The flow rate of a tankless water heater, measured in Gallons Per Minute (GPM), indicates how much hot water the unit can provide at a given time.
Create an inventory of all the fixtures that require hot water, e.g., showers, sinks, and other appliances.
Manufacturers often provide this information however, you can also use a flow rate measuring device.
– Showerhead: 2.5 GPM – Kitchen Sink: 1.5 GPM – Bathroom Sink: 1.2 GPM – Dishwasher: 1.5-2.5 GPM – Washing Machine: 2.0-2.5 GPM
Account for the combined GPM when multiple fixtures are used simultaneously. Add their flow rates together.
Add a safety margin to ensure your heater can handle peak demand. A 20-30% margin is recommended.
(1) If your shower has a flow rate of 2.5 GPM and your sink has 1.5 GPM, the total GPM requirement is 4.0 GPM.
(2) A 30% safety margin for a 4.0 GPM means that your tankless water heater capacity should be 5.2 GPM.
Look for a tankless water heater that can provide the best flow rate following the total GPM requirements with a safety margin.
Call for a licensed technician to install your tankless water heater. Proper installation, maintenance, and repair are key to keep your unit running.