Brochure

47
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
Tankless Model H3M KJr2/U H3J K4/U D2/U H3S H3 M50
Input (BTU/h) 120000 140000 160000 190000 199000 180000 199000 380000
Output (BTU/h) 111600 114800 152000 155800 163180 171000 189050 304000
85 6.40 6.56 6.60 8.00 9.32 8.00 10.00 14.50
80 5.60 5.74 6.60 7.79 8.16 8.00 9.45 14.50
75 5.00 5.10 6.60 6.92 7.25 7.60 8.40 13.51
70 4.50 4.59 6.08 6.23 6.53 6.84 7.56 12.16
65 4.10 4.17 5.53 5.67 5.93 6.22 6.87 11.05
60 3.70 3.83 5.07 5.19 5.44 5.70 6.30 10.13
55 3.40 3.53 4.68 4.79 5.02 5.26 5.82 9.35
50 3.20 3.28 4.34 4.45 4.66 4.89 5.40 8.69
45 3.00 3.06 4.05 4.15 4.35 4.56 5.04 8.11
40 2.80 2.87 3.80 3.90 4.08 4.28 4.73 7.60
35 2.60 2.70 3.58 3.67 3.84 4.02 4.45 7.15
Flow Rate Based Ground Water Temperature (assume 120°F set point)
Ground Water Temperature (°F)
Colder Climate Warmer Climate
9008877005 Product Preservers
®
SM1.0L Anti-Scale System
9008871005 Product Preservers
®
LG1.5L Anti-Scale System
Requires multiple units
Product Preservers
®
protects your tankless
heat exchanger from
scale formation. Refer
to the chart to the
right to properly size
for your application.