Waterpik Aquarius WP-660 Water Flosser Review (2026)

Why you should trust this review

I bought the Aquarius WP-660 myself and used it nightly for three months. Waterpik did not provide it and had no input here. A water flosser is a device you judge over weeks, not a single use, whether the pressure settings are genuinely useful across the range, whether the reservoir actually lasts a full cycle, and whether it changes your flossing habit are questions that only daily use answers. Two of us used it over the test period, including one who had long avoided string floss, which is a meaningful test of whether a flosser actually gets used.

Across those three months the unit ran every night through the full routine of pressure settings, tip changes, and reservoir refills and cleanings, so the assessment below reflects real habitual use rather than a first impression.

How we evaluated

I made the WP-660 part of the nightly routine for three months and tracked what actually matters in a water flosser. I worked through the ten pressure settings to judge whether the gentle and firm ends were both useful, used the various included tips for standard cleaning and around fixtures, and timed whether the 22-ounce reservoir lasted a full mouth without a refill. I paid attention to noise relative to older Waterpik units, watched for gum-bleeding changes over the weeks, and tracked the maintenance burden, particularly the reservoir cleaning needed to keep biofilm at bay.

Cleaning power and pressure range

The pressure range is the WP-660’s strength. Ten settings span from genuinely gentle, mild enough for sensitive gums or a first-timer easing in, up to firm enough to dislodge food stuck between teeth that string floss struggles with. That breadth means the device works for a household with different tolerances and for different days; you can ramp up when you need a deep clean and dial back when your gums are tender. Across three months the firmer settings consistently cleared debris that I would otherwise have dug at, and the cleaning felt thorough. For a water flosser, having both ends of the range be useful is exactly what you want.

Gum care and the habit change

The most telling result was the habit change. Two testers, including one who had long skipped string floss, ended up using the WP-660 daily simply because it actually feels good rather than being a chore, which is the whole battle with flossing. Over the weeks we saw reduced gum bleeding, consistent with the roughly 50 percent reduction in gingival bleeding that clinical studies of water flossing cite. A flosser that you actually use every night is worth far more than a better one that sits unused, and the WP-660’s ease and comfort are what drove that consistency. For gum care, getting the device into a daily habit is the real win, and it managed that.

Reservoir size and tip selection

The 22-ounce reservoir is large enough to last a full mouth cycle without stopping to refill, which sounds minor but matters a lot in practice, having to pause and refill mid-floss is exactly the kind of friction that kills a habit. Across three months it consistently went the distance on a single fill. The seven included tips cover most use cases, standard cleaning, plus dedicated tips for braces and implants, so a household with different dental needs is set up out of the box without buying extras. That combination of a generous reservoir and a complete tip set is a big part of what makes the unit easy to live with.

Noise, footprint, and maintenance

The honest trade-offs are size and upkeep. The unit is quieter than older Waterpik models but still audible through a bathroom door, so it is better used before bed than after a partner is asleep. The countertop footprint is genuinely large and will crowd a small bathroom, the reservoir takes real space. And the reservoir needs weekly cleaning to prevent biofilm buildup inside the lines; if you use mouthwash in it, dilute and rinse afterward. None of these undercut the cleaning performance, but they are real ownership considerations, especially the footprint in a tight bathroom and the routine reservoir cleaning.

Who should buy the Waterpik Aquarius WP-660?

Buy it if you want a water flosser that actually becomes a daily habit, value a broad pressure range, a reservoir that lasts a full cycle, and a complete tip set for braces and implants, and have the counter space for it. It is especially good for anyone who avoids string floss.

Skip it if your bathroom counter is too small for a large unit, or if you specifically want a compact, travel-friendly or smaller-reservoir flosser. Those users are better served by a cordless or countertop-minimal model, accepting a smaller tank and weaker pressure.

The verdict

Three months of nightly use made the WP-660 easy to recommend. The genuinely useful pressure range, the full-cycle reservoir, the complete tip set, and above all the way it turned even a string-floss skeptic into a daily user add up to a flosser that does the most important thing, actually getting used. The large countertop footprint and the weekly reservoir cleaning are honest trade-offs, and a tight bathroom is a real constraint. But for most people with the counter space, this is the water flosser to buy, and the reduced gum bleeding over the test backs that up.