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PREVENTIVE MAINTENANCE
RECOMMENDED PROCEDURE FOR PERIODIC
REMOVAL OF LIME DEPOSITS FROM TANK TYPE
COMMERCIAL WATER HEATERS
The amount of calcium carbonate (lime) released from water is in
direct proportion to water temperature and usage, see chart. The
higher the water temperature or water usage, the more lime deposits
are dropped out of the water. This is the lime scale which forms in
pipes, heaters and on cooking utensils.
Lime accumulation not only reduces the life of the equipment but
also reduces efficiency of the heater and increases fuel
consumption.
The usage of water softening equipment greatly reduces the
hardness of the water. However, this equipment does not always
remove all of the hardness (lime). For this reason it is recommended
that a regular schedule for deliming be maintained.
The time between cleaning will vary from weeks to months
depending upon water conditions and usage.
Refer to A. O. Smith booklet, Form No. 4800, entitled "Why? When
and How" for detailed description on tank inspection and cleanout.
UN•LIME
®
and the booklet may be obtained through your
A. O. Smith dealer or distributor.
DELIMING SOLVENTS
A. O. Smith recommends the use of UN•LIME for deliming. UN•LIME
is a patented food grade acid which is safe to handle and does not
create the harmful fumes which are associated with other products.
UN•LIME may be obtained from your dealer, distributor or the
A. O. Smith Product Service Division. Order part no. 4763 (1 gal),
packed 4 gallons per case or part no. 4813 (5 gallon container).
Hydrochloric base acids are not recommended for use on glass-
lined tanks.
Observe handling instructions on label of product being used.
CAUTION
TANK CLEANOUT PROCEDURE
The following practices will ensure longer life and enable the unit to
operate at its designed efficiency:
1. Once a month the heater should be flushed. Open the drain
valve and allow two gallons of water to drain from the heater.
Inlet water valve should remain open to maintain pressure in
tank.
2. A cleanout opening is provided for periodic cleaning of the tank.
Gas must be shut off and heater drained before opening
cleanout.
To clean heater through cleanout opening, proceed as follows:
1. Drain heater.
2. Remove outer cover plate from lower side of heater jacket.
3. Remove six (6) hex head screws securing tank cleanout plate
and remove plate.
4. Remove lime, scale, or sediment using care not to damage the
glass lining.
5. Inspect cleanout plate gasket, if new gasket is required, see
replacement parts list for item number.
6. Install cleanout plate. Be sure to draw plate up tight by tightening
screws securely.
7. Replace outer jacket cover plate.
In some water areas the sediment might not be removed by this
method and may result in the water heater making rumbling or
boiling noises. To dissolve and remove these more stubborn
mineral deposits, A. O. Smith UN•LIME Professional Delimer should
be used.
15
FIGURE 9
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