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Diagnose Gas Pressure Issues on a Tankless Water Heater

  • Transcript

    LESLIE: John in Pennsylvania needs some help with a tankless water heater. What’s going on?

    JOHN: I had a hot water heater that is tankless installed in my house …

    TOM: OK.

    JOHN: … professionally by a plumber. And it didn’t originally work properly because it has two settings inside for high-pressure natural gas or low-pressure natural gas. They had changed the setting and it seemed to work fine. In the summertime, in the warmer months, I have to reset it to get it to work and it seems to be a daily thing. But when it starts to get a little bit colder outside, it starts working better and I don’t normally have to reset it. I talked to a friend of mine who is a plumber and he said that there’s a good chance that the supplier of the natural gas will turn the pressure up on the natural gas because of the demand is higher so they need to meet the demand. Is there anything that I can do to fix the problem so that I don’t have to keep resetting it in the warmer months?

    TOM: It sounds very unusual. Have you contacted the manufacturer of the tankless unit to talk about this situation?

    JOHN: Yes, I did and they wanted me to buy an expensive meter that tells the pressure in the gas line at …

    LESLIE: How much is coming into you.

    JOHN: Yes. And that was like $130 meter and I was hoping that there would be a cheaper, easier way to find out what the problem would be.

    TOM: Well, we first need to know what the problem is and knowing the gas pressure is one thing. The other thing that I will tell you – and I don’t know if you’ve looked into this – is there’s a very, very common installation mistake with tankless water heaters and that is this: when you install a tanked water heater you typically use a ¾-inch gas line, but with a tankless water heater you need a larger gas line and the reason is because tankless water heaters, in order to work properly, need more gas in terms of volume. They use …

    LESLIE: Think of like a burst of it.

    TOM: They use it for a shorter period of time, so it doesn’t actually eat up more gas but it needs a larger flow of gas. And very commonly, plumbers put undersized gas pipes in which cause this exact problem. So I would look beyond the water heater to the size of the gas line. I’d document that and contact the manufacturer and find out if, in fact, this water heater was installed consistent with their recommendations in terms of the gas line.

    JOHN: OK.

    TOM: Because that could be your problem right there and then. And the other thing is, in terms of the gas pressure, I’d also contact the gas utility company and ask them if there’s adjustments to the pressure because it sounds like pretty good speculation on your friend’s part that the pressure could change. But knowing utilities like I do, I doubt that they’re going to be doing that because that could have all sorts of adverse effects.

    JOHN: Right. Thank you, guys. Thanks.

    TOM: You’re welcome. Thanks so much for calling us at 888-MONEY-PIT.

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