https://www.amerigas.com/about-propane/propane-tank-sizes https://www.amerigas.com/about-propane/propane-tank-sizes I've most commonly seen the 120 gallon size

https://www.amerigas.com/about-propane/propane-tank-sizes https://www.amerigas.com/about-propane/propane-tank-sizes I've most commonly seen the 120 gallon size at homes that use it for a water heater.