Expansion Tank Sizing Calculator
Size thermal expansion tanks for hot water systems based on system volume, temperature range, and pressure settings.
Inputs
gallons
°F
°F
psi
psi
Results
Minimum Tank Size
-11.12 gallons
Pre-Charge Pressure
40 psi
Expansion Volume-7.43 gallons
Acceptance Factor0.5
How to Use This Calculator
- Enter the system water volume in gallons (sum the water heater tank plus all pipe and radiator volume).
- Set the cold fill temperature and maximum hot temperature (typically 40°F and 180°F).
- Enter the fill pressure (system pressure when cold) and the relief valve setting.
- Review Minimum Tank Size in gallons — select the next standard size up from your supplier.
- Set the Pre-Charge Pressure on the tank to match your fill pressure before installing.
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