Aluminum Hydroxide; Aluminum Hydroxide - A.O. Smith GCV Series Service Handbook

SYMPTOMS "Crackling", "gurgling", or "popping" noises from new water heaters (installed less than
six months).
CAUSE In a few isolated parts of the United States where the water supply has a relatively
high pH (8+), water conditions will react with the aluminum anode to form excessive
amounts of aluminum hydroxide on the anode and in the bottom of the tank. Aluminum
hydroxide looks like "jelly beads" or a green, blue or gray gel like substance in the
heater drain or at faucet aerators.
THE FIX This procedure should only be performed by someone with abilities equal to a licensed
tradesman. Aluminum hydroxide can be removed by using one of the methods outlined.
If tank is new with no lime build-up to any degree:
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If tank is new with lime build-up to any degree:
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NOTES Since aluminum hydroxide is a product of a chemical reaction dependent on the water
condition, any treatment is not considered warranty related.
BULLETIN 14

ALUMINUM HYDROXIDE

Turn off the heater.
Remove the anode.
Flush the tank thoroughly with water.
Replace the aluminum anode (identifi able by smooth surface on plug) with
magnesium anode (identifi able by weld bead on plug).
Turn off the heater.
Drain the heater.
Remove the anode.
Add UN-LIME to the tank.
20-40 gallon models (use 3 gallons of UN-LIME)
41-65 gallon models (use 5 gallons of UN-LIME)
66-100 gallon models (use 7 gallons of UN-LIME)
Heat the UN-LIME to a temperature between 140°F to 160°F.
• GAS - Heat for 7 to 10 minutes.
Shut off the water heater.
Allow the heated UN-LIME to stand for up to 12 minutes.
Drain and fl ush the tank. Caution: UN-LIME will still be hot.
Replace the original aluminum anode with a magnesium anode.
Fill the system with water.
Turn heater fuel "ON".
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