Teflon tape or string is not the best for plumbing. if you do use it then do one wrap. more might cause you to mis-thread or not tighten enough.
better is plumbing pipe dope.
though people do so little plumbing for themselves that buying dope isn’t practical. the tape will be useful then because it lasts and takes up little space.
Oh, I disagree. Teflon tape is great (never heard it called string). You need to wrap it the correct way on the threads. In the direction of that you would turn a nut on a bolt. And you need at least 4 very tight wraps. The stuff is magic.
One wrap? You’re using it wrong.
threaded plumbing depends on mechanical tightness to not leak.
4 layers of tape will restrict you from turning it as tight as you can.
Never in my experience. And I’ve done a lot, lot of plumbing. You’re not getting the tape tight enough. Four wraps (maybe 5) and work it down as you wind it on.
John, you’re doing it wrong.
The tape v dope is an ancient argument.
Either can be used on water lines.
My reference to teflon string is as packing string/cord.
I’m guessing we are looking at old steel pipes with washer and packing nuts - and packing nuts need some kind of packing - the old paper or new teflon cord/string.
If you don’t know about faucets which use packing, please do not assume I am talking about something you know. I’m not.
Teflon tape is used for sealing threaded joints. Teflon rope (or string if you wish) is used for packing. 2 different products for 2 different uses.
You can’t unclog them – replace them. (Eventually, when you have time – not in mid-winter.) Until then, treat them real gently – old pipe like this is fragile.
I had 1.5 inch galvanized drain pipe – when I replaced it, the scale & rust had clogged it so much there was a track about the size of a pencil weaving thru it that was the only clear space. Needed complete replacement.
I will be replacing the only remaining set of galvanized pipes this summer. Thinking about doing PEX. Sounds significantly easier than copper or plastic.
Check local building code re PEX.
I will never trust the stuff (especially if buried inside a wall), but I’m an old fart, so take my opinions accordingly.