Water Treatment

Does a Hot Water Heating Boiler or Chiller Need Water Treatment?

February 27th, 2019

The short answer is yes. The answer to why, is a bit more complicated. Throughout this post, common misconceptions about closed hot water heating systems will be explained and the answer to the “Why” will be provided.  Also shown will be how to recognize signs a system exhibits when needing to be cleaned, flushed, and chemically treated.  Finally, regular system maintenance suggestions will be given to keep a system running safely and efficiently.

Many boilers and chillers used for heating and cooling, in many kinds of buildings, are Closed Loop systems. Water is the main component within these systems which transfers heat or chilled water to regulate temperatures in specified areas within a building. The efficiency of heat/cool transfer is dependent on several important aspects of the system that must be regularly monitored and maintained. Why would a system that is closed to the environment need maintenance? Focus on the “closed” aspect of these heating and cooling systems, which is the first misconception to address. Unfortunately, though considered a closed system, there are both entry and exit points into such system. Why is this important to recognize? Entry or exit points give way to unwanted elements being introduced into the water system. The effects of undesirable elements are corrosion, deterioration of components, scale build up, and loss of heating/cooling transfer efficiency.

These elements or debris are introduced into the system through the make-up water supply when activated by the system water pressure regulator. Clean make-up water is needed due to water leaks and the reduced system pressure as detected by the pressure regulator. Often substantial leaks or losses can go undetected due to the make-up valve automatically making up the losses. Here is where the problems may begin. Commonly, expansion tanks have a volume of trapped air above the water. The oxygen dissolves into the circulating water, which is then introduced to the system. This introduces a small, but continuous supply of water containing dissolved oxygen. The dissolved oxygen causes rapid corrosion of iron and steel, forming layers of film, rust, or in extreme circumstances, under-deposit corrosion, all which can lead to pitting. Pitting can be catastrophic because it leads to rapid perforation or component failures. Corrosion also releases rust particles into the system water which can be particularly harmful on pump shaft seals and can erode other system components.

Pitting can be catastrophic because it leads to rapid perforation or component failures.

Other unwanted elements can consist of minerals and bacteria in lower temperature systems, as well as other organic or inorganic debris. Recirculating water carries water and any unwanted debris throughout the system. Once the undesirable debris is present in the closed system, they can wreak havoc if not properly maintained. Heating/Cooling transfer surfaces, pipes, tubes, and seals become coated with rust, microbial growth, scale deposits, and sludge which may affect the efficiency of the system. Another misconception is that adding inhibited glycol to a water system is efficient system water treatment alone. However, if glycol is added to dirty system water, the glycol will not be able to effectively protect the system. Recognizing the signs and symptoms a system may exhibit when needing cleaning and chemical treatment, along with regular systems checks is crucial.

Signs may include:

  • Appearance of dark, cloudy water with sediment at the bottom of water samples taken, indicating possible corrosion
  • Dissolved Iron or Total Iron test of system water resulting in significantly higher levels compared to the make-up water quality
  • Amount of sediment build-up found during inspection of filters
  • Deterioration of components—visually or mechanically
  • Loss of heat/cool transfer efficiency
  • Increased system run time
  • Apparent leaks
Recognizing the signs and symptoms a system may exhibit when needing cleaning and chemical treatment, along with regular systems checks is crucial.

If several of these signs have been recognized, the system may need to be cleaned, flushed, and chemically treated. A full system maintenance on a closed loop system every 2 years or so, will vastly improve the system’s performance and efficiency. Usually, it is recommended that chemical treatment occurs after the system is cleaned first. Cleaning the system would consist of removing the dirty water, a complete flush to remove sludge, rust deposits, and scale build up, with addition of a purging compound such as PURGEX L-24, to assist this process. Film forming corrosion inhibiting treatment is important to coat the internal surfaces of piping and equipment with a protective, monomolecular film that will protect the system metallurgy and enhance the efficiency of heating and cooling system. PACE BAR COR CWS series of corrosion inhibitors is recommended for all closed systems.

Finally, routine maintenance throughout the year consists of checking the pH of system water and glycol to ensure the fluid has not become acidic which needs to be done at least 2-4 times per year. Filter changes can be done monthly or quarterly for a clean system; weekly on systems that are known to be dirty. Regular visual inspection of equipment for leaks and installing an inexpensive totalizing water meter in the make-up line will help provide early detection of leaks. Lastly, it is important to check corrosion inhibitor concentrations regularly to ensure appropriate levels are being maintained for system protection.

Regular visual inspection of equipment for leaks and installing an inexpensive totalizing water meter in the make-up line will help provide early detection of leaks.
Regular visual inspection of equipment for leaks and installing an inexpensive totalizing water meter in the make-up line will help provide early detection of leaks.

Understanding misconceptions about closed loop systems will help to recognize signs and symptoms of a system that needs to be cleaned and chemically treated. Regular system maintenance consisting of filter changes, checking system fluid and inhibitors, and visual checks, will aid in preventing build up within the system and prolong the need for total system maintenance. PACE Chemicals has been servicing western Canada for 35 years and have AWT trained  water treatment specialists in Vancouver, Calgary, Edmonton, Saskatoon, and Regina, as well as Certified Water Technologists (CWT) in each province. Contact us today for an inspection, cleaning, and chemical water treatment for closed loop boiler and chiller systems.

By: Glenn Strelau, Sr. Vice President, CWT, AScT, LEED GA  

Co-Written by: Bri Dearwester