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How does a water flosser work?

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In short

A water flosser uses a small electric pump to push water from a reservoir through a hose and out of a narrow tip in rapid pulses. You aim the stream between the teeth and along the gumline. A dial or buttons set the pressure, and the tip shapes the jet. Countertop models run from the mains with a large reservoir; cordless models have a built-in battery and a smaller tank.

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Water flossers, often called by the brand name Waterpik, are an alternative or addition to string floss and interdental brushes. They look simple from the outside, but there is a pump, a valve, a pressure control and a selection of tips doing the work. This guide explains what happens between filling the reservoir and the water leaving the tip, what pulses and pressure figures mean, and how countertop and cordless designs differ. For advice on cleaning between your teeth, the NHS recommends speaking to your dentist or hygienist.

Inside a water flosser

A countertop flosser has a reservoir that sits on a base. Inside the base is an electric motor driving a small piston pump. Water flows from the reservoir through a one-way valve into the pump, which pushes it in short bursts through a hose to the handle. The handle has a tip, a button to release the tip and usually a pause switch.

A cordless flosser packs the same parts into one unit: a tank at the bottom or back, a battery-powered pump and a tip on top.

Reservoir (ml)Pressure dialPumpHosePause buttonRotating tip
A countertop water flosser: the pump draws water from the reservoir and sends it up the hose to the tip.

Pulses and pressure

The water comes out in pulses rather than a steady stream. Waterpik quotes around 1,200 pulses per minute on many of its countertop models. The pulsing is part of the design, and the maker describes it as helping to clean between teeth and below the gumline.

Pressure is measured in pounds per square inch (psi). Countertop Waterpik models typically offer a wide range of settings from low to high, adjusted with a dial. Starting low and increasing over time is the usual advice, as high pressure can feel strong at first.

TermWhat it means
Pulses per minuteHow many bursts of water the pump delivers each minute
Pressure (psi)How hard the water is pushed out; set with a dial or buttons
Reservoir (ml)How much water the tank holds, which sets how long a session lasts
TipThe nozzle; different shapes suit different needs
Pause switchStops flow on the handle without turning off the motor
Key water flosser terms

Countertop and cordless designs

Countertop flossers have larger reservoirs and more pressure settings, and they run from the mains so there is no battery to charge. They take up space beside the basin and need a socket, which in UK bathrooms can be a problem. Cordless flossers are smaller, charge like a toothbrush and suit travel or bathrooms without a suitable socket, but the tank usually needs refilling during a session.

Combination units such as the Waterpik Sonic-Fusion add a sonic toothbrush to a countertop flosser, with water coming through the brush head. Our sonic toothbrush guide includes the Sonic-Fusion 2.0.

  • Countertop: larger tank, more settings, needs a mains socket
  • Cordless: compact, rechargeable, smaller tank
  • Combo: brush and flosser in one, countertop base

Tips and what they do

Most flossers come with several tips. A standard jet tip is used for general flossing. Other tips, according to Waterpik, are designed for braces, implants, crowns or periodontal pockets. Tips wear and should be replaced at the interval in the manual.

If you have braces, implants or gum problems, ask your dentist or hygienist which tip and pressure setting to use.

Note:Water flossers combine water and mains electricity. Keep the base dry, unplug before cleaning, and never use a countertop unit near a bath or shower. Use lukewarm, not hot, water.

Using a water flosser

The basic routine is simple, though it takes a few sessions to avoid splashing.

  1. 1

    Fill the reservoir with lukewarm water and seat it on the base.

  2. 2

    Choose a tip and click it into the handle.

  3. 3

    Set the lowest pressure to start.

  4. 4

    Lean over the basin, put the tip in your mouth and close your lips enough to stop splashing.

  5. 5

    Switch on and guide the tip along the gumline, pausing briefly between each tooth.

  6. 6

    Let the water drain into the basin as you go, then empty the reservoir.

Where a water flosser fits in

The NHS advises cleaning between your teeth, using floss or interdental brushes, and your dentist or hygienist can advise which method suits you. A water flosser is designed to clean between teeth; it is not a replacement for brushing twice a day with fluoride toothpaste. Our guides on water flosser vs string floss and whether a water flosser is worth it cover the decision, and our best electric toothbrush guide covers the brushing side.

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Frequently asked questions

How does a Waterpik work? An electric pump pushes water from a reservoir through a hose and tip in rapid pulses, with a dial to set pressure.

What pressure should I use? Start at the lowest setting and increase gradually. Ask your dentist or hygienist if you are unsure.

Can I put mouthwash in a water flosser? Some makers allow diluted mouthwash and some advise against additives. Check your manual.

Does a water flosser replace brushing? No. It cleans between the teeth. Keep brushing twice a day with fluoride toothpaste, as the NHS advises.

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