Licensed plumber safest bet for water tank

A reader writes in to say he bought a water heater and expansion tank and had them installed by someone who was not a licensed plumber.

The expansion tank was mounted horizontally — just hanging there, he said — on the water supply line above the heater.

A licensed plumber later added some nylon straps to support the tank and screwed the straps to a ceiling joist. No one ever checked the water pressure at the faucets, nor the limit on how much the expansion tank could hold.

The reader believes the tank is full and fears that if the straps gave way, it would flood his basement.

Thermal expansion is the term used to describe the expansion of water volume due to heating. All water heaters, regardless of heat source — gas, oil, electric, solar or indirect — can experience thermal expansion.

According to water-heater manufacturer Bradford White Corp., a thermalexpansion tank is a small, prepressurized tank with a compressible air cushion (a diaphragm) that is installed on the supply side (the coldwater inlet) of a water heater.

If thermal expansion of the water creates excess pressure within the heater, water is forced into the expansion tank, keeping pressure levels within the normal operating range of the heater.

As the pressure within the heater normalizes, the water within the expansion tank is forced back into the heater by the diaphragm, and the potentially harmful effects of the thermal expansion are eliminated.

My suggestion: Call the manufacturer of your equipment and ask questions. You’ll likely be told to call a licensed plumber.