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MAINTENANCE SCHEDULE
Component Operation Interval Required
Tank Flushing Periodically
Un•Lime
®
Elements Lime Scale As needed delimer &
Removal element
gaskets, Part
Anode Inspect As needed
Tank flushing should be performed in accordance with the above
schedule. Tank sediment removal and element lime scale removal
must be performed as needed as determined by periodic
inspection. Following are the instructions for performing
recommended maintenance.
FLUSHING
The water heater drain valve should be opened periodically to
help prevent sediment buildup on the tank bottom.
1. Turn off the electrical disconnect switch.
2. Attach hose to outlet opening of drain valve and direct end to
drain.
• Open the drain valve by turning the hand wheel to the left
(counterclockwise). Allow water to flow until it runs clean.
• If water does not flow from opened drain valve, follow
instructions for sediment removal.
3. When finished flushing:
• Close heater drain valve and remove hose.
• Turn on electricity.
SEDIMENT REMOVAL
Water borne impurities consist of fine particles of soil and sand
which settle out and form a layer of sediment on the bottom of the
tank. In time, if not removed, the level of sediment might reach
the heating elements and cause their failure.
For convenience, sediment removal and element lime scale
removal should be performed at the same time as follows.
LIME SCALE REMOVAL
Lime scale accumulations on the heating elements is a normal
condition, common to all immersion type elements. Factors which
affect the amounts of this formation are:
1. Amount of hot water used. As the volume of water heated
increases, more scale results.
2. Water temperature. As the temperature of the water is
increased, more scale is deposited on the elements.
3. Characteristics of water supply.
Regardless of water treatment, the elements should be
examined regularly.
Lime scale accumulations may cause noises to occur during
operation.
It is recommended that a heating element be removed periodically
for examination. If it is scaled, all of the elements should be
removed and cleaned. If the tank bottom has an accumulation of
sediment it should be cleaned.
Lime scale should be removed by dissolving the accumulation in
UN•LIME
®
delimer. UN•LIME is a non-muriatic delimer, available
from Product Service Division, A.O. Smith Water Heater Parts
Fulfillment, 125 Southeast Parkway, Franklin, TN 37068. Do not
use muriatic or hydrochloric acid base deliming solutions to
remove lime scale from the elements.
Replacement gaskets, part no. 9000308, should be available at
this time.
1. Turn off electrical disconnect switch.
2. Drain the heater following DRAINING instructions.
3. Open front panel.
4. Disconnect the element wiring. Try not to disturb the wiring
unnecessarily and reconnection will be easier.
5. Unscrew each element.
6. Remove the elements and gaskets from the openings.
• Use a twisting, pulling action to remove elements scaled
beyond the size of the tank openings.
• Brush loose scale from elements.
7. Lime scale removal:
• Place limed ends of heating elements into UN•LIME delimer
and allow scale to dissolve. Do not permit delimeror water
to contact heating element electrical terminals.
Other scale removal:
• Silicates, sulfates, and aluminates must be removed by
scraping or other mechanical means. Lime scale dissolvents
will not remove these types of scale which are occasionally
encountered.
8. Flush cleaned ends of elements with water when deliming or
cleaning is completed.
9. Remove sediment and scale from the tank bottom through
the access provided by the element openings or drain valve
opening.
• The cold water inlet valve and drain valve may be opened to
aid the cleanout process.
10. Clean remaining gasket material from tank and element
flanges. Do not reuse original element gaskets.
11. Put new gaskets on each element and install into tank
openings.
• Uniformly tighten element bolts. Torque to approximately 32
ft./lbs.