Some of the high-end dental equipment:
"I absolutely LOVE this machine. My mouth feels so clean after use, and it truly is amazing the stuff that still comes out after brushing and flossing (although flossing seems unecessary if using this machine).
It definitely says in the instructions to empty it after every use, and to unplug the unit, so don't pay attention to reviewers who say the reservoir leaks, especially if they are leaving water sitting in it after use (which is kind of gross--the idea of using water that's been sitting for hours to clean your mouth????). I can't imagine not using up the water anyway, it only takes about 2 minutes---the recommended time to brush your teeth, so I can do 2 minutes for each to get teeth THIS clean.
And you can always just put less water in. The reservoir is very easily lifted up so that you can run water into it, and dump out any left.
So, for the test, I used Listerine Smart Rinse after brushing and flossing; this particular product "shows" leftover plaque by clinging to it and helping to remove any left in your mouth---it turns color so that you see clear rinse with tiny colored liquid---supposedly the plaque. I originally thought the rinse didn't work, because it ALWAYS had colored particles when I spit out after brushing and flossing, no matter how careful and thorough I was. Well, after using the waterpik the first time, I tried the Listerine rinse again----not a single bit of colored liquid pieces, all of it was clear---proving to me that not only did the waterpik get at all the gunk in my mouth, but the rinse really did work. I won't really need it anymore (I originally bought if for my kids---they didn't ever use it, so I was just using it till it was gone) since I know the Waterpik gets it all so clean!!!!
As for how long it lasts---I don't know. But it has a 2 year warranty, and I would definitely buy another if I had to in 2 years."