Having suffered from periodontitis several times in my life and because I'm lazy with flossing and interdental brushes, I decided to try the water flosser in hopes of avoiding the dentist...
So here we go:
For those who don't know, it's a powerful water pump, and you attach accessories to the end. It's like a water jet on the teeth, so to speak. The theory is not bad.
It promises to clean between the teeth, and it does to some extent. After a year of use, I have to say that unfortunately nothing can replace floss and interdental brushes. It does something, but it's not enough. I notice that after using it, if I floss, something will come out from between my teeth. The reason is that the water goes straight with pressure, but food can get stuck in crevices and it doesn't reach them...
Also, the reason I bought it was for convenience... wrong:
I have to be naked from the waist up, because in the attempt to see where you're aiming with a mirror, the bathroom gets wet and you're a mess... wet, trying to clean mirrors.
At its highest setting of 7 and above, where you feel like something is happening, it causes bleeding and injuries to the gums and subgingival area. This, combined with the mess, creates a bathroom thriller!
I also have the impression that the gums became weaker due to the frequent bleeding it caused. Since I stopped using it, I see improvement again.
We're not talking about something similar to portable battery-operated electric toothbrushes, those don't have enough power, and you have to refill water every 30 seconds.
All of the above, combined with the SHOCKING price, I wouldn't say it's a deal. If it was around 30 euros, I would say it's okay, but at 100 euros, I can't recommend it

I have been using water softening systems daily for over 25 years. This particular product lasted me exactly 4.5 years (June 2013 - December 2017), and what broke was the tube that calcified and was cut by the water salts (a very normal wear and tear). And it has simply become a habit for me. It is truly exceptional and very effective.

The only negative aspect is the price-value ratio: I bought the previous one for 86 euros. Now it is over 100. Either way, I consider it excessive for a simple construction that definitely does not cost the distributor more than 30 euros.

Finally, a note regarding the rechargeable specification: it operates with electricity, it does not have rechargeable batteries.

Review update May 2021: I was forced to buy a new one for the same reason (tube). Price 120 euros!!! And they reduced the motor power by about 30% (what used to be 6 is now 8-9). I will not buy it again. I will prefer the competition because with a similar weak motor, it costs less than 50 euros.

About a month of using this product and I consider it one of the most necessary for complete oral hygiene. It does not replace dental floss as it cleans between the teeth, but it cannot reach where the teeth touch and there the floss is necessary. Correct use: first floss, second water pik, and third toothbrush. Four stars because the product is made of cheap materials and I don't think it will last for a long time (it only has a one-year warranty).

Well, 27.02.2019 UPDATE!!!!
The 4 stars I gave three years ago (when I bought it and first used it) are very few! Its materials are not cheap at all, excellent quality, excellent effectiveness (along with dental floss and regular brushing) in cleaning the spaces between the teeth and under the gums! It is by far the best investment one can make in terms of oral hygiene. Better placement even than an electric toothbrush. I HIGHLY recommend it to EVERYONE, those who take oral hygiene very seriously, whether they have excellent dental and gum health and want to maintain it or are struggling to improve it! CAUTION: always in combination with good, regular brushing and with proper, regular use of dental floss.