Do I need a thermal expansion tank for my
water heater?
| Thermal expansion tanks provide a safe place for
expanded water to go. Most water meters are
installed with backflow prevention devices that
can create a closed system. Pipes in your home
may burst unless there is someplace for this
expanded water to go. |
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| About Water Heater Expansion Tanks |
 Virtually, every
modern plumbing code requires the installation
of an expansion tank on hot water heater
installations. The reason is simple. Water
expands when heated. This extra volume of water
needs to go somewhere. Before the widespread
usage of backflow preventers, check valves and
pressure reducing valves, this expanded water
simply pushed the cold water back into the city
water main. If your house has one of the above
mentioned devices, you could have problems.
These devices prohibit the flow of water from
your house back into the public water system.
Without
an expansion tank, the expanding water can cause
your hot water heater to possibly fail because
of the increased pressure. This pressure can
cause serious life threatening problems as well,
if you heat your water with natural gas or
propane. The water heater tank can collapse
around the internal flue and cause carbon
monoxide to enter your home. It is serious
business.
Expansion tanks are really simple devices. They
contain compressed air and a special rubber
bladder. When your hot water heater turns on,
the water within your piping system begins to
expand. This expanding water enters the
expansion tank. Eventually, hot water is drawn
from the system thru a faucet and the expansion
tank releases the extra water into the piping
system.
 Expansion
tanks come in various sizes. The size you need
depends upon two very important variables. You
need to know the capacity in gallons of your
water heater and the water pressure of your
house piping system. The capacity of your hot
water heater is stamped on a label or a plate on
the side of your hot water heater.
Water pressures within municipal water systems
vary widely. Here in Cincinnati, water main
pressures vary from 50 pounds per square inch (PSI)
to over 200 PSI within a distance of a mile!
This same thing may be true in your city. People
with cisterns or wells control their own system
pressure thru the use of electric pumps.
It is easy to determine your incoming water
pressure. Many plumbing supply houses sell a
little gauge that attaches to any faucet which
has garden hose threads. Or if you like, you can
call your local water department. They will
possibly send a technician to your house. This
person has very accurate gauges which will do
the same thing.
Once you have this information, visit a local
plumbing supply house that sells these tanks.
They will be able to provide you with the proper
sized tank to suit your needs.
Be sure to follow the directions that are
packaged with the expansion tank. It only takes
a few moments to read them. This will insure
that your tank will function properly.
If you install a pressure reducing valve to
control water hammer, be sure to buy one with a
bypass feature. Without this, your water heater
will begin to malfunction. You will see water
dribble out of the pressure/temperature safety
valve without a doubt.
The reason lies in the fact that heated water
expands. Without a pressure reducing valve, this
expanded water can easily go right back outside
to the water main. Low quality or malfunctioning
pressure reducing valves block this backwards
flow of expanding water. |
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