Re: How much teflon tape to use?
Posted by dick on January 27, 19100 at 09:55:36:
In response to Re: How much teflon tape to use?
Wrong!! Pipe threads on regular iron pipe will almost never seal 100% without a filler of some kind. male and female threads will not match exactly and something must flow or distort to fill in the gaps. If the pipe could be torqued enough to make the steel distort and fill in the gap it would seal, however regular iron pipe will usualy burst the female thread before reaching that much torque. Brass pipe and fittings coated with grease, can frequently be torqued enough to make a seal. This is just because the brass material is softer. High strength steel fittings made for extreme pressures, can usualy be torqued enough to make at least a low pressure seal without tape or dope.

Two wraps of teflon tape "around the small end" of a correctly machined male pipe thread in reasonably good condition that can be properly torqued up is sufficient. if the teflon tape does not almost completly cover the engaged length of the male thread, make an extra wrap of tape to cover the extra thread or put a little grease on it. The nose of the thread is where you want it to seal.

I generaly use 3 wraps on most connections where I have reasonable access and can torque up the connection. When you get it tight, hold the maximum torque on the connection for 10-15 sec. This gives the teflon time to flow and seal better. When you are in an awkward spot and can't properly torque a connection, pipe dope sometimes works better because it requires less force to make it flow into the gaps.

Rusty, damaged, or poorly made threads all seriously decrease the reliability of a connection. Fix them or replace them. because normal plumbing pressures are so low, you can frequently get away with very poor connections, but sooner or later, they will bite you.

Teflon tape does not seem to vary in thickness a whole lot. Thicker tape would not conform and cling to the thread as well. It is naturaly white, but is easily colored. sometimes for identification, sometimes for consumer appeal.

: When a study was conducted on PVC joints that failed, it was found that it was because too much tape had been used and it cracked the fittings. Obviously that will not happen with metal pipe and fittings, but, normally no more than two layers are needed. However the important thing to remember is that the tape, or any other thread compound's, prime purpose is to reduce friction, so that the mating threads will make full contact. Filling any voids is a secondary function, so if the threads are old and rusty, there may be nothing that will prevent them from leaking.

: :
: : For a typical 1/2" international pipe standard coarse thread, how many wraps
: : of teflon tape are necessary to get a good seal? Does it matter if I'm dealing with
: : old rusty galvanized steel threads or crisp clean brass threads? Also, does it make a
: : difference which kind of tape I use? I just have the regular white stuff, but I have seen
: : other colors like blue and pink, are they of a different thickness or designed for different
: : types of joints?

: : Thanks in advance for any advice.

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