How to use a water flosser properly: pressure, order and settings

Oral Cove editorial deskUpdated September 2026Dental claims checked against ADA, NHS and Cochrane sources
Short answer

Fill with lukewarm water. Start on the lowest pressure setting. Put the tip in your mouth before switching on, aim the jet at 90 degrees to the gumline, and work from the back teeth forward, pausing briefly between each tooth. One minute, once a day, before you brush.

Most water flossers arrive with a one-page manual and a lot of marketing. The settings that decide whether it works and whether it hurts are in the manual, and the evidence about what it can achieve is in a Cochrane review most listings never mention.

On this page
  1. The settings, one at a time
  2. The order the evidence supports
  3. Finding your pressure
  4. Not getting soaked
  5. What a water flosser does not do
  6. Questions people ask

The settings, one at a time

Water flossers differ in shape, but the settings that matter are the same five on every model. These are the values the manufacturer instructions specify and the values the clinical trials used.

Setting What to use Why that value
Water Lukewarm tap water The manuals say lukewarm, and the irrigation trials used plain water with no additive.
First-week pressure The lowest setting on the dial, usually 1 of 10 Waterpik instructions say to set the lowest pressure for first-time use and raise it gradually.
Working pressure The highest setting that stays comfortable across the whole mouth A 2025 trial ran at dial setting 8 of 10 and found no more gingival abrasion than an interdental brush, so strength itself is not the danger. Comfort is the limit.
Tip General tip daily, orthodontic tip around brackets, plaque-seeker tip around implants The tip decides where the jet reaches more than how hard it hits.
Timer Use the 30-second pause to switch arches and stop at around one minute One minute is the recommended cleaning time for the reference device.

The order the evidence supports

The American Dental Association says brushing and cleaning between the teeth can happen in either order as long as the cleaning is thorough. The NHS is more specific and recommends cleaning between the teeth before brushing. A randomised crossover study in 25 dental students compared string floss before versus after brushing. Flossing first reduced interdental plaque more (p = 0.001) and left more fluoride in the interdental plaque (p = 0.027) than brushing first. It did not test a water flosser, so it does not establish that one water-flosser sequence is superior.

Cleaning between the teeth before brushing is a practical routine consistent with the NHS advice. The small string-floss trial is supporting context, not direct evidence for water-flosser timing.

  1. Clean between the teeth first. Water flosser, string floss or an interdental brush, once a day, before you pick up the toothbrush.
  2. Brush for two minutes with fluoride toothpaste. The NHS puts the adult strength at 1,350 ppm fluoride or more, last thing at night and one other time.
  3. Spit, do not rinse. Rinsing with water straight after brushing washes away the fluoride that is still sitting on the teeth. The NHS also advises using mouthwash at a different time, such as after lunch, rather than straight after brushing.
One interdental session a day, not threeThe ADA recommends brushing twice a day and cleaning between the teeth once a day, and it warns against reusing floss or a device. If you water floss morning and night, the second session is optional.

Where a water flosser sits relative to string floss is a separate question, and it depends on the outcome you measure. We set the trials side by side in water flosser versus string floss.

Finding your pressure

  1. Use the lowest dial position for the first three or four days. This is what the manual asks, and it teaches your hands where the jet points.
  2. Move up one step every few days while the whole mouth stays comfortable.
  3. Step back down if you see any of these: stinging on one tooth, gums that ache for more than a few minutes afterwards, a jet that makes you flinch, or bleeding that gets worse session on session.
  4. Keep the tip at roughly 90 degrees to the gumline, as the instructions describe. Angling it along the tooth sends water where it does less and splashes more.
  5. If you have periodontal pockets, do not aim into them yourself. Makers sell a soft pocket tip for that, to be used at the lowest pressure after a clinician has shown you how.
When to stop and book an appointmentCleaning between the teeth should reduce bleeding over one to two weeks. If your gums still bleed after two weeks of daily cleaning, if a tooth feels loose, or if you have swelling, a bad taste or pain when biting, that is a dental appointment, not a settings problem. A water flosser cleans surfaces. It does not treat an infection, and it does not replace a check-up.

Not getting soaked

Splashing is nearly always technique, not the machine. Three fixes, all from the instruction manuals:

  1. Put the tip in your mouth before switching the water on, and switch it off before taking the tip out.
  2. Lean over the sink with your lips nearly closed, just open enough for water to run out. That gap is the whole trick.
  3. Start at the back teeth and work forward. The first burst always lands somewhere unexpected.

What a water flosser does not do

It does not replace brushing, and the evidence for it is thinner than the marketing implies. The 2019 Cochrane review pooled 35 randomised trials with 3,929 adults. Its findings on oral irrigators, which is what a water flosser is:

Outcome What the review found for oral irrigators plus toothbrushing
Gingivitis at one month May reduce it, on very low certainty evidence from 4 trials and 380 participants
Gingivitis at three and six months No effect shown
Bleeding sites No advantage over toothbrushing alone
Plaque No advantage over toothbrushing alone

The same review rated interdental brushes as having the stronger record, and warned that most participants started with low levels of gum inflammation, so the effect sizes may not matter much to a real person.

None of that makes a water flosser a bad purchase. It makes it an option rather than an upgrade, and it means the decision should rest on what you will actually do every day. If floss and interdental brushes work for you, they still carry the better evidence. If braces, implants, crowns or awkward hands make them impractical, the water flosser evidence is more favourable, and the routine builder works out which situation you are in.

Where the rest of this is covered

Questions people ask

Should I use a water flosser before or after brushing?
Before brushing is a practical routine consistent with NHS advice, while the ADA says either order can work when cleaning is thorough. The small sequence trial discussed here used string floss, not a water flosser. After brushing, spit without rinsing; use mouthwash at a different time unless your dental professional gives different instructions.
Why do some dentists not recommend water flossers?
Usually it is a comment about evidence, not safety. Cochrane 2019 called the oral irrigator evidence limited and inconsistent, and found interdental brushes had the stronger record for plaque and gingivitis. Waterpik water flossers do hold the ADA Seal in the powered interdental cleaner category, so the objection is about which tool cleans best, not about harm.
Do you keep your mouth closed when using a water flosser?
Nearly. The instructions say to lean over the sink with lips close enough to stop splashing while letting water run out. Keep the tip in your mouth the whole time, and use the pause switch if you need to swallow.
Do you put tap water in a water flosser?
Yes. Lukewarm tap water is what the manuals specify and what the trials used. Cold water feels sharper on sensitive teeth, and nothing added to the reservoir has been shown to improve gum health.
What are the drawbacks of water flossers?
The device costs more than a box of floss, the tips are a running cost, cordless units need charging and often a refill, water lands on the mirror while you learn, and Cochrane found no advantage over toothbrushing alone for plaque. The 2025 trial that favoured a water flosser was funded by the manufacturer.
What is the best liquid to add to a water flosser?
Plain lukewarm water. If you want to add mouthwash, read your model manual first, because some makers ask you to rinse the reservoir afterwards and some warn against thick solutions.

Sources

  1. Waterpik. Recommended technique and how to floss with a water flosser (manufacturer instructions) — www.waterpik.com/how-to-floss/
  2. Waterpik WP-600 series instruction manual (pressure setting, tip use, 1-minute timer) — www.waterpik.com/pdfs/WP-600-series-instruction-manual.pdf
  3. American Dental Association. Dental floss and interdental cleaners: key points and the once-a-day recommendation — www.ada.org/resources/ada-library/oral-health-topics/floss
  4. NHS. How to keep your teeth clean: floss before brushing, fluoride strength, do not rinse — www.nhs.uk/live-well/healthy-teeth-and-gums/how-to-keep-your-teeth-clean/
  5. Worthington HV, MacDonald L, Poklepovic Pericic T, et al. Home use of interdental cleaning devices, in addition to toothbrushing. Cochrane Database of Systematic Reviews 2019 — www.cochrane.org/evidence/CD012018_home-use-devices-cleaning-between-teeth-addition-toothbrushing-prevent-and-control-gum-diseases-and
  6. Mancinelli-Lyle D, Van der Weijden GA, Slot DE. Efficacy of a water flosser compared to an interdental brush on gingival bleeding and gingival abrasion: a 4-week randomised controlled trial. International Journal of Dental Hygiene 2025 (funded by Water Pik, Inc.) — pmc.ncbi.nlm.nih.gov/articles/PMC11717974/
  7. Mazhari F, Boskabady M, Moeintaghavi A, Habibi A. The effect of toothbrushing and flossing sequence on interdental plaque reduction and fluoride retention. Journal of Periodontology 2018 — pubmed.ncbi.nlm.nih.gov/29741239/
  8. American Dental Association. ADA Seal of Acceptance, Waterpik cordless water flossers (powered interdental cleaners category) — www.ada.org/resources/research/science/ada-seal-of-acceptance/product-search/a065e000007A372AAC/waterpik-cordless-water-flossers

Water flossers and replacement tips

Portable irrigators, countertop units and the nozzles they take, listed with the pressure range and tip type in each listing.

See water flossers

Which one to buy

Every option this store stocks, with price, type and who it suits, is compared on one page.

Back to blog