Why is there foam in my cooling water?

Author: Mark Rohac | Territory Manager


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.

Knowledge Direct

Want to share this topic and more with your team?

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.

Mark Rohac is a Professional Engineer and Certified Energy Manager with a degree in Mechanical Engineering from McGill University. Mark is a Territory Manager with over 20 years experience in the design and implementation of water solutions for our industrial, commercial and healthcare clients. In his free time, Mark enjoys being with his twins and making them laugh with his ridiculous humor.

Connect with me on:

Enjoy Reading This? Why Not Share It With Other’s

Share on facebook
Share on twitter
Share on linkedin
Share on google

Knowledge Direct

Want to share this topic and more with your team?

Related Posts

Waterside Inspections Sludge Example
Boiler Water Treatment

A Guide to Waterside Inspections

Visual inspections provide an indication of the overall health of your system and validate the results of your water treatment program. It is crucial to catalogue inspection reports to allow you to determine if the current condition indicates equipment status is unchanged, improving or degrading.

Read More »

Leave a Reply

Request Access

Download Report – Best Practices for Energy Efficient Boiler Plan Design, Operation and Control

On-Site Seminar Request Form

Checklist for Minimizing Legionella Risk Download (2018)

St. Mary Mercy Livonia Hospital Case Study

Head Office

Access Request

Legionnaires’ Disease Guide for Employers and Building Owners Download

Aqua Analytics DK-12000 Download

Checklist for Minimizing Legionella Risk Download

Purchaser Checklist for Setting Base Case Scenario Download

Engineering Notes – Deaerator Download

Tower & Chiller Lay-Up Procedure Download

Blog Newsletter Subscription

Contact Me

Service Locations

Ohio Sales Office

Michigan Sales Office

American Head Office