RV Hot Water Heater Bypass Valve and Drain Valve

Last updated on September 20th, 2021 at 05:00 pm. Originally published on May 10th, 2015


The worst kind of repair is the preventable kind. Be very thorough when winterizing your RV.

RV-Antifreeze in Sink

There really is no need to put anti-freeze in the hot water heater, fresh water holding tank, grey and black water tanks, as they are drained, and large enough to expand and contract without any damage occurring.

The water lines in an RV are usually very thin and have little room to expand. They need RV anti-freeze.

The RV water heater has a water line at the bottom where the cold water goes in. On top of that line, there is a hot water line that feeds your pipes. If there is a middle pipe that connects these two lines, congratulations, you have just located the RV’s bypass valve.

Water Heater Bypass

A bypass prevents anti-freeze from going into the heater. If for some reason anti-freeze does enter the heater, you will need to flush it out completely before you can store more water for showering. Most RVs have this bypass installed. Some RVs have one, two, or three bypass valves.

  • Three-valve system
    Ensure that the valves on the cold and hot water line are turned perpendicular to the line. Turn the bypass valve in such a way that it is parallel to the line. The anti-freeze will now pass straight through the line bypassing the tanks.
  • Two-valve system
    Turn both valves so that they lie parallel to the line. This will allow the water to bypass the heater.
2 valve Water Heater-Bypass
  • One-valve system.                                                                                                                                                                                                    Simply turn the valve perpendicular to the line on a one-valve system to bypass the hot water tank.

You should also bypass your filter, or remove it, before you pour anti-freeze in the system.

The winterization process can be a baffling practice for a new RV owner. It varies slightly depending on the model of the vehicle, but certain aspects are standard in all RVs. One such practice is the water heater bypass.

RV hot water heater bypass valve

Some water heaters come with a bypass valve installed which makes things super easy. If your RV does not have one, have it installed.

  • Find your heater. It is located on the outside of your van and is most likely located behind a large cover, with a screen on the upper right-hand side.
  • Open the screen. Behind it, you will find an anode that is usually removed when draining the tank for winterization. The anode gets loose with age, so replace it when it starts to look aged. You will need a 1- 1/16 socket for the anode rod.
  • Now go into your RV and find the heater from the inside. You may need to remove a cover to access it.
  • Cold water comes in at the bottom and hot water comes out of the top of the heater. If your RV has a bypass valve, these two pipes will be connected directly to each other using a third pipe.
  • The lever of the valve should point in the direction that you want the water to flow. If it is turned 90 degree towards the bypass line, it will flow into the bypass line and not enter the tank.
  • Both valves on the hot and cold water line should be turned to prevent anti-freeze from entering the hot water tank.
  • Remove the fuse of your heater to prevent it from going on while no water is in it.

There is more to winterizing than simply bypassing the hot water system. Install a bypass valve if your RV does not have one, to make winterization easy.

RV hot water heater check valve

Check valves

The check valve line is where the RV and the city water first meet. This needs some anti-freeze too. Your water pump should be off before adding the anti-freeze.

• Remove the screen that’s attached to the water hook-up. The check valve is inside this.
• Push the valve in until all the water in it comes out and anti-freeze starts to dribble out.
• Reconnect your water pump.

Remember, if anything sounds too complicated to do, don’t do it. Take your RV to a service department.

Thanks for reading and don’t forget to comment below!

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