I am building an addition, and I was hoping to run a new gas line into the addition directly from my propane tank to feed a new furnace and tankless water heater that will live in the addition. I am wondering if I can split the line after the First Stage regulator on the tank and have two Second Stage regulators on the house? Sorry for the poorly drawn picture, but hopefully it illustrates the point. If this is possible to do, what considerations do I need to take into account? And how would doing this split change the amount of pressure in each line?

My current line going into the house is 5/8" copper tubing.

tank with splitter

  • 1
    Seems plausible, but check with your gas supplier. The First stage regulator (and size of tank) needs to be big enough for both Second stages being fed off it. If that's true, the pressure to each should be the same. Depending on the size range of what you have, you might need an upgrade to make it work right.
    – Ecnerwal
    Commented Jan 19, 2021 at 3:51

1 Answer 1


Yes you can split after the first regulator. You may need to upsize the regulator as on demand water heaters are high usage devices if your current regulator is 75k btu snd you add a 50k water heater there is not enough for other devices but it can be done.

  • I'm curious why someone downvoted this one without providing a comment?
    – Bill
    Commented Jan 20, 2021 at 13:18
  • @bill it happens all the time lots of people that do not know what they are talking about the fact is you can split off of a first stage. For it to function properly the first stage needs to have a rating of the combined devices I have done this on several homes one had 2 propane heaters at opposite ends. another the furnace was on 1 end and the attached garage was on the other. I added heat in the garage. The advantage is the smaller line from the primary regulator to the secondary without pressure loss. This also improves the performance when 2 large devices kick in at the same time.
    – Ed Beal
    Commented Jan 20, 2021 at 14:19
  • "the first stage needs to have a rating of the combined devices" - does that mean if the first stage is 1,000,000 BTU, then the two second stages BTU ratings combined should sum to that (i.e. two 500,000 BTU regulators, or a 750,000 and 250,000 BTU combined)? Thanks!
    – Bill
    Commented Jan 20, 2021 at 16:07
  • 1
    Yes the first stage has to supply the total volume used at any 1 time. It is better for this to be larger than the combined 2 second stages for best performance. I have sized the 1st at 150% of the combined second stages because that just happened to be the next size larger.
    – Ed Beal
    Commented Jan 20, 2021 at 16:22

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