Why Is My Water Cooler Freezing Up?

On this page (9 sections)

1. What usually causes a water cooler to freeze up?
2. How do you tell a stuck thermostat from a blocked vent?
3. Why does a water cooler freeze water in the first place?
4. Which settings and placement mistakes cause the problem?
5. What should you do once the tank has frozen?
6. When is the thermostat or fan the real culprit?
7. Is frozen water safe to drink after a cooler freeze?
8. Can a cold room make a water cooler freeze?
9. How do you stop a cooler freezing up again?

Your water cooler is freezing up because its thermostat is stuck on cooling, its vent or fan is blocked, or the cold control is set too high. Turn the cooling switch off and unplug the unit before you look inside.

The good news is that a frozen cooler is rarely a mystery. Most cases trace back to one of a few parts, and you can sort out which one with a short set of checks before calling a repair shop.

This guide walks through the causes in the order you'll find them.

What usually causes a water cooler to freeze up?

A failed thermostat is the most common cause. That part tells the compressor when to stop cooling, and when it sticks closed, the compressor keeps running and the tank keeps getting colder.

Blocked airflow runs second. A cooler pushes cold air around its tank and needs its vents clear to move that air evenly.

Dust, a cabinet pushed against the wall, or items stacked on top all trap cold in one area.

Other causes worth checking:

• The cold control sits at its highest setting, so the unit never shuts off.
• A cooler with a fridge compartment is set so cold that its own chiller ices up.
• The room itself is very cold, near or below freezing.
• A clogged fan or a fan that has stopped turning.

If the water is warm instead of frozen, the cause sits on the other side of the system. Our guide on a water cooler not cooling water covers the checks for that case.

How do you tell a stuck thermostat from a blocked vent?

Feel the air at the vent and listen for the fan. Clear air movement and a running fan point away from airflow and toward the control.

Start with the vent. Pull the cooler out from the wall so it has open space behind and above it.

Vacuum loose dust from the grille and from around the fan, then switch the cooler on and feel the air coming through.

If the vent and fan are clear but the tank still freezes, the thermostat is the likely suspect. A stuck thermostat keeps the compressor running past the set point, so you'll often hear steady compressor noise with no pause.

A quick test without tools

Turn the cold control to its lowest cooling setting and let the cooler run for an hour. If the tank still ices over, the dial isn't controlling the compressor and the thermostat or control board needs attention.

Don't keep running the cooler once you suspect a stuck thermostat. A frozen tank can crack the liner and stress the compressor, and both are expensive fixes.

Why does a water cooler freeze water in the first place?

Cold water is the whole job, so the cooler only freezes when the cooling control loses its stop signal. A working unit chills the tank and then rests.

The freezer case only happens when that rest never comes.

A cooler cools water with a small compressor and evaporator coil wrapped near the tank. A thermostat reads the tank temperature and opens the power circuit once the water reaches the set point.

When that switch welds shut or a sensor sends a false cold reading, the compressor keeps working.

Some models pair that thermostat with a fan to spread cold air. If the fan slows, one part of the tank gets very cold while the rest stays warm.

That uneven chill is why you sometimes see ice in one corner and cool water everywhere else.

Which settings and placement mistakes cause the problem?

A cold control set to maximum and a warm spot in the room both push the cooler past its normal range. Fix the setting and the location first, because both are free.

Check these spots:

• Cold control: most units have a dial or a small switch. Move it toward the middle, not the coldest end.
• Cooling switch: some coolers have a separate cooling on/off switch that stays on by accident.
• Room temperature: a garage or unheated room below about 50°F (10°C) can chill the tank without any part failing.
• Direct sun and heat: a unit next to an oven or a sunny window runs longer and less evenly.
• Blocked cabinet: pushing the cooler into an alcove with no rear clearance traps warm air and makes the compressor work harder.

Cold air is heavier, so a vent pointed at one side of the tank will freeze that side first. Repositioning the unit often evens out the chill without any repair.

What should you do once the tank has frozen?

Switch the cooler off and unplug it, then let the ice melt on its own. Don't chip at it with a tool or pour hot water into the tank.

Plan for a few hours of melt time, and keep towels or a shallow tray under the dispenser in case water drips. Open the door or lid so air can reach the tank.

Once the ice is gone, drain the tank completely. Then clean the tank and the water lines before the cooler goes back into use.

A frozen tank can hold stale water and loosened scale, and cleaning now saves a bigger job later.

How to clean and descale after a freeze

Drain, clean, rinse, and flush the lines. Use a cleaner made for water dispensers so you remove scale and film without leaving a taste behind.

The IMPRESA pack has two 8 fl oz bottles. IMPRESA says the formula is unscented and tasteless, so it won't leave a residue behind in the tank.

It works with top and bottom loading coolers and mini dispensers.

The Yadool kit covers top and bottom loading coolers and most dispenser styles. Yadool says you pour it in, wait about 15 minutes, and rinse.

The 5.07 fl oz bottle suits one or two cleans.

Pristine's H2OK is a concentrated cooler cleaner for keeping the tank and lines fresh between deeper cleans. Follow its directions for the mix and the soak time.

Rinse the tank well after any cleaner and run fresh water through the taps before drinking. For the full routine, see our guide to how long do water coolers last, which covers cleaning as part of keeping a unit alive.

When is the thermostat or fan the real culprit?

If the vent is clear, the room is warm, and the control is at a normal setting, the thermostat or fan is failing. Those are the parts to inspect next, and both are service jobs.

A thermostat that reads cold all the time keeps the compressor on. A fan that has stopped or slowed leaves one side of the tank too cold.

You can hear a fan with the cooler running, so listen near the vent before you call anyone.

Replacing a thermostat means opening the refrigeration case and dealing with the wiring. That's work for a technician with the right parts.

Don't try to bypass the control to keep the cooler running, because it removes the only thing that stops the compressor.

If the compressor runs without stopping and the cooler is noisy, the thermostat or a control board is the likely cause. Have it checked before the compressor itself wears out.

Is frozen water safe to drink after a cooler freeze?

No. Drain and clean the cooler first.

A frozen tank can trap stale water, and the freeze and thaw can loosen scale that had been stuck to the liner.

Ice sitting in a warm tank is a good place for bacteria to grow. Once the cooler is running again, the water should be treated as fresh only after a full clean of the tank and lines.

Clean the dispenser taps too, not just the tank. Run cleaner or a diluted solution through each tap following the cleaner's directions, then flush with fresh water until there's no aftertaste.

Can a cold room make a water cooler freeze?

Yes. A cooler in an unheated room near or below freezing can ice up even when its parts work.

Many units have a low-temperature cut-off, but the room still decides how cold the tank gets.

Move the cooler to a heated room when the weather turns. Keep it off outside walls and away from windows that get cold at night.

If you must leave it in a cold space, switch cooling off and drain the tank so it can't freeze solid.

Cold rooms also change how the unit runs. Power use climbs when the compressor runs longer in a cold spot, which our look at water cooler power consumption explains in more detail.

If you're still deciding what type of unit fits your space, our overview of what are water coolers covers the main styles.

How do you stop a cooler freezing up again?

Set the control to the middle, keep the vent clear, place the unit in a heated room, and clean the tank on a schedule. If the tank still freezes after those steps, the thermostat needs a technician.

A regular clean does more than keep water tasting fresh. Scale and film on the liner make the cooling surface work harder, so the unit runs longer and drifts closer to freezing.

Clean every few months, and straight away after a freeze.

Run the checks in order: vent and fan first, then the cold control and room temperature, then the thermostat. Most freezing coolers stop icing once the airflow and setting are corrected, and the ones that don't are usually a thermostat job.

Fix the cause before you keep using the cooler, because a tank left frozen can fail in ways that cost more than the repair.

Frequently asked questions

Why is my water cooler freezing up?

Most often the thermostat has failed closed and keeps the compressor running, or the vent and fan are blocked so cold air collects in one spot. A cold control turned too high and a fridge-style cooler used as a fridge are the other common causes.

Can I just turn the thermostat down and keep using it?

Only after you find the cause. If the thermostat is stuck, turning the dial changes nothing and the tank will freeze again.

Fix or replace the control first, and keep the cooler switched off until the tank no longer ices over.

How do I stop a water cooler from freezing in a cold room?

Keep it in a room above about 50°F (10°C) and away from windows and outside walls. Many coolers have a low-temperature cut-off, but a very cold room can still chill the tank enough to freeze the water inside.

When should I call a technician instead of fixing it myself?

Call service for a thermostat replacement, a compressor that runs without stopping, or any leak or wiring damage. Unplug the cooler first and don't open the sealed refrigeration parts, which need refrigerant handling and proper tools.