State Water Heaters STC-080 Service Handbook page 25

Standard residential gas water heaters
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RESIDENTIAL GAS, NON POWER VENTED, WATER HEATER
WHY WATER HEATER TANKS LEAK -
WATER CONDITIONS
WHAT
WHY
"Hard" Water
"Hard" water contains minerals.
As water is heated the minerals
separate from the water and
attach to hot surfaces within the
tank. In gas water heaters, these
minerals "insulate" the heat
transfer surfaces conducting heat
from the burner through to the
water. These surfaces become
hotter than if they were clean.
Hotter surfaces mean more
expansion and contraction of the
metal as the burner cycles on and
off. The metal or weld joints
crack.
Water stored at 160°F (72 °C)
Water
Temperature
may be twice as corrosive as
water stored at 140°F (60°C)
Usage
Each time the burner or elements
cycle on and off, a small amount
of metal expansion and
contraction take place. As
bending a piece of wire back and
forth will break the wire, this
expansion and contraction will
eventually crack tank joints or
welds.
State Water Heater
© 2004
SERVICE HANDBOOK
PREVENTION
"Flush" the sand from the tank every 6
months.
Delime the tank interior yearly.
Install a water softener in hard water
areas. These should be adjusted
according to manufacturer's
recommendations, typically for 5 grains
hardness.
Begin with a water heater setting of
120°F (49°C) and increase only as
necessary.
Purchasing a proper sized tank will
minimize burner or element operation
when only small quantities of hot water
are used.
24
Continued
Technical Training Department
Ashland city, TN

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