Teflon tape, pipe dope, or both?

[hlweyl]

Hi all,
I've been searching but unable to find an answer. I connected a new outside hose-bib yesterday. All the joints I soldered are fine, but where the brass bib threads to the copper it is leaking. I only used pipe dope.

Should I have used teflon tape instead, or both? Can someone who knows, please post a general guide on which compound to use with threaded pvc-pvc, pvc-copper, etc?

Thanks in advance!
Dave

 

[hj]

joint

There is no general rule. I always use dope, others prefer tape, and the insecure among us use both. The real problem is either it is not tight enough, or you soldered the fitting after it was assembled.

 

[Sponsor]

 

[hlweyl]

I soldered the copper fitting on, then applied the dope, then threaded the hose bib on. I felt like it was tight enough and any farther and I would have stripped the threads, which I've been known to do.

After I installed the bib, I had one last fitting to solder and the copper coupler about 12" away. Do you think the heat at that distance could have messed up the pipe dope?

 

[CaptWally]

Hj is correct- there is no general rule, but some guidelines that only come from experience. Some use pipe dope, some use teflon tape, some use both...

Well I use one, the other, or both depending on the composition of the threads. A softer material threading into a harder material (ie, PVC threading into a galvanized, or vice-versa as in copper threading into brass) requires less thread sealant as the softer material will conform to the harder material. Threading copper to copper or steel to steel is less forgiving, and sometimes I will use both tape and dope in those situations, sometimes not. It just depends on the "feel" of the connection.

I can not stress this enough, however: Absolutely use a high quality pipe dope. Most Home centers or hardware stores do not sell a decent pipe dope. The brands I recommend are "Jo-Mar" and EZ Thread Seal. They are not like the white teflon based products that are prevalent in most retail outlets. Go to a wholesale supply house if you have to.