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Here is a guide on ensuring your motorhome, RV, or caravan water heater is full, considering the bypass valves, drain valves, and temperature-controlled emergency drain valves.
To know when your motorhome, RV, or caravan water heater is filled with water, first, if you have bypass valves check that they are not bypassing the heater. Secondly, check that your drain valves are closed. And last, turn on a water tap on hot water until continuous water flows and no air is coming out.
So it sounds easy to ensure your water heater is full, right? If the settings are set correctly, you need to turn on the hot water until you have continuous water flow in the tap. But maybe you have a bypass valve that bypasses the water heater, or maybe you never get a continuous water flow because an emergency drain valve or drain valve is open.
I have made diagrams making it clear to you how this works in this article.
The reason why it is so essential to ensure your water heater is full before you turn it on is that some water heaters get damaged and destroyed if turned on while they are empty, so it could be an expensive mistake if not done correctly.
1. Make Sure Your Water Heater Is Not Bypassed
To ensure your motorhome, RV, or caravan water heater is not bypassed, check how the bypass valves are set. They should be located near the water heater and easily accessible if you have them.
When the handle of the bypass valve goes in the same direction as the water pipe, the water can flow through there. When the handle of the valve is located like a cross with the water pipe, the water can’t flow through the water pipe, as you can see in the image above and below.
In the picture above, you can see how the bypass valves should be set when the water heater is in use and you want to fill up the water heater with water.
2. Make Sure The Drain Valves Are Closed
The diagram above shows that the drain valves are closed, and the water will flow through the water heater and continue to your water taps and shower. If the drain valves are open when you turn on the water tap like in the diagram below, you will only pump water outside of your motorhome, RV, or caravan, and you will not fill up your water heater, nor will you get any water coming out from the taps.
The water heater and cold water pipe drain valve are also expected to have an emergency freeze protection valve, which automatically opens when the temperature gets close to freezing. What this helps you with is to ensure the water heater never can freeze, even if you forget to drain your water heater before the winter.
Start Warm Water From The Tap
Now when you have made sure that your bypass valves are not bypassing the water heater if you have bypass valves and checked that your drain valves are closed, you can start pouring hot water from the water tap or shower and wait until you get a nice continuous flow without any air in it.
This usually goes fast, not even a minute, with a small water heater, but if you have a big water heater, it will take longer to fill up. Here is an example of me filling up my water heater.
When you have continuous water flow on warm water, your water heater is filled up, and you can start the water heater without damaging it. Notice that since you don’t have your warm water heater on when you fill it up, there won’t be warm water from the tap.
I don’t have any bypass valves, and this is how the water connections look around my water heater:
Since you should always drain your RV water heater if you are not going to use your RV within 2 weeks, I suggest you check out this video where I show you how to do that too! Or, if you prefer, you can read this article about it.