How any wraps on PTFE tape on a threaded drain off valve?

[king of pipes]

Locktite 55 for me brass into stainless ptfe is risky 16 wraps is my choice for rad tails . Kop

 

[Stigster]

Spot on, parallel threads aren't deigned to seal with PTFE tape.

Some radiator tails are taper thread though. On the parallel ones, do you recommend using a string type sealer? I suppose good old hemp and paste would work on a parallel thread well too?

 

[OffshoreGas]

Some radiator tails are taper thread though. On the parallel ones, do you recommend using a string type sealer? I suppose good old hemp and paste would work on a parallel thread well too?

Everything I’ve seen in in UK domestic plumbing and heating has been BSP parallel, some of the wiser guys in here may know better. I guess you have more NPT stuff on the US?

You can often get away with PTFE because the pressure is low. Your generally recommended to use an anaerobic thread sealant like Loctite 577. You can get an activator to speed up the cure time.