If my gas line has this on the end of it, with a 1/2 flared connector on the left:

1/2" ballvalve

...and my flexible gas line from a kit is expecting 5/8 flares:

connector kit

...can I use this adapter that came with the kit -- which fits snugly but doesnt look like its expecting a flare on the 1/2" side -- to size up the connector on the valve?


In other words is it okay to put that top picture into the female side of the bottom picture? It's a perfect fit threadwise, but that flared tip makes me nervous.

So, I don't know if a flared connector has to go into a non-flared female side.

This whole flared adapter thing is confusing to me. It makes sense for flares to go into the copper pipe that has its ends rolled up, but it seems like I'm in "flared" mode here for no reason.

Actual photo:

enter image description here

Pipe in floor:

enter image description here

  • Does the female side of that adapter look like it has a flare to it? That's normally what those adapters are made for.
    – JPhi1618
    Dec 9, 2019 at 20:28
  • No it doesn't. To be fair it's not identical to the one pictured. Sorry I tried to find an exact product photo. Let me add an actual photo.
    – tmdesigned
    Dec 9, 2019 at 21:23
  • The new photo shows the flared tip right above the adapters female opening I want to put it in. It's a great fit and with putty I don't see how gas would care if the trip is flared or not, right?
    – tmdesigned
    Dec 9, 2019 at 21:32
  • Eeek! Definitely not. Flare fittings do not seal on the thread; they seal on the tapered face only. They should be assembled clean and dry. Spin the nut to finger tighten, then just another 1/4 turn or so with a wrench.
    – Greg Hill
    Dec 9, 2019 at 21:34
  • Will be following the advice not to do this. Thanks for keeping my family safe.
    – tmdesigned
    Dec 9, 2019 at 22:06

1 Answer 1


There are two common adapters that come with the yellow gas connector flex lines. The fittings on the flex line are normally flare fittings, so the adapters are to change the size of flare, or (I think more commonly) to adapt pipe threads to flare.

The flex lines that I have purchased recently came with an adapter that was flare on one end, and the other end had male and female threads for standard pipe. Your updated picture looks like this is the type in your kit. In my previous comment, I said the threads are different between flare and pipe, and they are somewhat, but you might be able to thread the connector all the way on and have it "feel right" if you're not sure what to look for.

Flare to flare fittings don't have the extra male threads (like your original stock image). The inside of the female threaded side will have an obvious cone shape for the flare to seal on.

So, to summarize based on the update image, I would say that the adapter you have is made to adapt standard pipe thread to a flare, and if you need to change the size of the flare, you need an additional adapter.

Bonus on thread types:

This site has some good info, but the basic thread sealing types are tapered threads, parallel threads and systems like flare fittings.

Steel pipe has tapered threads and the seal is created by the taper wedging the pipes together. Thread sealant/lubricant helps seal these because it helps get the threads tighter.

Things like shower heads and water hoses use parallel threads. The two fittings do not "get tighter" as you go, so sealing has to be done by a third party, which is normally a rubber washer. No sealant needed - the rubber does all the work.

Then, gas and hydraulic fittings are typically flare fittings. They use parallel threads as well, but the end of the fitting has some sealing... apparatus. The flared male and female sides are exactly matched or they use a malleable material (like soft pipe or a copper washer) so just small but firm tightening makes a gap-proof seal. Again, no sealant needed.

  • Thank you. That's helpful. To be honest all of this is because I am trying to add a shutoff valve. The pipe coming into the kitchen has a flared end as well. It's shutoff valve is on the other side of the floor in the basement.
    – tmdesigned
    Dec 9, 2019 at 21:46
  • So really what I want is to go from a 1/2" flare tip (gas line in floor) to a shutoff valve (of some type) to a 3/8" flare tip, at which point I can connect the flexible line.
    – tmdesigned
    Dec 9, 2019 at 21:48
  • Well, I think it's good to add an accessible shut off valve. I think it's worth going to get the right adapter. I added some info on thread types that you didn't explicitly ask for...
    – JPhi1618
    Dec 9, 2019 at 21:48
  • Does the pipe coming up not have a fitting you can remove? Is it male flare? Another pic might help.
    – JPhi1618
    Dec 9, 2019 at 21:49
  • Yes, I suppose it does have a piece that might come off. Pic added.
    – tmdesigned
    Dec 9, 2019 at 22:04

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