Wasps And Mud Daubers Pose A Serious Threat To The Water Heater On Your RV. They Can Enter Through The Water Heater Vents And Cause Serious Damage By Building Nests That Interfere With Air Flow. Camco (Model WH 400) Flying Insect Water Heater RV Screen Fits Suburban Flush Mount 6 Gallon Water Heater Vents. This Easy To Install Screen Will Help Ensure That Your Vent Stays Free From Costly Invasion By Unwanted Pests.