RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK
A.O. Smith Water Products Company Technical Training Department
TECHNICAL BULLETIN
BULLETIN 13
SYMPTOMS
• Rumbling
• Crackling
• Popping
CAUSE
With the advent of high input and larger storage tanks in both commercial and
residential heaters, deliming has become a necessity of modern maintenance.
Lime (CaCO3), is the most notable factor when discussing water hardness.
Lime is present in every water system to some degree across the entire
United States. Since lime is inversely soluble [the more you heat, the more
lime comes out], higher usage, excessive hardness, and increased heating
surface can lead to a high incidence of “limed-up” heaters.
Symptoms often include a popping of water trapped under lime deposits or
the sizzling of water trapped next to elements, boiling it to steam.
THE FIX
Treatment of a “ limed-up“ heater is relatively simple. Since CaCO3 is a base,
the easiest way to dissolve it so it can be flushed from the heater is with an
acid. The most commonly used is phosphoric acid at a food-grade level.
Two common treatments marketed by A.O. Smith are Mag-Erad® and Un-
Lime®. Any well-stocked plumbing supply house should have a deliming
solution available.
The directions on the product should be followed explicitly.
NOTES
For additional information and instructions in deliming water heaters and
boilers, please refer to the following pamphlets available from A.O. Smith:
• Why? When & How: To Remove Water Scale from Tank Type Water
Heaters
• The Mag-Erad
®
Method of Cleaning Gas Fired Water Heaters
• Up-N-Down
™
Transfer Kit
• All About Deliming Coil Type Water Heaters
©2005 Ashland City, TN
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