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NOTE: Un•Lime is not available for use in Canada.
Hydrochloric base acids are not recommended for use on glass
lined tanks.
Observe handling instructions on label of product being used.
TANK CLEANOUT PROCEDURE
The following practices will ensure longer life and enable the unit
to operate at its designed efciency:
1. Once a month the heater should be ushed. 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:
3. Drain heater.
4. Remove outer cover plate from lower side of heater jacket.
5. Remove six (6) hex head screws securing tank cleanout plate
and remove plate.
6. Remove lime, scale, or sediment using care not to damage
the glass lining.
7. Inspect cleanout plate gasket, if new gasket is required,
replace with part no. 9004099215.
8. Install cleanout plate. Be sure to draw plate up tight by
tightening screws securely.
9. 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.
DELIMING USING FLO-JUG METHOD
UN•LIME in the 5 gallon size is recommended for deliming of all
models. Contact your local A.O. Smith dealer, distributor or, A.O.
Smith Water Products Company:
Telephone: (800) 433-2545
Fax: (800) 433-2515
Website: www.hotwater.com/parts
Prepare the Water Heater
To delime the water heater using the Flo-Jug method, rst
prepare the heater for deliming.
Explosion Hazard
Flammable hydrogen gases
may be present.
Keep all ignition sources away
from faucet when turning on
hot water.
Do not smoke or have open ame or sparks in vicinity of heater.
Do not mix UN•LIME with other chemicals. Do not allow contact
with magnesium, aluminum or galvanized metals.
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 equipment but also
reduces efciency 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.
The depth of lime buildup should be measured periodically.
Heaters equipped with cleanouts will have about 2" of lime
buildup when the level of lime has reached the bottom of the
cleanout opening. A schedule for deliming should then be set
up,based on the amount of time it would take for a 1" buildup
of lime. It is recommended that the water heater initially be
inspected after 6 months.
Example 1:
The initial inspection after 6 months shows 1/2" of lime accumulation.
Therefore, the heater should be delimed once a year.
Example 2:
The initial inspection after 6 months shows 2" of lime accumulation.
Therefore, the heater should be delimed every 3 months.
FIGURE 27.
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 A. O.
Smith Product Service Division. Order Part Number 9005416105,
1 gallon, packed 4 gallons per case or Part Number 9005417105,
5 gallon container.