A Guide to Cooling Tower Water Treatment Chemicals

Open cooling towers are essential for process cooling and HVAC in factories, commercial buildings, and data centers, especially in hot regions such as the Middle East, India, Southeast Asia, and Latin America. Warm, aerated water is ideal for heat rejection—but it is also ideal for scale, corrosion, and biological growth. Choosing the right chemicals for cooling water treatment helps keep this balance under control while protecting equipment and maintaining safe operation.

In practice, a cooling water treatment program is not a single product but a combination of scale control, corrosion control, microbiological control, and dispersion. Understanding how these chemical groups work together in cooling water treatment makes it easier to evaluate quotations and compare technical proposals.

1. Typical problems in open cooling towers

Most open systems share the same three core issues: scale, corrosion, and biological fouling. Good cooling water treatment aims to keep all three within acceptable limits over long operating seasons.

Scale formation. 

When water evaporates in the cooling tower, calcium, magnesium, and other salts become more concentrated. In hard or high-alkalinity water, this leads to calcium carbonate, calcium sulfate, or silica scale on fill packs, heat-exchanger tubes, and piping. Poor cooling water treatment allows these deposits to build up, cutting heat-transfer efficiency and forcing higher fan or chiller power.

Corrosion. 

Oxygen, chlorides, and low or unstable pH all drive metal loss in carbon steel, galvanized steel, and copper alloys. Without proper cooling water treatment, corrosion can lead to leaks, under-deposit attack, and unplanned shutdowns. In high-temperature climates, where cooling towers run for more hours each year, corrosion rates can become a serious cost and safety concern.

Algae, bacteria, and biofilm. 

Nutrients, sunlight, and warm water allow microorganisms to thrive on tower decks, fill, and basins. Effective cooling water treatment therefore always includes a biocide program to control algae, slime-forming bacteria, and biofilm that can hide underneath scale or corrosion products.

2. Scale control: phosphonates, polymers, and phosphates

Scale inhibitors are the foundation of most cooling water treatment programs. They work by interfering with crystal growth and keeping minerals dispersed so they pass through the system instead of depositing on surfaces.

Phosphonate-based products such as HEDP cooling water scale inhibitor and PBTC are widely used in cooling water treatment because they can tolerate high hardness and higher cycling of concentration. HEDP and PBTC help control calcium carbonate and calcium sulfate scale and also provide a useful corrosion-inhibiting effect on steel surfaces.

Polymers such as Polyacrylic Acid (PAA) and sodium polyacrylate act mainly as dispersants and threshold scale inhibitors. In cooling water treatment for hard, warm water, phosphonates and polymers are often blended: the phosphonate keeps scaling ions under control, while PAA keeps fine particles and iron oxides in suspension so they can be removed with blowdown.

In some systems, inorganic phosphates like Sodium Hexametaphosphate are also used. They can support cooling water treatment by tying up hardness and providing supplemental scale control, especially in soft-to-medium hardness water where corrosion is the main concern.

For buyers, the key is to select a scale-control package that matches local make-up water and target cycles. Reviewing the broader water treatment chemicals portfolio helps ensure that the scale inhibitor selected for cooling water treatment can also work alongside coagulants, antifoams, and other process additives already on site.

3. Corrosion inhibitors for steel and copper alloys

Even with good scale control, metals in a cooling circuit still need direct protection. Corrosion inhibitors in cooling water treatment create and maintain a protective film on steel, copper, and sometimes galvanized surfaces.

Organic phosphonates such as HEDP can act as both scale inhibitor and corrosion inhibitor when correctly dosed. For mixed-metal systems, it is common to combine a steel-focused inhibitor with copper protection based on azoles like benzotriazole (BTA). Some cooling water treatment programs also include molybdate or phosphate to strengthen the passive film in demanding conditions.

In real plants, corrosion control is rarely based on chemicals alone. Successful cooling water treatment also manages pH, alkalinity, and chloride, and it avoids operating conditions that strip films, such as frequent shutdowns without proper lay-up. Utilities and HVAC teams in high-temperature regions often prefer inhibitor packages that are stable under higher bulk water temperatures and extended running time.

4. Biocides and algaecides: keeping towers clean and safe

Microbiological control is another critical pillar of cooling water treatment. Open towers are exposed to airborne spores, dust, and organic matter, all of which support growth if not controlled.

Oxidizing biocides are the most common first line of defense. Products such as Sodium Hypochlorite, Trichloroisocyanuric Acid (TCCA), and calcium hypochlorite release free chlorine, which provides rapid disinfection. In cooling water treatment, oxidizing biocides are often fed continuously or intermittently, with residuals checked at the tower basin or return line.

Non-oxidizing biocides complement this approach. Quaternary ammonium compounds such as Benzalkonium Chloride and specialty products like THPS or glutaraldehyde help break down biofilm and control organisms that are less sensitive to chlorine. Many facilities rotate oxidizing and non-oxidizing biocides within their cooling water treatment strategy to reduce the risk of resistant populations.

For building HVAC and industrial plants, good biocide practice in cooling water treatment also supports hygiene goals and helps control risks associated with poorly maintained towers, especially in dense urban environments.

5. Dispersants and sludge control

Dispersants are frequently overlooked in cooling water treatment, but they play an important role in keeping systems clean. Dust, corrosion products, microbiological debris, and fine silt can settle in low-velocity areas if they are not kept in suspension.

Polymeric dispersants based on PAA or related chemistries prevent small particles from agglomerating and adhering to surfaces. In warm climates, where evaporation is high and airborne dust loads can be significant, adding the right dispersant to a cooling water treatment program helps keep tower basins and heat exchangers cleaner between mechanical cleanings.

When dispersants are combined with appropriate blowdown control, the solids load leaving the system becomes more predictable. For procurement teams, this can translate into more stable performance and fewer unplanned cleanings, which is often a key objective when evaluating cooling water treatment options.

6. Practical points for buyers and utilities engineers

From a purchasing point of view, cooling water treatment chemicals are easiest to compare when basic system data is available. Before requesting quotations, many plants prepare:

Recent make-up and circulating water analyses (hardness, alkalinity, pH, TDS, chlorides, silica).

Cooling tower type, tonnage, and typical cycles of concentration.

Materials of construction in critical equipment (carbon steel, stainless, copper alloys, galvanized).

Operating pattern (continuous, seasonal, daytime-only) and local climate conditions.

Current cooling water treatment program and any recurring issues (scale, corrosion, algae, odor, foaming).

Having this information ready allows suppliers to match phosphonates, polymers, and biocides to your actual conditions instead of offering a generic cooling water treatment package.

TJCY supplies cooling water treatment chemicals such as HEDP, PBTC, PAA, Sodium Hexametaphosphate, Benzalkonium Chloride, TCCA, and Sodium Hypochlorite to customers in high-temperature markets and supports them in matching formulations to local make-up water, system design, and operating habits instead of relying on a single generic treatment package.

If you would like to discuss a specific system, you can submit a form and we will contact you within 48 hours. You can share your water quality analysis and basic information about your cooling tower so that we can develop a customized cooling water treatment solution based on actual operating data.