MIL-HDBK-1165
schematic of the inner components of a typical natural gas heater
is shown in Figure 18 for reference.
5.4.2.2
Operation and Maintenance Procedures. Proper
maintenance of existing water heaters is important because of two
major problems that affect them: (1) scale or sediment buildup
and (2) corrosion. These problems, if left unchecked, can
decrease the efficiency of a water heater or even destroy it.
Scale and sediment form in hard water environments, corrosion
results when soft water is used (to control hard water deposits).
The hotter the water, the more accelerated is the scale and
corrosion formation, due to the increased formation of corrosive
gasses like oxygen and lime deposition. Scale, sediment
accumulation, and corrosion decrease the water heater's ability
to transfer heat to the water, causing it to consume more energy.
Most water heaters employ a "sacrificial" anode that is put in
the tank to preferentially corrode when galvanically coupled to
the tank. New water heaters also are usually lined with
fiberglass or plastic to protect metal parts from corrosion.
Even with these internal corrosion inhibitors, the following
maintenance procedures should be performed to keep the water
heater at peak performance:
a) Periodically (annually or as needed) drain the
water heater and flush out any sediments.
b)
Inspect the anode and replace if completely
corroded.
5.4.2.3
Retrofits. There are a number of retrofits that can be
performed on a water heater to save heat energy and consequently
conserve water:
a) For new construction, locate the end-use devices
closer to the water heater, and choose a heated area for the
water heater location.
b) Install an auto-setback control - it adjusts the
aquastat setpoint to the required level right before a time of
peak demand, then lowers it during periods of low demand.
c) Install a premixed water distribution system - a
system that is installed between the water heater and the end-use
devices. It allows the user to control the water temperature and
flow rate precisely by mixing hot and cold water in a central
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