FRP vs Galvanized Steel Cooling Towers: An Honest Comparison

We build fiberglass (FRP) cooling towers, so you already know which way we lean. This page is meant to help you decide anyway — including in the cases where a galvanized steel tower is the better buy.

Most packaged cooling towers sold in the U.S. are galvanized steel. FRP and galvanized both cool water the same way; at the same design conditions, the shell material has little effect on thermal performance or fan energy. Where they differ is in four places: how they resist corrosion, what they cost over their life, what the warranty actually covers, and what maintenance they demand. Those are the four sections below.

If you want the shorter background on why we build in fiberglass, read Why Choose a Fiberglass Cooling Tower? This page goes deeper on the numbers and the trade-offs.

The short answer

1. Corrosion resistance

This is the core difference, and everything else on this page follows from it.

How galvanized steel holds up

Galvanized towers are steel sheet coated with zinc. The zinc corrodes slowly and sacrificially, which protects the steel underneath. That works well, but the zinc is consumed over time, and the rate depends on your water and your air:

• White rust on new towers. Fresh galvanizing needs to be passivated during the first weeks of operation, with pH held in a controlled range. Run a new galvanized tower at high pH without passivation and the zinc can form a white, porous deposit and wear away early. Water treatment suppliers publish whole bulletins on preventing it.
• High-pH and high-cycle operation. Running more cycles of concentration to save water pushes pH and dissolved solids up, which is harder on zinc.
• Chlorides and salt air. Coastal sites, de-icing salt, and high-chloride makeup water accelerate attack.
• Weak points. Cut edges, seams, fasteners, and the basin floor, where water sits all the time, usually go first.

Once the zinc is gone, bare steel corrodes in a warm, wet, oxygenated box. Owners respond with basin coatings, patches, and stainless or coated replacement panels. Many manufacturers offer stainless steel basins or premium coatings as upgrades for exactly this reason.

How FRP holds up

FRP has no metal in the shell or basin, so there is nothing to rust. Water chemistry, salt air, and treatment chemicals that attack zinc do not attack the laminate in the same way. CTS towers are laminated with unsaturated polyester resin and finished with a gel coat that protects the surface from UV.

FRP is not indestructible. Over decades the gel coat can chalk or fade in strong sun, and physical impact can crack a panel. Those are cosmetic or repairable issues, not structural corrosion that spreads.

2. Lifecycle cost

Galvanized usually wins on purchase price. FRP usually wins on cost of ownership. Which one matters more depends on how long you will run the tower.

Shell material does not change your largest cost, which is energy for the fan and pump. A well-sized tower in either material saves the same chiller and process energy. Our ROI & Savings page covers those savings and how to build the business case. The material decision affects the costs below.

When the math flips

Lifecycle math only favors FRP if you keep the tower long enough to avoid the corrosion costs. If you expect to sell the building, close the line, or replace the system within about ten years, the lower purchase price of galvanized may never be paid back. In that case, buy the cheaper tower. We would rather tell you that than sell you a 20-year warranty you will not use.

For a longer horizon, compare the two options on the same basis. Add the purchase price, delivery and installation, and a realistic allowance for coatings and corrosion repairs in years 8 through 20. Then compare against what you would pay to replace the steel tower early. For the longest-running case we know of, two CTS T-220 towers on Florida's east coast stayed in service for 42 years. See cooling tower life expectancy.

3. Warranty

Warranty length is the easiest way to see what a manufacturer expects its tower to survive. Read the terms by component, not just the headline number.

The CTS warranty

For orders placed within the United States, the published CTS warranty covers:

• 20 years on the FRP casing and cold water basin
• 2 years on PVC fill
• 1 year on fan motors, major drive components, and internal moving parts

International orders carry 18 months from shipment or 1 year from start-up. The long coverage applies to the parts FRP protects, the shell and basin. Moving parts carry normal mechanical coverage because they wear out on any tower, whatever it is made of.

What to ask about a galvanized tower's warranty

Packaged galvanized towers commonly carry a shorter standard warranty, with longer coverage sold as an option or tied to an upgraded basin material. Terms vary by manufacturer, so ask each supplier these questions in writing:

• How many years cover the basin and casing against corrosion or perforation, not just against defects?
• Does corrosion coverage require a specific water treatment program, passivation records, or pH limits?
• Is long coverage only available with a stainless steel basin or premium coating, and what does that upgrade add to the price?
• Is the coverage parts only, or does it include labor, rigging, and downtime?
• Is it prorated?

Our warranty is also replacement parts only, with the exclusions listed on the warranty page. Compare like for like.

4. Maintenance

FRP does not make a cooling tower maintenance-free. The mechanical side of the tower needs the same care no matter what the shell is made of. The difference is in the structure.

Use our seasonal and annual maintenance checklist for either type. CTS stocks replacement parts for every tower we build, including towers installed decades ago.

Other differences worth knowing

Weight and installation

FRP is light. A CTS Model T-260 (60 tons) has a dry weight of 437 lbs and ships completely assembled. Even the 400-ton Model T-2400 weighs 4,786 lbs dry. Lighter towers mean smaller cranes and fewer roof structure upgrades, which helps on rooftops and older buildings. Always design supports for operating weight, which includes the water.

Fire and code requirements

FRP and PVC are combustible, and steel is not. Some insurers and owner specifications require FM-approved cooling towers or specific fire protection. If your project has that requirement, raise it before you choose a material. It can decide the question on its own.

Very large capacity

CTS packaged towers run from the 3-ton Model T-23 to the 1,500-ton Model T-3500, with multi-cell layouts beyond that. Very large plants are often better served by field-erected towers, and those are a different category.

Water temperature

High hot-water temperatures limit fill and some resins before they limit steel. If your water enters the tower unusually hot, tell us the temperature. We will confirm suitability or recommend high-temperature options rather than guess.

Frequently asked questions

Do FRP cooling towers last longer than galvanized steel towers?

In most open-loop applications, yes. Galvanized towers usually reach the end of their life when the basin and casing corrode. FRP does not rust, so the structure tends to outlast the mechanical parts. CTS FRP towers are designed for 25–30+ years, and the casing and basin carry a 20-year warranty.

Is a galvanized cooling tower cheaper?

Usually, at purchase. Over 15–20 years, recoating, corrosion repairs, and early replacement often cancel the upfront savings. If you plan a short ownership period, galvanized may be the more economical choice.

Does FRP improve cooling performance or energy use?

Not by itself. Thermal performance depends on the fill, airflow, and water distribution, and on sizing the tower correctly. FRP keeps that performance from degrading because of structural corrosion. Use our sizing guide to choose the right model.

Can I replace a galvanized tower with an FRP tower?

Yes. This is one of the most common reasons people call us. Send us your flow rate, water temperatures, location, and current footprint, and we will match a model. See our replacement and retrofit guide to decide whether to replace or repair first.

Is stainless steel a better option than both?

Stainless resists corrosion much better than galvanized, but it costs considerably more. It can also pit in high-chloride water, which is exactly what concentrates in a recirculating tower. Stainless basins make sense in some specifications. For most commercial and industrial jobs, FRP gives comparable corrosion resistance for less.