Cooling Tower Water Treatment

WaterCare has over 30 years of experience working with HVAC and industrial cooling tower water treatment systems. Water treatment is essential for creating a safe, efficient, and cost-effective system. We save facilities managers and operators £1,000s wasted on energy, chemical, and maintenance charges by preventing scale, corrosion, and biological fouling.

Not looking for water treatment for your cooling tower? Our commercial water treatment covers every part of your industry.

How Cooling Tower Systems Work

A cooling tower system takes hot water from the industrial process, cools it down, and then exports it back into the system for reuse. This process is called evaporative cooling. as the hot water is cooled by the air as it falls to the bottom of the basin, hot moist air rises out of the tower, but cooling efficiency can be further improved by the air either being forced or induced.

There are different types of systems for different applications:

Power utility services use once-through cooling water systems, which can be located near rivers or coastlines. Only one complete cycle of the cooling mechanism is completed before the water is released.

Cooling water is recycled and reused in open recirculating cooling water systems. In an open-circuit cooling tower, the air is circulated through the fill pack while the water that needs to be cooled is spread over it. This lowers the temperature of the remaining circulating water by causing a tiny amount of cooling water to evaporate. The cooled water is collected at the base of the cooling tower and then recirculated to the plant or process needing to be cooled and the warm, humid air is discharged from the tower into the atmosphere.

Water Quality Evaluation and Care

Our professional, highly-trained consultants can survey and carry out a site water services risk assessment on your water systems to comply with the current legislation HSG274 and ACOP L8 Rev 4 before offering a managed program to control site-specific risks and issues.

WaterCare Solutions has a bespoke selection of high-performance chemical products specifically designed to:

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Control scale formation

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Protect against the damaging effects of corrosion

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Reduce fouling

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Control microbial growth like the Legionella bacteria and Pseudomonas

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Control pH

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Treat wastewater prior to discharge

How Evaporative Condensers work

Evaporative condensers use the same evaporative cooling principle as cooling towers but incorporate a heat exchanger in which a fluid is cooled by a secondary recirculating system that distributes water over the heat exchange coil and a portion of this water is evaporated (Figure a).  The coolant is used to provide the heat necessary to evaporate the water, and the heat is then transmitted to the airstream’s water vapour, which is released into the atmosphere similarly to a cooling tower. The coolant is often a refrigerant gas but, where the coolant is water or a water/glycol mixture, these systems are sometimes referred to as closed-circuit cooling towers.

A closed-circuit cooling tower is designed to prevent the water to be cooled from becoming contaminated by coming into contact with the atmosphere. This can be achieved by linking to a separate heat exchanger or by a closed-circuit cooling tower (Figure b). The latter has a heat exchanger through which the water to be cooled flows and there is a secondary recirculating water system providing the cooling effect in the same way as an evaporative condenser.

Why cooling tower systems need water treatment

Pre-treatment plants removes impurities from the feedwater and hydro cyclones can be used to remove suspended solids from the re-circulation water and the blowdown.

Water treatment is used to ensure compliance with HSG274 part 1 by preventing scale, corrosion as well as preventing microbiological growth and providing legionella control. A cooling tower must be maintained to keep running costs low and sustain high cooling efficiency. Unplanned downtime and reduced plant productivity affect business and cause headaches for any facility manager.

Cooling water treatment is effective at minimising:

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Deposit formation

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Microbiological growth

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Chemical costs

Any treatment programme also ensures safety and compliance with environmental and water conservation.

Table 1.1 HSG 274 part 1 shows Typical cooling water desired outcomes for the above objectives.

Any treatment programme must also ensure safety and compliance to HSG274 part 1 and A.C.O.P L8 rev 4.

Table 1.8 in HSG274 part 1 shows Typical minimum on-site monitoring and analytical checks for cooling water treatment.

Cooling tower water treatment for a nuclear power plant

Our Services

Water Treatment Services

Our Water Treatment Services provide a wide variety of high-quality water treatment solutions, that will help with Legionella Control, Industrial and Commerical Waters etc. Discover more...

Water Hygiene                Services

Our water hygiene services, provide risk assessments, and inspections to evaluate the hygiene level of your water. We will help you stay compliant with the codes of practice. Read more...

Water Disinfection & Cleaning Services

Water disinfection and cleaning services is an essential to maintain compliance and reduce the levels of microbiological fouling within water systems. Explore further...

Water Dosing & Control

We offer a broad range of water dosing and control chemical applications, that we can advise on the best control solutions for you on-site. Continue reading...

Water Risk Assessment

Stay up-to-date with the regulations of water risk assessment. Our legionella risk assessment provides practical advice and guidance to duty holders. Learn more...

Pre-Treatment Plant

Our Pre Treatment Plant is a crucial part of any water treatment programmed. This is due-to the improved efficiency, and reduction in water and chemical usage. Read on…

Analytical Sampling

For our Analytical Sampling services, we use only independent NAMAS/UKAS accredited laboratories for analysis of deposit or water samples – verifying independent result are carried out. Discover more…

Air Hygiene

Our Air Hygiene services is not only a statutory requirement, but providing a clean, safe working environment for employees and visitors is beneficial. Explore further…

Watercare solutions

Common water problems that cause cooling inefficiencies

Sludge & Grime

The cooling tower because of the contact between air and water will basically scrub out any airborne particulates that enter the tower. Dirty air comes in and clean hot air leaves the tower. These deposits can block cooling tower infill packs and form sludge deposits in the sump. These deposits can promote bacterial growth and increase chemical consumption. This is why regular inspection and cleaning/disinfection ais required.

Where there is heavy particulate matter ingress into a cooling tower a hydro cyclone should be considered to remove silt and sludge from the recirculating water.

Microbiological deposits

Bacteria and algae deposits block the free flow of water and air in the cooling tower. Over time, the weight can break the components of the tower. As the largest source of cooling tower fouling, these deposits (with mud and grime) hurt performance the most.

Scale deposits

Scale impacts heat transfer and directly impacts the efficiency of your tower. Scale forms when a dissolved substance becomes greater than solubility in the water. The biggest culprits are:

  • Calcium sulphate
  • Calcium phosphate
  • Other calcium salts


Corrosion occurs when metal encounters oxygen and moisture. Systems with recirculating cooling water are more prone to forms of corrosion and rust. The quantity of the electrolyte increases the corrosiveness of the water when it is exposed to air.


Water flowing in the cooling towers can cause foam to form. Even with the aid of fans, if this overflows, it may penetrate the atmosphere or harm the tower’s exterior. Foam also causes more sediments and fouling.

Benefits of water treatment in cooling towers

Regular and effective water treatment enables your operations to run at full efficiency, is cost-effective and reduces the risk of breakdowns.

Reduces water consumption

The requirement for makeup water is reduced and higher dosage levels. Scale and microbiological deposits can’t form and the cycles of concentration can be maximised to increase productivity with the proper pre-treatment, in addition to levels of water treatment.

Reduces energy consumption

In the same way, by removing scale and fouling, less heat is needed in the exchangers. As the system doesn’t have to work as hard to cool, less energy is consumed.

Reduces chemical use

Removing suspended particles reduces the reliance on chemical treatment.

Lower maintenance cost

A side-stream filtration unit will reduce maintenance costs and production downtime as it allows for longer operation periods before being required to be taken offline.

Control of biological growth

One way to prevent health problems, including legionnaires’ disease, is to regularly monitor the cooling tower to prevent biological growth. It is the duty holder’s responsibility to perform continuous checks on cooling towers.


How Water Treatment Works for Cooling Towers

A cooling tower treatment system can be achieved by following these crucial steps:

Before and after a water treatment program

Side-stream filtration

Contaminants that arrive through are removed by side-stream filtration. These filters operate constantly in small increments, allowing for an increase in water and energy efficiency, with less water discharge and scale development.

Blowdown treatment

Recirculating systems help to post-treat water using ion exchange or reverse osmosis before it is sent back to the tower to be used again. Systems that release water into sewage lines must adhere to rules established by their water supplier.

Treat the makeup water

Makeup water is obtained straight from an outside source, such as reclaimed wastewater from manufacturing facilities, borehole water from rivers or wells, or even municipal water. It is essential to treat the water before being permitted to replenish evaporated water in the system. Hardness and sand are typically eliminated during treatment, and the pH is stabilised.


Filtration is a great treatment for cooling towers as it is effective at removing sediment, turbidity, and other organic matter. Certain filtration options enable particles under one micron to be removed and acts as protection of the ion exchange from fouling in pre-treatment.

Chemical addition

Another ideal water treatment solution, which will save you exponential costs, is to add a range of chemicals to balance the water’s properties. Your costs will be reduced on the purchase of chemicals when thorough pre-treatment is adhered to, as the number of chemicals you will require will be reduced.

Standard chemical usage includes:

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Scale and Deposit formation

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Microbiological growth

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Chemical costs

Examples of water treatment programmes

It is important to understand how your cooling tower operates to know what treatment programme to use. The right treatment programme will depend on the size, purpose, and components of your cooling tower.   The general sizes of cooling towers can be defined as:

Small-sized towers = less than 88 kilowatts (25 tons)

Medium-sized towers = Between 88 to 352 kilowatts (up to 100 tons)

Large-sized towers = 352+ kilowatts (100+ tons)

Cycles of Concentration (COC)

The COC plays a significant role in all towers and can reduce silica and calcium salt build-up, when being controlled manually or automatically by the blowdown. Chloride levels can become corrosive and cause pitting corrosion the COC are limited dependant on the design and level in the make-up water to prevent this.

Water Quality

It is essential that testing and treating water is performed to ensure the proper functionality of the cooling tower system. Table 1.8 in HSG274 part 1 shows typical minimum on-site monitoring and analytical checks for cooling water treatment to maintain water quality.

Understanding the water constituents influences the entire treatment.  It may be necessary for the removal of hardness or silica, as well as adjusting the pH levels, depending on the quality of the treatment.

Always consult a professional, such as Watercare Solution, to assist you in choosing the correct treatment programme for your cooling water tower.

Conducting a Water Hygiene Service with a vial half full of water

Common water elements regulated

The example treatment programme shows that there are many aspects of water we need to control. Some of the most common aspects to regulate include:


The concentration of the water, which is measure by titration with a standard acid solution.


Is a corrosive ion, that may be limited to depending on the system metallurgy. Chloride levels can also be applied to measure concentration factors and may indicate brine loss, from a malfunctioning water softener where fitted.


Contributes to scale in the cooling tower and heat exchanges.


Soluble iron in the flowing water can advance the growth of legionella in the system.

Organic matter

Encourages microorganism growth, leading to fouling, collisions, and other system issues.


Causes hard-scale deposits, which are more difficult to remove safely than calcium & magnesium scale.


Corrosive to metals, like chlorides.


Total dissolved solids contribute to scaling, foaming, and corrosion.


Total suspended solids are contaminants that are undissolved in the system and can cause biofilms, corrosion, and scaling.

Save money and time with a WaterCare treatment plan

Legionnaire’s disease can be brought on by scale, rust, and fouling. You have a duty to safeguard all users from dangerous bacteria because you are engaged with the water supply systems for your business. A WaterCare treatment plan guarantees your cooling towers run as efficiently as possible while also assisting you in fulfilling your responsibility.

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