What is the minimum water flow required to operate a Rinnai Tankless Water Heater?
Rinnai tankless gas water heaters need a demand of at least 0.4 to 0.6 gallons per minute of water flow through the hot side to ignite and 0.26 gallons per minute to stay in operation. If the flow rate falls below these levels, the energy-efficient Rinnai unit will turn off because it senses that hot water isn’t needed.
There are several possible solutions to minimum flow rate issues. You can try lowering the temperature on the unit to avoid cutting in too much cold water; cleaning the inlet water filter on the cold water inlet of the unit to remove sediment buildup that can decrease flow; cleaning or removing the aerators from showerheads or fixtures; or replacing low-flow showerheads or fixtures. If you believe that none of these are the issue, contact your original installer or plumber to service the unit.