DO NOT BUY WATERPIK. I used their product sold at Costco that came with a plug in unit and a battery powered portable unit.
I used the plug in unit for about 3 months and then I used it as normal (pretty low setting on the pressure as always) and the pressure suddenly went on full blas! It ripped my gum up and I bled for a week. I called the company and they said to return it for analysis and they would refund the money and further told me I could go ahead and keep the hand held battery unit. I sent it back and I have not received a refund.
I called, the original person that I spoke with, her name is Joan 800-525-24774 (her number 970-484-1352) and she said they are refunding me for only the plug in unit because I didn't return the battery unit!
OW, I should have gotten an attorney and sued them for pain and suffering! What nerve, what a liar!