This hard water filter is designed to be used in the Oreck VersaVac. This kit includes 1 water filter. Depending on hard water conditions in your area or how often you use the steam function on the VersaVac, the water filter should be replaced every 12 months. Minerals that form hard water will reduce the life of the water filter and will eventually allow deposits to build up in the heater of your VersaVac, diminishing its performance. While the Versavac will work using plain tap water, Oreck recommends using distilled or de-mineralized water in your VersaVac to prolong the life of its filter and heater.