A cooling tower usually needs replacing, not repairing, when its structure, casing or basin is failing, or when rebuilding the fill, drift eliminators, fans and basin would cost close to what a new tower costs. Most of the wearing parts inside a tower can be replaced on their own. The decision comes down to whether the shell holding them is still worth putting new parts into.
What a cooling tower is doing
A cooling tower gets rid of a building's heat by evaporating water. Warm condenser water from the chiller is spread over the fill, a pack of sheets or splash bars that breaks the water into thin films. A fan pulls air through, some of the water evaporates and the rest cools and falls into the basin, where it's pumped back to the chiller. Drift eliminators catch droplets before they leave with the air.
The Department of Energy's cooling tower guidance lays out where the water goes: evaporation, drift and blowdown (water drained off to keep dissolved minerals from building up), all of it replaced by makeup water. It also notes that dissolved solids that aren't carefully controlled cause scale and corrosion. That's a big part of why towers wear out.
The parts that wear out, and what each one means
| Component | Signs of trouble | Usually |
|---|---|---|
| Structure and casing | Rotted wood framing, rusted-through steel, cracked or sagging panels, a structure that moves under load | Replacement territory |
| Basin | Leaks, corrosion, pitting, failed seams | Repair or line if localized; replace if widespread |
| Fill | Scale buildup, clogging, collapsed or broken sections, poor cooling | Replace the fill |
| Drift eliminators | Broken, missing or out-of-place sections, visible mist leaving the tower | Replace, ideally with high-efficiency eliminators |
| Fans, motors, gearboxes | Vibration, noise, oil leaks, worn bearings | Repair or replace the part |
| Water distribution | Clogged or missing nozzles, uneven flow over the fill | Repair |
A tower with a sound structure and basin can often be rebuilt with new fill, drift eliminators and mechanical parts. A tower whose structure or basin is failing can't be fixed by new parts inside it.
The water safety side
Cooling towers can spread Legionella, the bacteria behind Legionnaires' disease, if they aren't kept clean. The CDC's cooling tower toolkit names sediment and biofilm, temperature, water age and disinfectant level as the main factors in its growth. It says that if Legionella is present, the tower's aerosol can carry it over miles. The CDC recommends high-efficiency drift eliminators, taking the tower offline for cleaning and disinfection at least once a year, and locating towers at least 25 feet from building air intakes.
ASHRAE Standard 188 sets out how building owners manage that risk with a water management program. An ASHRAE Journal summary of the standard explains that, for cooling towers, it covers equipment siting, new system startup, maintenance and water treatment.
This matters for the repair-or-replace decision. A tower with crumbling fill, hidden corrosion, low-flow corners or broken eliminators is harder to keep clean, no matter how good the water treatment is. If your water treatment vendor keeps fighting the same problem, the tower itself may be the problem.
Signs it's time to replace the tower
- The structure is decaying. Rot, corrosion or cracking in the framing, casing or supports.
- The basin leaks in more than one place, or patches keep failing.
- The repair list is long. New fill, eliminators, fan and motor, basin work and distribution all at once.
- It can't keep up. The chiller sees warmer condenser water than it should on hot days, even after cleaning and repairs.
- It's hard to keep clean. Scale, biofilm or debris keep coming back.
- The building has changed. The cooling load is different from what the tower was sized for.
Repair or replace: how to decide
Ask for two prices: a rebuild of everything the tower needs now, and a replacement. Then ask how many years each one buys. A rebuild on a tower with a sound structure can make sense. A rebuild on a tower whose casing or basin will need replacing in a few years usually doesn't, because you'll pay for most of a new tower and still have the old shell. Fold in what a new tower adds: high-efficiency drift eliminators, a design that's easier to clean, and new controls and metering.
How demolition and replacement works
- Plan the outage. Replacement is usually scheduled outside cooling season. If the building needs cooling during the work, temporary cooling has to be arranged.
- Check for hazardous materials. If the tower is old enough that asbestos-containing materials are a possibility, check before demolition. The EPA's asbestos rules call for a thorough inspection where demolition or renovation will occur, and notification to the delegated agency before demolition.
- Shut down, drain and disconnect. The tower is taken offline and drained, and condenser water piping, makeup and electrical are disconnected.
- Demolish and remove. The old tower comes apart and, on a rooftop, comes down by crane. Crane work follows OSHA's crane and derrick rules.
- Prepare the supports. The steel or structure under the tower is checked, repaired or modified for the new tower's size and weight.
- Set the new tower. The new tower is set, and piping, makeup, blowdown and electrical are connected. This is the time to add a conductivity controller and flow meters on the makeup and blowdown lines, which the Department of Energy recommends for controlling water use.
- Clean, disinfect and start up. The CDC calls for cleaning and disinfection before commissioning and startup. The water treatment program should be running from day one.
Mechanical permits apply. In the City of St. Louis, for example, mechanical permits are issued to licensed mechanical contractors certified by the city.
Or rethink the system
If your tower and chiller are both aging, it's worth asking whether you want a cooling tower at all. A full geothermal system rejects heat into the ground instead, so there's no tower to treat, clean or replace. See how geothermal HVAC works. If rooftop units are also part of the picture, see signs it's time to replace rooftop units.
Next step
We build and set cooling towers of all sizes, and we demolish and replace old ones. Request a free estimate or call 636-327-4238. If you're weighing geothermal, the geothermal calculator shows what it would cost after the federal credit.