Tankless Geek topic guide

    Groundwater Temperature and Tankless Flow

    Incoming-water temperature determines temperature rise and can change usable tankless flow more than the headline GPM suggests.

    Updated

    Direct answer

    Subtract inlet-water temperature from the desired outlet temperature. Compare that rise with the model's manufacturer flow chart. Recheck for winter conditions, when inlet temperatures may be lower.

    Use a winter design point

    Sizing for an annual average can leave a system short during the coldest period. Use a conservative local inlet temperature.

    Headline GPM is conditional

    Maximum GPM is not a universal output. The same unit supplies fewer gallons per minute at a larger temperature rise.

    Questions people ask

    Does climate zone alone give the inlet temperature?

    No. It is a useful starting point, but local water-system and seasonal conditions can differ. Measure or confirm locally when possible.