Tankless hot water heater related questions

Discussion in 'Tankless Water Heater Forum' started by monkey1, Jan 13, 2021.

  1. monkey1

    monkey1 New Member

    Jan 13, 2021
    I am replacing my tankless HWH soon. I have a few questions related to the new unit.
    1. My municipality provides 7 CW natural gas pressure for my residential line. If I buy a tankless HWH that is rated for 8 CW, will it run?
    2. How often do I REALLY need to descale the tankless HWH with white vinegar? I have a 2-person household.
    3. For how long do I run the descaling process? What will happen if I run the descaling process longer?
  2. breplum

    breplum Member

    Oct 2, 2004
    Plumbing and heating contractor
    San Francisco Bay Area
    Descaling frequency is important in relation to the mineral content of your water source.
    In our municipal supply here, we say that three or so years is ok between descaling.
    I have had three recent descale jobs who report the unit has never been descaled in 13 years.
    For those, I use commercial Whitlam descale fluid (diluted) and run it for an hour: Oh boy, what a load of crud came out.
    For a unit that is descaled on a proper yearly cycle, then 2 Gal. vinegar is great as long as the mineral content of the water was low enough. With vinegar on a regular descaling schedule, I run 1.25 hr. or longer.
    CLR is said to work well also.
    As to the inches water column question: Different mfrs products have different tolerances. Call mfr and ask.
    Navien NPE A series says it can handle 22ft of 1/2" gas pipe if directly from the meter.
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  4. fitter30

    fitter30 Well-Known Member

    Feb 2, 2020
    Retired service tech
    Peace valley missouri
  5. Dana

    Dana In the trades

    Jan 14, 2009
    That's true, but Navien is the extreme outlier.

    I don't know what magic they're working, but Navien is clearly doing something to make it easier for the average idiot to replace a plain old gas tank water heater with a tankless Navien without having to upgrade the gas plumbing. (Good for Navien!)

    But I suppose as with anything else, the more idiot-proof you make something, the more creative the idiots become...
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