I am getting ready to replace the pressuretrol of my oil-burning steam boiler, which provides heat and hot water. Should I use thread-seal tape (aka. Teflon tape, PTFE tape, tape dope, or plumber's tape) when attaching the new pressuretrol? If so, should I use the same kind of tape that I use for water pipes, or is there a special kind for use with steam pipes?

(The pressuretrol datasheet describes the connector as “1/4 inch female pipe thread.” I presume that is a synonym for national pipe thread taperered thread (NPT), so the threads themselves are providing the seal, and there is no gasket.)

  • 2
    Nit-picky wording detail: with NPT threads, the threads don't provide a seal, thus the need for thread sealing tape or compound. Sep 22, 2010 at 15:19

1 Answer 1


My favorite pipe thread sealer is RectorSeal #5. Here's a link. I see according to its datasheet that its rated for steam pipes. You might have to let it dry a little while before pressuring, but after that its good for 2600 psi.

  • It should be good for my measly 2 psi then. Sep 21, 2010 at 23:14
  • Why do you like it so much? Dec 10, 2010 at 19:40
  • My brother recommended it for use on gas pipes, and I just found it works well, stays soft enough to take apart and doesn't leak.
    – BrianK
    Dec 11, 2010 at 1:31

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