Expert: Dana Bostick - 7/7/2009

Question
I have recently installed some copper fittings and due to the ancient plumbing in my house, I had to use a threaded insert into a copper "T" to connect a female fitting to the female side of the "T". Prior to putting the insert in to the "T", I wrapped the threads in teflon tape and then put it all together. It seems to work pretty well, but I have noticed a small drip that comews out of that junction at the rate of one drip every minute or so. Was there something I missed? I tightened it as tight as humanly possible. Was there some sort of fitting compound I was supposed to put on first, and is there something that I can put on afterwards to keep this from happeneing. Normally I would lag it and let it evaporate, but the area of this drip is usually quite damp and I'm worried that it won't evaporate in time.

Answer
Hi Matthew,
I'm not a fan of Teflon tape although I have used it occasionally. Pipe threads are tapered and I think think over tightening just squooshes the tape out of the joint.  Also, one or two wraps is the recommended amount and most people I've seen use many more.  The exacerbates the problem.  I prefer a paste with Teflon in it to the tape.

There is not a lot you can do about it now, after the fact other than re-do the joint. As long as it's wet, you will not find much that will stick to it.  I have used a two-part "marine epoxy" putty with some success.
Good Luck,
Dana