I use the ResMed S9 BiPap machine and it is awesome. It is so quiet, my wife's breathing is louder, heated hose, and it automatically turns on and off. The water tank is small but is good for two days. When you need to clean the tank, it comes aprt in two pieces and is really quick and easy to clean. I always use distilled water.
Here is the water tank / humidifier
http://www.cpapmachinescanada.net/cp...ite-s9-h5i.php