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Why Is There Foam In My Cooling Water?

Cooling water plays a vital role in transferring heat away from mission-critical equipment and processes, such as manufacturing, cold storage and air conditioning. Foaming in cooling water can occur rapidly, for no obvious reason, and not always predictable by routine system monitoring. Due to the design of evaporative cooling systems, allowing for high movement and constant air-water interface, a small amount of foam can be normal and not a cause for concern. However, in extreme cases, foam can exit an evaporative cooling system, be blown into the air and around the facility, making it visible to the surrounding population. Without proper understanding of the causes or remedies, flying foam can alarm the general population.

Understanding Foam

Foam formation requires the presence of a surfactant (surface active agent) to lower air-water interface surface tension. As well, movement such as turbulence is required to mix air into the water.

Foam can be white, or take on the color of contaminants present in the cooling water. It can be light and frothy, or thick like a slurry. These observations can be of use in helping troubleshoot the source.

Factors Causing Foam

There are many reasons for foaming to occur, either temporarily, or as a long-term phenomenon. Since each factor can compound the effect of the other, your water treatment supplier should help you take a comprehensive approach, considering all of the following.

  1. Excessively High Alkalinity Total Dissolved Solids (TDS) of recirculating cooling water is controlled by bleed-off of system water. High TDS can mean excessively high alkalinity levels, which lowers the surface tension of the water and can lead to foaming. In some cases, well-controlled dosing of acid can be used as an alkalinity suppressor allowing higher cycles of concentration while reducing the risk of foaming.
  2. Chemical Overfeed Maintaining water quality control parameters within recommended limits is important not only for economic reasons (using the right amount of chemicals – no more, no less), but also to lower the risk of causing foam by avoiding excessive chemical concentrations.
  3. Increased Bacteriological Activity Foam can often be a result of inadequate bacteriological control. Your water treatment supplier can advise on the best biocide to use and method of feed & control. The proper use of a bio-dispersant is key to keeping wetted components clean and free of biofouling.
  4. Reduction of Biological Activity Yes, foam can also be an indication that your bacteriological control is working! Once a bacteriological control issue is identified, correcting this with the use of a proper program can in itself lead to foaming. This is usually a temporary situation which improves as the system becomes cleaner. Use of bio-dispersants in particular, can cause significant foaming until biofilm is removed and good microbiological control is re-established.
  5. Process Contamination Cooling water can become contaminated, especially via leaking heat exchangers in food and chemical manufacturing facilities. Oil leaks can be another cause of foaming. A new foaming situation in such applications can be a useful tool pointing to failure of heat exchange equipment.
  6. High Degree of Suspended Solids Suspended solids are typically a result of scrubbing airborne contaminants into the cooling system by direct water to outdoor air contact, and can be removed with a properly sized filtration system.
  7. Change in System Dynamics Modifying anything in the cooling system, such as increasing flow rates, adding new production lines, or tying in used equipment with questionable past treatment, can result in deposits becoming dislodged and contribute to foaming.


It is always wise to have industrial defoamer onsite, as a short-term response to a foaming situation. Usually, very little defoamer is required to break the bubbles and release the air.

The following tips can help ensure foaming is not a cause for alarm at your facility.

  1. Ensure that all water quality control parameters are consistently within control limits.
  2. For improved stability, consider upgrading control equipment and filtration.
  3. Perform regular inspections and tests of heat exchange equipment.
  4. Perform pre-cleaning of any new sections added to the cooling system.
  5. Monitor the effect of each improvement and fine-tune the program accordingly.
  6. Add small amounts of industrial defoamer as a short-term urgent response tool as needed.


Due to the design of evaporative cooling systems, a small amount of foam can be normal. It is always wise to have industrial defoamer onsite, as a short-term response to a foaming situation. Usually, very little defoamer is required to break the bubbles and release the air.

Categories:  Water Treatment