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RESIDENTIAL GAS, NON POWER VENTED, WATER HEATER 
SERVICE HANDBOOK 
 
State Water Heater 
 
Technical Training Department 
© 2004 
 
Ashland city, TN 
9
Residential Gas - continued 
 
Water Flow:
 When a hot water faucet is opened, water pressure from the well tank or street 
main forces cold water into the water heater.  This pushes hot water out of the tank. 
Operation:
  A residential water heater is not a precise operating appliance. Because the water 
heater relies on the expansion and contraction of a metal rod, when the thermostat dial is set at 
an indicated setting (“▲” is recommended as a starting setting.  This is approximately 120 
degrees F.) The heater may shut off at 110 to 130
° F.  The heater will consistently shut off at 
this same temperature.  For this same reason, water temperature may drop 15 - 25
° F, around 
the temperature probe, before the main burner is activated.  Keep in mind that hot water in the 
upper part of the tank will probably be very near the “shut off” temperature of the control while 
incoming cold water drops the water temperature around the thermostat probe.  Also, short 
repeating heating cycles caused by small hot water uses can cause temperatures at the point of 
use to exceed the thermostat setting by up to 30° F. 
 
Setting  Approximate Temperature (°F)
Time To Produce 2
nd
 & 3
rd
 
Degree Burns on Adult Skin
Hot (▲) 
120° ± 10° 
5 Minutes 
130°  ± 10° 
30 Seconds 
140°  ± 10° 
5 Seconds 
150°  ± 10° 
1.5 Seconds 
Very Hot 
160°  ± 10° 
Under 1 Second