Water dispensers fall into two fundamentally different categories, and understanding which type you have (or are considering) explains a lot about how it actually functions.
Bottled (Top-Loading) Dispensers
These work on simple physics — no pump required. A large water bottle is placed upside-down on top of the unit, mouth-down into a receiving port. As water flows out of the bottle and into the reservoir below, air is let back into the bottle through the same opening, equalizing pressure. A valve at the reservoir prevents overflow: once the reservoir is full, the air/water exchange stops, holding the remaining water in reserve in the bottle until you dispense some and the cycle repeats.
When you press the tap or lever, water flows from the reservoir out through the spout, drawing more water down from the bottle to refill the reservoir as needed.
Point-of-Use (Plumbed-In) Dispensers
These connect directly to your home’s water line rather than relying on replaceable bottles. Water flows in on demand rather than being stored in a large reservoir, which is why these units don’t need bottle replacement — some include a smaller internal tank for temperature-controlled water, while others heat or cool water as it passes through.
Temperature Control
Both types typically offer hot and cold options, achieved through two separate mechanisms:
- Heating: An electric heating element (often a metal coil) heats water in a small internal tank, regulated by a thermostat that cycles on and off to maintain the set temperature.
- Cooling: Most units use either compressor-based refrigeration (similar to a small refrigerator, using refrigerant gas that’s compressed and expanded through coils around the cold water reservoir) or thermoelectric cooling (using the Peltier effect — an electric current creating a temperature difference across two materials, which is generally quieter and better suited to smaller units).
Filtration
Many dispensers, especially point-of-use models, include multi-stage filtration — commonly activated carbon to address chlorine taste and odor, sometimes paired with a sediment filter to catch particulates before they reach the tank. Bottled dispensers rely on whatever filtration (if any) was applied to the water before bottling, since the dispenser itself typically doesn’t filter.
Keeping It Sanitary
Because water sits in an internal reservoir or tank rather than flowing straight through, periodic cleaning matters for either type — this is true whether it’s a simple bottled cooler or a more complex point-of-use system. Regular cleaning of the reservoir, spout, and any removable components helps prevent buildup or microbial growth over time (see our guide on cleaning a Brita water dispenser for a cleaning process that applies broadly across dispenser types).
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