and your supply lines.

Joe, is there room to work in a union?

You cannot solder with teflon tape on threads this close to the flame. That's why it leaks. What happens is that when you apply heat teflon tape shrinks losing its sealing properties. Use Pipe Dope paste. Pipe Dope will withstand heat.

If you really want to use teflon tape than make a cut about 6" up the vertical pipe. Unscrew the Female adapter and 90 in one piece, re-apply teflon tape, crew it back in ( in one piece ). Put wet rag over the threads. Now, take a copper coupling and solder the cut at vertical pipe.

Back to you. Milo

Had the same problem. Consulted an expert, who said "brass on brass". Buy brass threaded unions, not copper. Use pipe dope. Tighten as much as you can.

Brass on brass sounds fine, but you'll still need to transition to copper at some point using copper fittings to that brass union... ;)

The fact is that the installation was done wrong, and it wasn't the copper male adapters into the brass valve body that was the issue here...JP just soldered the adapters in place and you can't do that! Here, male adapters must first be sweat/soldered and then left to cool BEFORE installing into the valve body.

Once again, for future readers, using copper male adapters into brass valves is just fine!!

Thanks!