How To Save Water And Solve The Cold (Or Hot) Water Blast In Your RV Shower

Have you ever wondered why your shower head drips when you put it in pause mode? It should maintain the temperature of your water. If you shut it off completely, you also close your hot and cold valves, and when you reopen them, you waste water to regain the right temperature.

By letting it drip for a bit, you prevent this from happening—in theory.

While I was doing research, I found a lot of people on forums or in YouTube comments who claimed that this doesn’t work. You still get a cold or hot water blast when you turn the shower back on.

So why do some people complain about this and others don’t? Well, I searched the internet for an answer and found one: many RV’s don’t have their water pressure right. The pressure in the cold water lines is higher than in the hot water lines. So when you turn off your shower, the cold water backs up into the hot water line. And when you turn it back on, that’s the first thing that comes out of your showerhead.

So how are you going to solve this problem so that you never have to worry about a cold or hot water blast again? There are two ways to fix this, and which one you’ll need to approach depends on your situation.

How To Fix It

Option 1: Installing A Shut-Off Valve On Your Showerhead

This is really simple to do and the only thing you need is a shut-off valve. It’s nothing more than an on-off switch for your shower head, so it’s a great way to save some water. It will also prevent the cold water blast IF nobody else is using water while you’re showering.

So why does this work? If it’s not leaking, the cold water can’t back up into the hot water line because it’s turned off and simply not able to move into the line. This changes if someone else’s using water.

If that doesn’t bother you, you just need to buy a shut-off valve that you can screw either:

  • Between your shower head and shower hose
  • Or between your shower hose and the faucet

an rv shower

You just have to make sure that your shut-off valve is the right size, otherwise, you won’t be able to screw it on. If you live in the US, you probably need a shut-off valve with the standard 1/2″ connection, such as this one. If you’re not sure, you may want to measure the diameter of your shower head/shower hose where the shut-off valve is to be connected. This WikiHow article shows you how to do that.

And finally, you’ll also need some Teflon tape to ensure a watertight seal.

If you have everything you need, you can proceed and follow along with this video. If you click the play button, it takes you to the correct timestamp.

Option 2: Installing A Shut-Off Valve And A Check Valve

Now, if someone else is using water while you’re showering, a shut-off valve alone won’t solve the problem. You also need a check valve so that your water flows in only one direction.

You’re going to need a few things:

  • Teflon tape

To ensure a watertight seal between the connections.

Teflon tape

  • A shut-off valve

To make your showerhead stop dripping.

  • four shut-off valvesA check valve (also known as a one-way valve)

To prevent the backflow that’s causing the cold water blast.

a one-way valve

But before you dive into your local store, you may want to find out what kind of check valve you need.

What Kind Of Check Valve Do You Need?

At the time of writing, there are two videos on Youtube that address the problem of the sudden hot/cold water blast. However, both are different because they both have a different hot water line. So that means one video is going to be useless to you.

Maybe your hot water pipe is connected to your shower’s pipe in the same way as in this video:

If that’s the case with your RV, you need a check valve with MPT threads on one side and FPT threads on the other side (if it’s not, you can safely scroll to the next subtitle).

MPT stands for Male Pipe Thread. The threads are on the outside and you can see them. You can screw them together with an FPT (Female Pipe Thread), which has the threads on the inside.

A check valve with male and female threads
A check valve with male and female threads.

Which size it should have depends on your RV’s tubes but probably something like 1/2″ in diameter (standard in the US). But it may be different with your RV, so if you’re not sure, make sure you measure your pipe’s diameter before buying one.

If you’re sure you got the right size, you can proceed and follow along with the video above.

Here are the steps you’ll need to follow:

  1. Find the hot water line your shower’s connected to.
  2. Make sure there’s no water coming through.
  3. Disconnect your shower’s tube from the hot water line.
  4. Screw the check valve to your shower’s tube.
  5. Attach your hot water line to the other side of the check valve.
  6. Install the shut-off valve on your showerhead.
  7. Done!

What If Your Hot Water Line Is Made Of PEX?

If your RV’s hot water line is a PEX pipe like as shown in this video:

Then you’ll need to do something different because you can’t just connect a ‘normal’ check valve to a PEX pipe. So how does the guy in the above video fix this? Well, he suggests using two push-to-connect fittings to connect the check valve with your PEX hot water line.

However, this seemed like a detour for me. I searched the internet for a check valve that simply has a push-to-connect connection on both sides… And with success! A check valve like this one does the job. It’s a SharkBite check valve that is compatible with PEX pipes, which is exactly what you need.

the guy in the video who admits that this is a better method
the guy in the video who admits that this is a better method

So how do you fix this with the SharkBite check valve? Exactly like the guy in the above picture tells you. You make two cuts in your PEX pipe so that you can slip the check valve between the cut ends. It’s important that you don’t cut too much though, because you could really screw yourself at this step. If you cut too much, you won’t be able to completely seal the PEX pipe in the check valve, and you really want to fully seal it or you may end up with a leak.

The video below shows you how to use a tool to cut your PEX pipe. On top of that, it also provides some valuable information that you may want to know about. If you don’t have a PEX pipe cutter yet, make sure you get one that’s capable of cutting the thickness of your PEX hot water line.

In the following two pictures, you can see a visual outline of the situation. I also explain where and how much you need to cut. Check it out.

Find out how deep you have to push your PEX piping on this page. Alternatively, you can buy something like this, which is called a ‘Depth Gauge Tool’. Here‘s a video that shows you how to use it.

If that’s done, the only thing that’s left to do is installing the shut-off valve on your showerhead (if you didn’t do that already). Click here to jump to the tutorial.

If you followed the steps, you won’t have to worry anymore about leaking showers or cold blasts of water.

Let me know in the comments how it went and what you think of this article. If you want to contact me, you can do that on this page.

Thanks for reading!

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2 thoughts on “How To Save Water And Solve The Cold (Or Hot) Water Blast In Your RV Shower”

  1. Excellent post! You cover almost everything you need to know about solving the “cold blast” problem. I’m hoping that installing a good shut off valve at my shower head (or where it comes out of the faucet) will fix this problem. But if it doesn’t (as you noted, when other people might use water while I’m showering), I’ll have to install a check valve (one way valve) in the HW line. So, here’s my question: Does it matter where I install it? The closest place I can get to nearest the shower valves is in a cut out area under the shower, but it’s VERY tight, and the cut I need to make may be a “blind cut”. So I would like to install it in the line right outside the HW tank. Since this is a closed system, tis shouldn’t make a difference, right? Or am I missing something? Thanks for your input!

    1. How effective the one-way valve is at solving this issue depends on how close it’s placed to the shower’s mixing valve. If it’s far away, then you’re still going to get the cold blast because the hot water lines will still be affected by the cold water.

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