What is it about BRASS pipe that requires adding "wicking" or string to the threads to get it to SEAL properly.
I had to install a TP valve on a hot water heater for a friend of mine and used string along with the GRAY pipe dope of old.
Often on bigger fittings brass or not , 3 or 4 wraps of Teflon tape doesn't do the job and LEAKS. I had that problem on my furnace boiler at the pump connection. Add more teflon tape, still leaks. I took it off again and used gray dope - no more leaks for
20 years.I assemble galvanized and black pipe with teflon tape and no problems.
It seems only BRASS requires "wicking" and dope together.
WHY since threads are the same ?
TIA