RV Water System ComponentsMost modern RV water systems use a plastic water storage tank of between 20 to 50 gallons of potable water with a hose leading to an electrical demand type water pump. The tank is normally equipped with a valve or plug to allow the tank to be completely drained for winterizing.
The operation of the demand type water pump is automatically controlled by a pressure sensitive switch that shuts off the pump when the system pressure reaches a preset limit. When a tap is turned on, the resulting water flow reduces the system pressure causing the pressure switch to turn on the pump thereby maintaining the system water pressure. When the tap is turned off, the pump continues to run for a few seconds until the system pressure is built up to the preset limit, whereupon the pressure switch again turns the pump off. All components located beyond the demand pump are part of the pressure side of the water system.
In most recreational vehicles, immediately after the water pump, is the "city" water inlet which is a connection to allow the system to use the water and pressure from an external water source. (i.e. the faucets supplied in an RV park etc.)
The pressure side of the water system consists of the various distribution lines, the hot water heater (if so equipped) and the terminal points of the system. (Sinks, shower, toilet etc.)
Beyond these points is the waste water removal system - all of which must be protected from freezing and the resulting damages, as will be described later.
In some RV's, especially older models, an air compressor takes the place of a pump - the compressor forces air into an air tight water storage tank and it is this air pressure that forces water through the lines whenever a tap is opened.