I am trying to hook up a gas dryer. The gas line has a flare fitting 1/2 in. that goes into a 1/2 in. x 3/8 in. coupling/reducer (in order to fit into a 3/8 in. gas connector, as suggested by help from Home Depot) and then into an excess flow valve, which then goes into a 3/8 in. gas connector (and then the dryer) Should I put Teflon Tape or Sealant on any of these connections?enter image description here

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    Thread sealant must be used when the threads themselves make the seal, as in normal pipe threads. But if the function of the threads is simply to hold two sealing surfaces together, then the threads should not be sealed. Your valve is meant to have a flexible gas tube attached to it which would not require thread sealant, but it is not clear from your picture if the brass adapter you show would require sealant or not. What is the exact description of that adapter? Does it have a sealing face inside the female end that would mate with the male sealing face on the valve? Or is it just NPT (FIP)? Mar 4, 2018 at 11:13
  • It looks to me like you could get a flexible supply tube that would connect directly to the valve without any adapters. The valves on my gas supply have female NPT threads (FIP) and require an adapter with male NPT (MIP) on one end and male "nozzle" which the flexible supply tube connects to. Mar 4, 2018 at 12:35
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    Hello, and welcome to Stack Exchange. Trial-and-error isn't a great approach when you're dealing with gas appliances, and no advice we could give you could guarantee you won't get blown up. Be careful! Mar 4, 2018 at 13:57

2 Answers 2


You will use

Pipe sealant ( pipe dope ) or yellow pipe tape ONLY on the connection going into the female part of the excess flow valve.

Not on flare compression fittings.

video from brasscraft, maker of the excess flow valve.

This video will show all you need to know.

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Looks like you have to connect the gas flex directly to the valve and no other other fitting in-between since the valve itself has already the flare male and the hose is flare female, you can't put either of those fittings because they're taperd and not flare the question is only if the valve and hose are the same size if not then you need a flare reducer or another size hose, and no sealant should be applied on treads of a flare connection since the seal is achieved by the flare being tight and not through the treads.

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