Start Up Conditions
THERMAL EXPANSION
Water supply systems may, because of such events as high line pressure, frequent cut-offs, the effects of water hammer among others, have installed devices such as pressure reducing valves, check valves, back flow preventers, etc...to control these types of problems. When these devices are not equipped with an internal by-pass, and no other measures are taken, the devices cause the water system to be closed. As water is heated, it expands (thermal expansion) and closed systems do not allow for the expansion of heated water.
The water within the water heater tank expands as it is heated and increases the pressure of the water system. If the relieving point of the water heater’s temperature-pressure relief valve is reached, the valve will relieve the excess pressure. The temperature-pressure relief valve is not intended for the constant relief of thermal expansion. This is an unacceptable condition and must be corrected.
It is recommended that any devices installed which could create a closed system have a by-pass and/or the system have an expansion tank to relieve the pressure built by thermal expansion in the water system. Thermal expansion tanks are available from Sears stores and through the Sears Service Centers. Contact the local plumbing inspector, water supplier and/or the Sears Service Center for assistance in controlling these situations.
Thermal Expansion Tank Specifications
| Tank | Dimensions | Pipe |
Model | Capacity | in Inches | | Fitting |
Number | In Gallons | Diameter | | Length | On Tank |
153.331020 | 2 | 8 (203 mm) | 12-3/4 (323 mm) | 3/4” Male |
Expansion Tank Sizing Chart
Expansion | Inlet* | Water Heater Capacity (Gallons) |
Tank | Water | | | | |
Capacity | Pressure | 6 | 10 | 20 | 30 |
Needed | 40-80 psi | 2 | 2 | 2 | 2 |
*Highest recorded inlet water pressure in a 24 hour period or regulated water pressure.
NOTE: Expansion tanks are pre-charged with a 40 psi air charge. If the inlet water pressure is higher than 40 psi, the expansion tank’s air pressure must be adjusted to match that pressure, but must not be higher than 80 psi.
FIGURE 29.
Strange Sounds
Possible noises due to expansion and contraction of some metal parts during periods of heat-up and cool-down do not represent harmful or dangerous conditions.
Operational Conditions
SMELLY WATER
In each glass-lined water heater there is installed one anode rod (see parts section) for corrosion protection of the tank. Certain water conditions will cause a reaction between this rod and the water. The most common complaint associated with the anode rod is one of a “rotten egg smell”. This odor is derived from hydrogen sulfide gas dissolved in the water. The smell is the result of four factors which must all be present for the odor to develop:
A.A concentration of sulfate in the supply water.
B.Little or no dissolved oxygen in the water.
C.A sulfate reducing bacteria within the water heater. (This harmless bacteria is non-toxic to humans.)
D.An excess of active hydrogen in the tank. This is caused by corrosion protective action of the anode.
