Estimate expansion tank size for a water heater or closed plumbing system. Calculate thermal expansion volume, required acceptance volume, recommended expansion tank capacity, system pressure range, precharge pressure, and expanded water volume.
Thermal expansion volume:
The calculator estimates how much water expands as it heats from the cold temperature to the hot temperature.
Acceptance volume:
The calculator applies a safety factor to the expanded water volume to estimate the tank’s needed acceptance volume.
Recommended tank size:
The calculator estimates total expansion tank capacity from acceptance volume, precharge pressure, and maximum allowed pressure.
Pressure range check:
The calculator compares a known tank size with the required expansion volume to help estimate whether it may be undersized.
An expansion tank size calculator helps estimate the tank capacity needed to absorb water expansion and reduce pressure spikes in a closed plumbing system.
It can help compare system volume, temperature rise, expansion volume, acceptance volume, precharge pressure, maximum pressure, and recommended tank size.
Your result shows estimated thermal expansion volume, required acceptance volume, and recommended expansion tank capacity. This is a planning estimate only. Final expansion tank sizing should use the tank manufacturer’s sizing chart and account for local plumbing code, water heater size, pressure reducing valves, check valves, relief valve rating, precharge setting, and system design.
An expansion tank is a small tank that absorbs expanded water volume when water heats up in a closed plumbing system.
An expansion tank is commonly used when a water heater is connected to a closed system with a check valve, backflow preventer, pressure reducing valve, or other device that prevents expanded water from moving back into the supply.
Expansion tank precharge is commonly set to match the cold static water pressure, but the tank manufacturer’s instructions should be followed.
No. This calculator gives a planning estimate. Final expansion tank sizing should be checked against manufacturer sizing charts and local plumbing code.