Expert: Sharon McCarthy - 11/1/2009

Question
Hello Sharon,
I am installing the drain lines for a 5 piece bathroom in the top floor of a 1928 house with 2x6 floor framing. I am building box beam ceilings to conceal the P trap for the claw foot tub. There will be limited access to this P trap once it is installed so I am wondering if I use glue or tape on the flexible nut on the P trap.
Thanks in advance for your response.

Answer
Dear Jody, Good question! Most P traps have what are called compression fittings, a threaded nut and a cone-shaped plastic washer, and on the P part of the trap the small end of the P is a rounded shape that fits precisely into the other part, and again is tightened down with a threaded nut.

  You shouldn't use glue on these fittings. Glue will solidify very quickly, so if the nut didn't go down all the way this could cause a leak. You can use teflon tape on the threads but it isn't necessary.

  Another alternative would be to use an ABS trap that is designed to be glued together at all joints rather than a trap as you described with threaded nuts. Shower drain traps are solid glued traps. This is done for the same reason, once a shower floor is installed the trap is inaccessible. Also you'll find those same kinds of traps, solid glue traps, on washing machine drain pipes, right at the bottom. These pipes are usually set back into the wall so again, the trap can't be reached without cutting into the wall.

  My suggestion is to ask at an Ace Hardware. Ace stores carry all fittings, plus the people who work at Ace stores are there to help you find exactly what you need. Tell them what you have planned and they can show you the parts you need. Hope this helped!!  Sharon