MAKE SURE YOU USE IT AT LOW FLOW if you get one. It REALLY gets up in there and cleans things out. Also, you need to make a saline solution with Sea Salt (only!!) and then clean that out of your Water Pik.
This is by far the greatest thing I've ever done for sinus health. After using one and cleaning myself out of the worst infection ever, I've not had another. I've actually not had to use the irrigator for years.