Boiler Water Quality and Treatment

Boiler Water Quality and Treatment

February 23, 2022

Deaerator Tank

While there have been many innovations in boiler technologies over the years, the simplest and cheapest component – water – has the potential to shut the whole system down. The quality of the water going into a boiler system is critical to its operation, efficiency and longevity.

Boiler feed water may originate from surface-water sources such as rivers and lakes, or groundwater sources such as wells. While groundwater has fewer chemical contaminants than surface water, due to the natural filtering of rock and sediment, it tends to have higher mineral content due to the dissolving action of water. And excess minerals in a closed system boiler, particularly calcium, magnesium and silica, will lead to a number of damaging conditions.

“Many of our customers are dealing with hard water,” said Jason Hemphill, vice president of American Boiler & Mechanical. “We work closely with them to ensure their water is treated to optimize the performance and longevity of their boiler system.”

Boiler operators who are not treating their water properly, Hemphill warns, are vulnerable to these costly problems:

Corrosive Compound Build-Up

Build-up can be a problem in any water system, but it can be especially troublesome in boilers. Oxygen and carbon dioxide can accumulate in your system, and over time can cause corrosion.  Dissolved oxygen, salts, and carbon dioxide can build up quickly.  This can usually be avoided by using feed water that is alkalized to a pH of 9.0 to 10.0.  Using water with the right pH can also help form a thin layer of magnetite on the boiler waterside surfaces to avoid further damage to the metal. Failure to remove oxygen from the incoming boiler feedwater can cause serious and widespread pitting and corrosion in boiler tubes, especially in the economizer section of the watertube boilers, drastically reducing their useful life expectancy.

Boiler Deposits/Scale

Compound deposits (also called scale) in boilers will reduce its efficiency and reliability.  Deposits don’t just reduce the amount of heat transfer in the boiler; it also slows water flow and blocks boiler tubes.  Salts and minerals that remain in the boiler will get overly concentrated, producing a nasty looking grey-ish white build up inside the boiler. Eventually the boiler won’t function well, delivering inconsistent water temperatures, flow and may lead to tube overheating.

Stress Corrosion Cracking/Caustic Embrittlement

The buildup of caustic chemicals may not just decrease the efficiency of boilers; they could actually cause significant damage to pipes and to the boiler itself. Caustic embrittlement usually occurs at temperatures of 200 to 250 degrees Fahrenheit, a temperature that can be easily reached in any boiler. This problem is particularly troublesome because it usually occurs in important steel boilerplates,  which can be the most stressed and vulnerable part of your boiler.

To prevent such problems AB&M recommends frequent boiler water testing.  For boilers where adding chemicals is the only type of treatment, daily testing is recommended. Where operation are in steady state, weekly testing will usually be sufficient as long as no upset is discovered. Following an upset, more frequent testing is needed to ensure the problem is corrected. For more complex water treatment systems, such as those with water softeners, and especially ion exchange units with regeneration, more frequent testing may be necessary, possibly every few hours.

For boilers that are encountering problems due to poor water quality, AB&M offers repair and/or equipment replacement options to promptly get the system running again.

For more information on optimizing your boiler’s water quality and system performance, as well as issues or questions regarding process piping, contact us at 800-235-5377 or through our website at