In connecting my 3/4 copper supply to a heat exchanger, I had to use 3/4 female adapters to make the connections. I used thread tape and tightened the adapters about as much as I could with a crescent wrench.
The first time both connections leaked – just a small drip, but enough to be a problem. I cut the lines, removed the fittings and re-wound the thread tape and then tightened the fittings onto the heat exchanger, tighter than first time, I think. Same problem – slow drip on both.
Is there something better than thread tape – plumbers putty for example? Or is the thread tape the problem. I am not a plumber but I have plumbed my whole house with a number of threaded fittings and no problem on any of the others.
Any Thoughts?
Bob
Replies
Next time sweat in a coupling on each line. Then, if a 3/4" brass sweat-to-FIP fitting needs to be tightened up to get rid of a small leak, you loosen the coupling and tighten the FIP as needed (it, and it's section of pipe will turn readily since the coupling is loose). Retighten the coupling and turn on the water.
Did you use thin white teflon, or the thicker pink or yellow type? Some threaded parts can easily take 2 to 3 wraps of quality teflon, sometimes more. It is good practice to also apply pipe sealant to the inside threads of the FIP prior to assembly. Plumber's putty is limited to drain rather than supply connections.
Sometimes threaded fittings fail (crack) because of QC issues, or because they're overtightened... Take a good look at that brass FIP, it may have a hairline crack that opens up when the fitting is tightened up.
Edited 12/18/2004 8:55 pm ET by Pierre1
Pierre has good suggestions. I think he means unions instead of couplings, though.
Pipe dope will work better than teflon tape. Tape works fine on well machined threads, but on general quality fittings dope works better. Plumbers putty is different than pipe dope and won't work on threads.
I assume you are not soldering the adapter fitting after you screw it on? You should solder a length of pipe to the fitting, then screw it on after it cools. Then sweat the other end, far enough away that you don't damage the teflon or dope with heat.
Also, your heat exchanger does have NPT tapered pipe threads and not straight threads or foreign (BSPT or metric, for example) threads?
My bad. You're right I should have said union - the fitting that allows a pipe to be disassembled and reassembled repeatedly with wrenches, while maintaining a watertight union (or dare I say joint). I always get unions and couplings mixed up, which is no big deal as I usually work by myself. Thanks Waynel
Sounds like Bob probably already has sweated on a coupling after he first re-tefloned the FIP. Good idea on keeping any new sweat-on fittings away from each other - 10" to 12" is usually enough if you have a powerful torch that can heat up the pipe and fitting quickly. If you can't help but be closer, or have a small torch, wrap a wet rag around the fitting you want to protect from melt-out.
you over tightened the adapters and stretched them...
replace the fittings... tape male threads.... dope female... reassemble...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
you using true adaptors or unions????
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
What others have said... use the heavier tape. 3 wraps. I use dope on the threads after taping. No soldering anywhere near the tape.
It shouldn't be too hard to get a seal... there's no real trick to it. More than two tries means you need to check the threads on your exchanger carefully.
I'm no plumber, but we've always used pipe dope for threaded copper fittings. My favoite is a brand called Slic-Tite, which has teflon mixed into the paste.
I've had better luck with this stuff than any sort of teflon tape.
Rigid thread sealant with teflon. And the thicker tape, the pink stuff.
Joe H