RV Water Systems

RV’s have 2 water systems, city water and onboard (potable) water. Some components are shared between the 2 systems and others are separate.

1. City Water: City water should be used any time there is a water faucet available within a reasonable distance. Using city water, there will be a constant water supply without using the RV’s water pump. The city water system is the system that uses a water hose attached to a faucet. The faucet supplies the water and pressure for the RV. There is a connector on the RV that will connect to a water hose. Some RV’s use identical connectors for the city water and the potable water fill. Some RV’s use a water hose connector for city water and a fill tube with a cap or door enclosing it. Some RV’s use the same connector for city water and potable water fill, and use valves to switch between them. In any case, they should be labeled. An RV “drinking” water hose should be used for both city water use and fresh water tank filling.
 

Behind the walls, the water lines from the city water and potable water are teed together. Connecting the lines together in the plumbing system with a tee, allows all components to be shared. There are check valves located in the water hose connectors or in the tee so water will not feed back from 1 system to the other. 

2. Potable Water: Potable water is the water that is stored in the RV’s fresh water tank. The potable water system should be used any time a water faucet connection is not convenient or available. A water pump must be used to pump water from the tank to the plumbing system. This pump will have a switch located somewhere in the RV that must be turned on to operate. The water is limited to the amount in the fresh water tank. There is usually a gauge located in the monitor panel to indicate water tank level. RV’s built after the early to mid 1970’s use a demand pump. This type of pump runs only as water is demanded. In other words it runs when any water outlet is opened. A demand pump uses a pressure switch to cycle off and on. When the pump is on, there will be pressure in the system. Once the preset pressure is achieved, the pump will automatically turn off. When a water outlet is opened and pressure drops, the pump will turn on to build pressure again. This cycle will continue each time a water outlet is opened. There are 2 exceptions when the pump will continue to run and must be turned off at the switch.  If the water supply is empty, the pump will continue to run since it cannot build pressure. If there is a water leak, the pump will continue to run. I sometimes use the water pump as a leak indicator. If a pump cycles on and off with all water outlets closed, there is a leak somewhere in the plumbing.

RV Help Desk Recommendations:

Do not drink the water. Due to the possibility of bacteria in the RV’s water system, I recommend not drinking the water. Many times the water supply integrity is unknown. Always take safe drinking water with you.

Carry plenty of drinking water hose with you. Hoses are available in a variety of lengths. I usually take several 25 foot hoses. 25 feet is easy to deal with, but may not always be enough.

Carry extra water hose washers with you. Sometimes they fall out of the hoses. Cheap item to carry saves a lot of aggravation.

While this seems like a “no brainer” to me. I see it all the time. Do not store the drinking water hose in the same compartment as the sewage dump hose. (Bacteria transfer)

Due to the inherent design of the RV water system, there may be frequent flow problems from faucets. Aerator screens can clog easily due to debris “breaking” loose. This is often caused from air “hammer”. Connection/Disconnection from city water supply, water pump cycling, and running out of fresh water all cause air in the water supply. Air in the lines can cause a hammering condition. This hammering condition often breaks loose debris in the lines or faucets. The debris goes right to the outlet, but is stopped by the aerator screen. If the flow is restricted, remove the aerator, clean or replace the screen and reassemble.

Have a question about this rv education article  or is there is a topic you would like to see an RV Education article on? 
Please visit our RV Forum and post your question or request