Tankless Water Heater gas line question

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by chetwynd, Jul 27, 2020.

  1. chetwynd

    chetwynd Member

    Joined:
    Jul 27, 2005
    Location:
    California
    Hi Guys,

    I've got some pretty solid plumbing experience but it's been a while since I've done much with it, and I'm running into a problem with the installation of a tankless water heater.

    First issue is that the flow meter on the remote control for it (Takagi, nat gas) doesn't show the flow that it should when we turn on the faucet. Maybe the flow sensor...but, that aside.

    We ultimately determined that the gas line we have running to it isn't big enough. Given the distance and BTUs, we need a 1" line going to it. See the attached image. As you can see, it starts at the meter as 3/4" (the only outlet from the meter is 3/4"), then goes into a long 1" pipe, then drops back down to 3/4".

    It basically needs to be 1" the entire way. BUT, it seems to me like unless the outlet on the meter is 1", then the initial 3/4" pipe the gas travels through would bottleneck there and make the 1" pipe beyond it basically useless...no? Meaning, if only 3/4" worth of gas capacity can feed the 1" pipe, doesn't that mean the 1" pipe isn't capable of moving as much as as if the meter outlet was 1"?

    See what I'm asking?

    Thank you.
     

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