Water Heater Brochure

Hard water is everywhere. In fact, more than 85% of American homes have hard water which adversely affects
plumbing systems, including water piping, water fixtures and the water heating system.
What is hard water and hard water scale?
Water is classified as “hard” when it has a high mineral content, specifically magnesium and calcium (Ca2+ and
Mg2+ ions). Hard water is not considered a health risk and these minerals generally remain dissolved in the water.
However, problems arise when the minerals precipitate out of the water and leave behind a solid mineral buildup.
This buildup, called scale, reduces water flow through pipes and fixtures, reduces the energy efficiency of water
heating equipment and causes damage to the heat exchangers within tankless water heaters. Scale formation is
based on water hardness levels and the temperature, not on the material the scale is adhering to. For example,
hard water scale would form equally on a copper surface as it would on a stainless steel surface, given the same
hardness level and temperature of water.
What does hard water scale do to my water heater?
Scale is the number one threat to tankless water heaters where it reduces energy efficiency and damages the
heater. When hard water scale forms a layer coating on the inside wall of a tankless heat exchanger fin pipe, it acts
as a thermal insulator. This insulation effectively prevents a significant amount of heat from the burners to properly
transfer into the water within the piping. Because the heat is not transferring into the water, the heat exchanger
material retains this excess heat, eventually overheating and becoming damaged. Once scale forms, scale removal
maintenance can be performed, but the heater will never return to peak efficiency. Without scale removal, the heat
exchanger piping will eventually leak.
How is the hardness of water measured?
Water hardness is measured in either parts per million (ppm) or grains per gallon (gpg). Anything greater than 3
gpg is generally considered hard (United States Geological Survey).
ALASKA
HAWAII
PUERTO RICO
OVER 14 gpg
10 to 14 gpg
7 to 10 gpg
3 to 7 gpg
LESS than 3 gpg
Extremely Hard
Very Hard
Hard
Moderately hard
Slightly Hard
Classification
GPG
(Grains Per Gallon)
Slightly Hard Less than 3
Moderately hard 3 to 7
Hard 7 to 10
Very Hard 10 to 14
Extremely Hard Over 14
The U.S. Department of Interior and the Water Quality
Association
OVERCOMING HARD WATER SCALE
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