Expansion tanks are now required to be installed on all water heaters in a house. Their purpose is to protect the water heater from exploding if the pressure within the tank becomes to much. Those of you who know what a T&P Valve (temperature and pressure) is may be asking yourself... "Isn't that the function of the T&P Valve?" And you would be absolutely right. However, over time T&P valves can become frozen and not function as intended (discharging water from the tank if the temperature of the water exceeds 212 degrees or the internal pressure exceeds 150 psi). Expansion tanks are now required as a back up to the T&P Valve. Note that because the water heater is a closed system a PRV (pressure regulator valve) will be required to be installed at the water meter box to provide additional control. In fact in homes with more than one water heater, each unit will require an Expansion Tank because each water heater unit is a closed system.
Expansion tanks are necessary because as water heats and becomes hotter... the water expands creating more pressure within the water heater tank. The pressure regulator valve allows the home owner to adjust and control the PSI (pounds per square inch) of the water entering into the home. In San Antonio the water pressure should be between 40psi to 80psi. Anything over 80psi begins to put increased pressure on the soldered joints. Every home owner loves great water pressure but too much water pressure can lead to pipes bursting. When this happens you had better know where the main cutoff valve is and hope that you are home to use it. Otherwise interior flooding can create unbelievable damage. Home ownership is an ever expanding source of expense and headaches which is why it pays to know as much as you can about your home.
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