Brochure

Hard Water and Tankless Heaters
Hard water can adversely affect plumbing systems, from water piping to water fixtures and even down to the water heating system.
For piping and fixtures, hard water can create more pressure loss and reduce water flow. For water heaters, it can even reduce energy
efficiency and damage the heater. This is especially true for tankless water heaters and it is important to understand what hard water is,
what hard water does, and how to protect your tankless water heater from possible damage caused by hard water.
What is hard water and hard water scale?
Very simply, hard water is defined as water that has a high mineral content, specifically in magnesium and calcium (Ca
2+
and Mg
2+
ions).
Hard water is not considered a health risk and these minerals generally remain dissolved in the water. However, the problems arise when
the minerals precipitate out of the water and leave behind a solid mineral buildup. This buildup is called hard water scale, and it is this
scale that reduces water flow through pipes and fixtures, reduces the energy efficiency of water heating equipment and, at worst, causes
irreversible damage to the heat exchangers within tankless water heaters. It is important to note that the likelihood of scale formation
is only based on the hardness levels of the water and the temperature of the water, 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?
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 is forced to retain this excess heat, eventually
overheating and becoming damaged. Once the material has degraded enough,
the heat exchanger piping eventually gives way and water leakage occurs.
Picture shows a clean HX
with treatment.
Scale buildup from
untreated water.
With Treatment
Without Treatment
Copper Fin
Copper Fin
Burner
Full heat transfer
Limited heat transfer
Copper Tube
Copper Tube
Full water flow and heat transfer
Limited water flow
CLASSIFICATION
mg/L OR PPM (PARTS
PER MILLION)
GPG (GRAINS
PER GALLON)
Soft
0 - 17 0 - 1
Slightly Hard
17 - 60 1 - 3.5
Moderately Hard
61 - 120 3.5 - 7.0
Hard
121 - 180 7.0 - 10.5
Very Hard
180 and above 10.5 and above
How is the hardness of
water measured?
Water hardness is measured in either parts per million
(ppm) or grains per gallon (gpg). Anything that measures
above 3 gpg is generally considered hard (United States
Geological Survey) and it is advised at this point to look
into water treatment. The U.S. Department of Interior
and the Water Quality Association have classified water
hardness under several levels:
65