In the water supply system in a home or business, one of two types of systems
exist. The first system is called an "open loop system" where water can expand
freely when the water heater is operating. Simply put, when water is heated, it
expands and with the "open loop system", this can be done without any damage to
the water heater.
The other system that exists is called a "closed loop
system". This type of system is created when a water softener, check valve or
pressure reducing valve is introduced into the plumbing system. In a "closed
loop system", the previously mentioned devices restrict the expanding water from
the water heater. The end result of this thermal expansion is the stressing of
the water heater tank to cause it to either bulge at the top or the bottom of
the tank or to stress the seams of the steel tank to eventually cause it to leak
which then necessitates replacement of the water heater.
Another problem
that can occur with a "closed loop system" is the discharge of water from the
temperature and pressure relief valve that is located either on the side or top
of the water heater. The relief valve is designed to dump water when there is
excessive temperature or pressure in the water heater tank. If this should ever
occur, shut the water off to the water heater, turn off the gas or electricity
to the water heater and call a licensed plumber to make the necessary repairs.
NEVER REMOVE THE RELIEF VALVE AND INSTALL A PLUG. DOING
SO WILL LITERALLY CAUSE THE WATER HEATER TANK TO EXPLODE.
The thermal
expansion tank has a bladder in it that will expand and contract in conjunction
with the operation of the water heater when a "closed loop system" exists.
Although other devices are available to control thermal expansion, thermal
expansion tanks are the preferred method by Heffner and Associates.
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