The Aprilaire 330 humidifier requires annual maintenance consisting of replacing the humidifier filter (water panel evaporator) and washing out the pad frame and water distribution tray. If you need to replace this model with an entire new unit, this model has been discontinued and replaced with the models 1120, 1130 and 1140. They are also listed on the Aprilaire page. Unfortunately the only parts available for this model are shown below. The solenoid valve is discontinued but you should able to use the 4040 solenoid valve and adapt it on site to function for this application.