How Does a Water Cooler Work? A Step-by-Step Look Inside

Your cooler gurgles when you fill a glass. It hums, then goes quiet, then hums again, and the back panel feels warm. Many people never get the mechanics of it, and they ask: How does a water cooler work?

A water cooler holds water in one or two small insulated tanks, chills one tank with a refrigeration system or a thermoelectric chip, and heats the other with an electric element. The water comes from a 5-gallon bottle or from the building’s water line, and each tap draws from its own tank. Water cooler and water dispenser mean the same thing.

In this guide, we tell you how water gets in, cooling, hot water, parts, sounds, power, and FAQs.

How Do Water Coolers Work?

The steps of how a water cooler works are simple: Every cooler or dispenser follows the same path, whatever the brand:

1. Water comes in, either from a bottle or from a water line.
2. It fills a cold tank, and in hot-and-cold models, a second, smaller tank.
3. The cold tank is chilled. The small tank is warmed by a heating element, and a thermostat keeps it at its set temperature.
4. When you press a tap, water leaves the tank that tap is connected to.
5. The tank refills from the supply, and the cycle repeats.

How Water Gets Into a Bottled vs. Bottleless Water Cooler

A hot and cold water dispenser gets its water in one of 3 ways:

Top-Load Bottled Coolers

On a top-load cooler, you turn a water bottle upside down and set it on the top. A short probe opens the bottle, and the water flows down into the cold tank because of gravity. As water leaves the bottle, air slips in to take its place, which is the bubble you see. You need to get 5-gallon jugs that are made to fit most standard top-load floor-standing water cooler models.

Bottom-Load Bottled Coolers

A bottom-load cooler keeps the bottle in a cabinet at the base, so there is no overhead lift. A tube runs from the bottle’s cap to the bottom of the bottle, and a small pump lifts the water up to the tanks. That pump needs power, so after you put in a new bottle, you may hear it run for a few minutes while the tanks fill.

Bottleless (Point-of-Use) Coolers

A non-filtered or filtered bottleless cooler connects to a cold water line, which the ENERGY STAR water cooler specification calls a pressurized water source (ENERGY STAR specification). It runs the water through filters before it reaches the tanks. Both floor coolers and our water counter-top coolers work this way, and our team sets them up. Cooler and bottle sizes vary by model, so the office water cooler size is worth checking before you choose.

How does a Water Cooler Make Water Cold?

A cooler chills its cold tank in one of two ways, and in both the heat does not vanish. It moves out into the room. Most coolers hold cold water at about 40°F to 50°F.

Compressor Cooling (the Same Idea as a Refrigerator)

Most full-size coolers chill water the way a refrigerator does. The loop has 4 steps:

1. A compressor squeezes a refrigerant gas, which makes it hot.
2. The hot gas travels through coils, usually at the back, and gives its heat to the room. As it cools, it turns to liquid.
3. The liquid passes through a very narrow tube, where the pressure drops and it turns cold.
4. Coils wrapped around the cold tank, called the evaporator, take heat out of the water. The refrigerant then goes back to the compressor, and the loop starts again.

The heat is not destroyed. It moves from the water into the room, which is why the back of a working cooler feels warm. The refrigerant is sealed in, and only a certified technician should service it (EPA).

Thermoelectric Cooling (the Peltier Effect)

Smaller counter-top coolers often use a thermoelectric chip instead. It is a flat chip made of semiconductor material (US Department of Energy). When electricity passes through it, one face turns cold, and the other turns hot, which is called the Peltier effect. The cold face touches the tank. The hot face is attached to a metal heat sink, and a small fan blows the heat away. There is no refrigerant and no compressor, so these units tend to be quiet, but they can have a harder time in a warm room.

How does a Water Cooler Heat Water?

A hot-and-cold cooler has a second, smaller tank with an electric heating element, a little like a tiny water heater. A thermostat turns the element on and off to hold the water at its set temperature. That temperature is high, often between about 165°F and 200°F depending on the model, but it stays below boiling, which is 212°F at sea level. Because the tank is small, heavy use pulls in cooler water that needs time to reheat. A cold-only cooler skips this tank, so it has no hot tap.

Why Hot and Cold Water Stay Separate

The cold tank and the hot tank are separate, and each tap draws from its own tank. That is why one cooler can give you both a cold glass and a hot cup, and why the two do not mix at the tap. Both tanks refill from the same supply.

Hot Water Safety

The hot tap on a cooler runs hotter than the water from a home faucet, which is best kept at or below 120°F. Water at 140°F can cause a serious burn in a few seconds, and water at 160°F can do it in about one second (UTMB Department of Pediatrics). For that reason, many hot-and-cold coolers have a child safety lock on the hot tap, though not every model has one. Check that yours has a lock, keep it on, and place the cooler where young children cannot reach the taps.