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Everything You Need to Know About Your RV Hot Water Heater Check Valve

The RV hot water heater check valve isn’t the first thing you think about when having issues with RV hot water or maintenance. The RV hot water heater can be convenient when showering or using hot water in the sink, though.

So what does the hot water heater check valve do? Is it valuable to your RV and its water system?

The hot water heater check valve doesn’t always come with the hot water heater, but when installed it attempts to prevent hot water from returning to the hot water heater. There are many reasons for this we will discuss below.

Where is the hot water heater check valve?

The hot water heater check valve is on the same water line that allows water to exit from the hot water heater. This is usually on the back of the hot water heater and often towards the wall of your RV, where the end then goes into the wall of the RV for supply around the RV. 

The check valve doesn’t look especially exciting. It’s more commonly a brass or bronze fitting with two screw ends.

What does the hot water heater check valve do?

The hot water heater check valve has one primary purpose: Keep hot water from flowing back into the hot water heater. The need for this arises from the potential for flooding, corrosion, and contamination. Once a faucet or shower opens for hot water, the hot water heater can send hot water to mix with cold. 

Once this water has passed the check valve, it’s not supposed to come back. If hot water returned to the heater, it could throw off the pressure in the hot water heater by adding too much. The same water should also be prevented from rejoining your drinking water supply.

How does it work?

It’s pretty simple. The valve opens when the pressure is present to send water out. When the pressure to go out is gone, the valve closes. The valve is one-way, meaning that pressure from the other direction (your shower and faucets) won’t cause the valve to open. 

Not all hot water heaters come with one, but you should certainly install one to keep water from coming back.

How will I notice my hot water check valve working?


Ever turn off the shower or faucet while running hot water, then turn it back on soon after? You could get quite the frosty or very hot spray of water right away. 

This blast happens because you normally get a mix of hot and cold water when turning on a faucet. When the faucet turns off without a check valve, the hot water can return to the hot water heater, leaving you without that nice mix of warm and cold. So you get all cold instead!

The check valve stops the water from unmixing. Note that if the water cools down in the process (this will take time in insulated pipes) you might still get cooler water when you turn it back on.

Longer term

Water isn’t supposed to flow backwards, and with heat and pressure, can cause long term wear on pipes and hoses. 

Hot water sitting in the pipes and hoses will wear faster if the water flows back.

The result can also cause additional wear to the hot water itself. While the hot water heater has a pressure relief valve, it’s not something the hot water heater should need to use very often as regulating the amount of water coming from your fresh water tank is preferable to backflowing water.

The hot water heater itself can overflow without proper checks in place. Hot water heater leaks are more challenging because of the temperature of the water, too. 

All of the above indicate the importance of installing a check valve to the healthy functioning of your water system and the prevention of hot and cold water demixture. It’s also a fairly easy piece to install if you don’t have one.

Can a check valve go bad?

It certainly can – to be honest, just like anything else in your RV. The check valve can become stuck open or shut. 

If you aren’t getting any hot water, the check valve might be stuck shut. If you are experiencing that cold water right after hot issue we described before, it’s possible the check valve remains open when the water comes back.

The check valve isn’t difficult to replace. The process mostly involves turning the hot water heater off, letting it cool, and draining it. You can then remove the hot water check valve with a wrench and put a new one in place. 

If your check valve leaks, it either needs to be tightened in place or replaced. A check valve can also drip and leak like other valves. In many cases, this can mean that the rubber seals on the inside are broken or not tight enough.

Where can I find a check valve?

A check valve is most often found at a hardstore store in the plumbing section. They are generally small and should just be a few dollars for one.

You can also order one for delivery online.


The hot water heater check valve can be quite the helpful – and barely noticeable part of your water system. The check valve prevents water from heading back to your hot water heater and causing long term damage to the tank and pipes.

It can also prevent you from receiving an arctic or hot blast of water to the face.

If your RV water heater didn’t come with a check valve, it’s certainly worth looking into installing. You won’t need much more than a wrench, plumbers tape, and a bucket – to drain your tank. 

Now that you know how more about hot water valve, you might appreciate it’s simple mechanics and abilities more.

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