Quote:
Originally Posted by Tom52
Over 40 years I have owned 4 houses previous to moving to TV. None of the hot water systems had an expansion tank installed. I never noticed any variations in water pressure or premature failure of the components. I would think if there was excess pressure build up sufficient to cause damage it would pop the pressure relief valve on the hot water heater. A Google search didn't convince me as to the need of an expansion tank.
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Here are some reasons:
1. The expansion tank is required by code
2. A normal water pressure is about 60 psi, and the expansion tank is designed to maintain that pressure level.
3. The relief valve is a safety device that will only trip if the pressure exceeds 150 psi, which is way higher than a normal pressure. These valves often get clogged with calcium deposits and may not function properly over time.
4. Older houses are less likely to experience excessive water pressure because they may have small leaks in the system or may not have a good backflow preventer.
5. If you use all the hot water in the tank, and then shut off every fixture in the house, the tank will be full of cold water which will heat up. As it heats, the water pressure will increase due to expansion which can result in a dangerous pressure level. The expansion tank is designed to allow for the water to expand and keep the pressure down.