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