Thermal Expansion Tank Tie-In in Houston, TX
Install a backflow preventer on a home's main line and you have created a closed system. When the water heater runs, heated water expands and has nowhere to go. Pressure climbs until the temperature and pressure relief valve on the heater, set at 150 psi, starts to weep.
A thermal expansion tank fixes that. It is a small steel tank with an air bladder, tied into the cold supply near the heater. The bladder absorbs the expansion.
The detail people skip is the air charge. The tank has to be pre-charged to match your static water pressure, checked with a tire gauge before it goes on. A tank left at the factory 40 psi on a 70 psi system does very little.
Sizing depends on heater capacity and water pressure. A 40 or 50 gallon heater usually takes a 2 gallon tank.
Grizzly Backflow & Plumbing connects Houston, TX homeowners with plumbers who tie in expansion tanks as part of backflow prevention work. Call (833) 990-5874.