Gallons per minute (GPM) measures how much water flows through a system in one minute. It is used to size plumbing, hydronic HVAC, and irrigation systems, and to verify that fixtures and equipment deliver the right flow for comfort and performance. Managing GPM helps balance water conservation with reliable hot water delivery and system efficiency.
/ˈɡælənz pər ˈmɪnɪt/ (GPM)
Gallons per minute (GPM) measures how much water flows through a system in one minute. It is used to size plumbing, hydronic HVAC, and irrigation systems, and to verify that fixtures and equipment deliver the right flow for comfort and performance. Managing GPM helps balance water conservation with reliable hot water delivery and system efficiency.
Why does GPM matter?
It determines how much water a system can deliver, affecting comfort, efficiency, and equipment sizing.
Source: The Cooling Company
GPM helps size fixtures, piping, and hydronic systems.
A homeowner chooses low-flow showerheads rated in GPM to cut water use while a hydronic system designer sizes circulator flow based on required GPM.
Check fixture flow ratings and look for leaks; small GPM reductions can cut water and energy costs without sacrificing comfort.
“Check fixture flow ratings and look for leaks; small GPM reductions can cut water and energy costs without sacrificing comfort.”
Modern fixtures are designed to provide strong performance at much lower GPM rates than older models.
Is higher GPM always better?
No. Excessive flow can waste water and energy, while too little can reduce comfort.
How do I find a fixture's GPM?
Check the product label or specification sheet for the flow rating.
Does GPM affect tankless water heaters?
Yes. Tankless units require a minimum flow rate to activate and maintain temperature.
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