We hear the phrase that water is the universal solvent. Why? So many materials dissolve in water due to its unique molecular structure. So it does not seem like a fluid to be used in a hydronic heating system made of many different materials. Water does have many advantages as a heat transfer material. It is cheap, safe, easily acquired, has a wide liquid temperature range, and is generally non-toxic.
With water coming from so many different sources worldwide, it can contain many different minerals. It is the wide combination of these minerals that water gathers as it flows through our aquifers that needs attention.
Many of the common minerals found in water will cause issues in hydronic systems. The hardness of the water, and minerals that fall from solution, are the most common concerns. As the minerals precipitate out, they can stick to and coat the surfaces of our boiler heat exchangers, for example. This coating forms until enough build-up reduces the heat exchange and the metal of the heat exchanger breaks down. A classic example is what you see when you drain an old tank-style water heater. Some of the material that can be found in tap water cause further concern…like chlorides.
Boiler and tank manufacturers are now listing the most harmful minerals as well as acceptable levels. Calcium, magnesium, chlorides, and sulfates are commonly listed. The ph level is also required to fall within a range, something like 6.6 and 8.5 according to one boiler specification.
Failure to maintain the proper water chemistry can cause loss of efficiency, noise, wear, premature failure, and most important to the consumer, lack of warranty.
So the industry needs to first get some training on what to look for, how to measure levels, and what to do with water that does not meet the quality required to assure warranty coverage.
Most agree that starting with good quality water is one key. It is possible that the water in your town is of sufficient quality. But if you are not testing, you are guessing. Know also that water quality in an area can vary season to season. One of the most noticeable changes in water quality can be linked to the road deicing chemicals used. Back in the day, rock salt, maybe blended with sand, was the go to deicer. Nowadays chloride blends are being used in may states. Chlorides have a wider melt range, and can be applied as a liquid. They often get applied before a snowstorm, or icing condition as a proactive measure.
Guess where these chlorides end up? In our water supplies, via lakes, rivers, and even well sources. Many water sources have been seeing a spike in chlorides. States like Wisconsin and Minnesota have been monitoring this carefully as the aquatic life in their thousands of lakes and rivers are being affected by the elevated chlorides, as well as the flora and fauna.
There is a fairly simple fix for water that is not of sufficient quality for use in hydronic systems. Both deionizing and chemical treatments are available to help bring water back to a hydronic-friendly heat transfer fluid.
Flush your systems. Consider a hydronic detergent to rid the system of oil, flux, dirt, etc. Test the water for the final fill, and treat as required, or haul quality water from another source.
You will be hearing more about boiler water quality as manufacturers of boilers, tanks, pumps, valves, etc. start reexamining warranty returns that have been compromised by fluid quality. It will be a tough conversation to have with a home or building owner if an expensive component fails prematurely due to fluid quality and the warranty is refused.
Hot Rod is currently the training and education manager for Caleffi North America. He owned his own contracting company, Show Me Radiant Heat & Solar, Rogersville, Mo., having been a plumbing and heating contractor since 1978.