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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.
Chemical Hazard
• Product contains phosphoric acid.
• Keep out of reach of children.
• Use rubber or neoprene gloves.
Contains phosphoric acid. in c ase of external contact , ush
with cool water. if irritation persists, get medic al attention. if
swallowed, give 1 or 2 glasses of water or milk and call physician.
Get immediate medical attentio n for eyes. Keep out of reach of
children.
note: the use of ruBBer or neoprene gloVes is
recommended, especially if you haVe any open
sores or cuts to aVoid unnecessary irritation
or discomfort.
1. Turn off fuel and/or power supply to heater. Also, t urn
off power to any electrical device or equipment, which is
attached, or part of the system.
2. open hot water side of fauc et closest to h eater and allow
water to run until it is cool enough to handle safely.
3. Close co ld water inlet valve to heater.
4. Connec t hose to drain valve at bottom of heater and star t
draining heater into suitable oor drain area.
5. Remove relief valve while heater is draining. NoTe: Do not
replace relief valve until deliming is completed. Rel ief valve
opening will also act as a vent in case of possible co ntact
between the de limer and the anode rod(s), which may
produce ammable hydrogen-air mixtures.
6. if relief valve appears to be limed-up, place it in a clean glass
or plastic container adequate in size so that you can pour
enough uN•Lime® into the c ontainer to cover the valve and
allow space for foaming. When foaming stops, run fresh cool
water into the container and rinse the relief valve for a few
minutes.
7. if heater does not drain completely after a reasonable
length of tim e, turn of f the main water supply valve to stop
water from entering t he tank due to a by-pass problem or
defective cold water inlet valve. Also, check for clogged drain
valve opening. Heater must be c ompletely dr ained before
introducing uN•Lime.
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 har mful fumes which are associated
with other products.
uN•Lime may be obtained from your dealer, distributor or A. o.
Smith Product Servic e Division. order Part Number 9005 416105,
1 gallon, packed 4 gallon s per case or Par t Number 9005417105,
5 gallon container.
NoTe: un•Lime is not available for use in Canada.
Hydrochloric base acids are not recommended for us e on glass
lined tanks.
observe handling instructions on label of pro duct 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 o pen to maintain pressure
in tank.
2. A cleanout opening is provided for perio dic 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 f rom 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 c are not to damage
the glass lining.
7. inspect cleanout plate gasket, i f new gasket is required,
replace with part no. 900409 9215.
8. install c leanout plate. Be sure to draw plate up tight by
tightening screws securely.
9. Replace ou ter 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 heate r using the flo-Jug method, rst
prepare the heater for deliming.