HEATING AND COOLING SYSTEM WATER QUALITY
By Ernie St. Pierre, LSG, Technical Consultant
To ensure a water heating and/or cooling system operates and functions properly over its lifetime, the water that circulates within the system must be monitored for its condition. The condition of the water plays an extremely important role in the life of a system. If the water is not treated to within the guidelines set forth by the manufacturer and maintained properly, the system can and will often suffer severe damages as early as in the first year of operation.
Boiler specific failures resulting from untreated water include overheating, failure to produce sufficient hot water or steam, lower flow rates, severe internal corrosion and an increase in fuel consumption. Cooling tower specific failures may result in freezing, internal corrosion, a buildup of minerals and contaminants, and premature failures.
Untreated water, even that which is supplied to a facility by the local municipal water provider, can contain dissolved solids which can and will cause scale deposits on the heat transfer surfaces of the system. Dissolved solids that create scale will collect on the watersides of the boiler or heat transfer surfaces inside the system leading to inefficient operation and/or failures. The scale also reduces the flow areas within the system, which increases the pressure drop and results in low volume and potential downstream equipment failure.
In both hot water and steam systems within boilers, the water that is being fed contains dissolved gases, including two (2) common damaging gases (carbon dioxide and oxygen). These gases commonly react within the watersides of a boiler and cause corrosion of the system's internals. These reactions occur within the interior of the boiler's waterside and are not visible externally. When these gases are not removed from the feed water and are thus allowed to enter the system, they will cause corrosion, which can permeate the interior and cause leaks. Typically, when internal corrosion occurs, one suffers a catastrophic failure of the vessel and a complete system replacement is required.
Several other impurities within boiler feed or cooling tower feed water include chlorides, magnesium, sulfates, sodium and calcium bicarbonate. All of these impurities combine to form what is known as hardness of the water. If deposits of calcium and magnesium go untreated they will coat a heat transfer surface internally and block the flow within tubes and pipes. Over time, and depending on the level of impurities, a tube as large as two inches could become restricted to an opening as small as three-quarters of an inch.
Typically, manufacturers prescribe the allowable water conditions a piece of equipment is designed to operate within. Many manufacturers will exclude a warranty for a leaking vessel if proof of water conditions cannot be provided. Therefore, water testing should be performed by companies familiar with the standards specifically set forth by boiler manufacturers, as these requirements will typically be different than residential water conditioners found in homes.
Both residential and commercial systems are vulnerable to water conditions and manufacturers of residential boilers are now addressing water quality before a warranty is provided.
Cooling Towers and Chillers:
Cooling towers and chillers can also be affected by poor water conditions. Cooling towers can be breeding areas for airborne illnesses unless the water is tested and treated to prevent harmful bacteria growth. Extensive water testing must be performed periodically to ensure that the guidelines set forth by the equipment manufacturer are adhered to. Whenever water is added to a system or replaced in an HVAC system the condition of the water should be tested to assure it is within the guidelines set forth.
For more information about this topic, please contact Ernie St. Pierre, LSG Technical Consultant, to discuss Boiler System Water Quality or any other HVAC/Mechanical matter at 866.899.8756 ext. 712 or write to him at