How to Fix the Cold Water Blast in Your RV Shower

The usual way to shower in an RV involves shutting off the water a few times, so most RV shower heads these days include a shut-off.  This would be a great idea if it weren’t for two things:

  1. The shut-offs usually leak horribly.
  2. Typically, you get frozen or scalded when turning the water back on.

In our RV, we were getting frozen out by the shower head shut-off, so I finally decided to do something about it.  This video is the result:


The problem here is something called “crossflow”.  Crossflow can occur when you open the hot and cold water taps, and connect them together.  This is what happens in a shower head, where you allow the water to mix, and then shut it off someplace after that.  This will allow the water to flow from cold to hot, or hot to cold.

Which way the water will flow depends on whether your hot or cold water was at the higher pressure.  In our RV, the cold water was at a (significantly) higher pressure than the hot water.  This was allowing the cold water to push its way back down the hot water piping – leaving us with nothing but cold water when we turned the shower head back on.

Now if the hot water was at a greater pressure than the cold, you could have the reverse situation happen.  This would leave you with nothing but hot water in the shower and plumbing lines, and could potentially scald you.  That would be bad!  I’ve not found a definitive source on this (I’m sure someone will correct me in the comments if there is one), but the theory is that shower head manufacturers are guarding us against such a scalding by building shower heads that leak – on purpose – when the shut off is engaged.

That’s a cute idea and all.  But it doesn’t actually work, and just wastes water.

I started off just trying to fix the cold water, but later realized I needed to fix the leaking as well to solve the whole problem.  So I wound up installing a check valve (on the hot water, to keep the cold from working its way down that line), and also a shower shut off valve that actually worked.  (Most shower shut-offs that you’ll find also exhibit the leaking).

If you want to play along in your own RV, here are the key parts I used:

And if you have a Winnebago Travato 59G like we do, you’ll also need to order this gasket:


Travato Door Seal Part


Beyond that, the video is pretty self-explanatory.  One word of caution though:  Since we are talking here about defeating a reputed safety feature, be sure you know what you’re doing!  If, for example, your hot water was at a greater pressure than the cold, you would have to move the check valve to the cold water piping, or you would scald yourself.  If the above doesn’t make sense to you, I’d recommend you don’t try this yourself, and instead, consult a plumbing or RV service professional.  I don’t want to be responsible for anyone getting scalded!

I’m happy to report that after these additions, our shower stays at a constant temperature when the flow is shut off.  The leaking has stopped as well!  Hopefully, this helps some of you out, too.


James is a former rocket scientist, a USA Cycling certified coach, and lifelong fitness buff. When he's not driving the RV, or modifying the RV (or - that one time - doing both at once), you can find him racing bicycles, or building furniture, or making music. In his spare time, he's also an IT consultant.

    53 thoughts on “How to Fix the Cold Water Blast in Your RV Shower

    1. jonathan palmieri

      Thanks for the great video. Unfortunately the check valve would not fit behind my shower body as the wall is not deep enough. The good news is that the new shut off valve alone greatly reduces the cold water blast!

      1. James - Post author

        Bummer about the check valve. But glad to hear that the shut off worked for you.
        Thanks for reading!

    2. Dany Grondin

      Is putting 2 check-valves (one for the Hot Water and One for the cold water ) would prevent any possibility of scalding?

      Thanks for the video , very interesting

      1. James - Post author

        As long as the check valves were upstream of any connection between hot and cold piping. And as long as you took care of any dripping from the showerhead… yes, I believe it would.
        (But I am not a licensed plumber, so I’d advise you to et a second opinion.)

    3. Bill B

      Since I use the dry method to winteruse (compressed air to clear the lines), do you have any ideas on how I could insure the outlet side of the check valves would be cleared of water? I currently use low point drains. I open the drains and all fauvets until nothing else comes out. Then I connect my air, let it blow, more water out, close all valves, pressurize to about 40psi, open low points. I repeat until I don’t see any more water from anywhere. Bill

    4. James

      Great Job ! I had wondered about our leaky shower head (2016 K) but hadn’t showered yet to learn that problem. Thanks for the fix !

    5. Craig

      Now that you are done and your problem is solved, in hindsight, do you think the check valve is really necessary? I’m thinking the shut off valve would solve the problem without the check valve.
      Not criticizing, but thinking out loud. Thanks for the links and idea, I’m ordering the shut off valve for mine.

      1. James - Post author

        I do think the check valve was necessary. With the pressure difference as great as it was, I would certainly have had some crossflow until the pressures equalized. I think it would have made the problem worse.
        As a follow up, showered after my race this weekend and it worked like a champ!

    6. Larry

      Here’s what I’d always heard: A standard showerhead shut-off valve drips to prevent the shower hose from bursting, stretching or leaking from the built-up pressure. The hose is supposedly less strong than standard piping and the drip relieves some of the pressure. Adding a shut-off at the base of the hose avoids that problem.

      1. James - Post author

        That’s an interesting theory. I could buy into that. But that still doesn’t explain why the shut off valves I purchased from the home center leaked on purpose. I guess you could say they were intended for the shower head end of things, but still… should be sold as something other than a “shut OFF valve”.

    7. Rocky

      Out of curiosity, is there a hot / cold pressure difference when using the city water hooked up, or only when using the pump.

      1. Stefany

        Hey Rocky! We suspect so initially, but it would equalize the longer you’re hooked up to city water. But this is just a guess, we’ve never hooked to city water.

      2. Dan

        The Truma has its own pressure regulator as part of its plumbing. I suspect the issue James fixed in this video came about because of that pressure regulator in the Truma line (no, don’t take it out though!). The cold water is coming in at whatever pressure is in the line, from the pump or from city water. The hot is further reduced in pressure. And there’s a lot of extra pluming, and the Truma itself, so adding it all up, the pressure will be lower on the hot side. I would expect this to happen on city water just as it does on the pump.

        1. James - Post author

          I suspect you’re right – the pressure difference would be there regardless of using the pump or city water.

    8. DENIS S

      Great tip, we have the same issue.

      Looking at the shut-off valve on Amazon it I’d offered in 3 sizes… A size name field… Which one did you get?


      1. James - Post author

        I ordered the “ABS Handle” model.
        A plumber could explain better the difference between NPT and IPS threads.
        My understanding is that the IPS versions seal with a washer, and NPT seals on the threads.
        In this case, since I had a washer in place on the shower hose, I went with the IPS version. Chose the ABS handle because it seemed smaller, and it was a small fixture.

    9. Mark Roberts

      Riddle me this…

      If there is one water pump in the system, why oh why is there a difference betwixt the pressure of the hot and cold outlets?

      I can understand that the flow rates could be different as the hot water has to go through more plumbing, but the pressure should be identical!

      Congrats on the insulated interior plumbing! Makes me ever so slightly envious 🙂

      1. James - Post author

        My theory on the different pressures:
        At the pressures we’re talking about, air is compressible. Water is not.
        There would be a slight air space at the top of the hot water tank. That air compresses, and thus, the lower pressure in the hot water system.
        I didn’t want to spend the time to test it, but if that is true, and I left them connected through the shower long enough, they would eventually equalize as the air compressed to the same pressure as the rest of the system.

        Insulating the piping was a bear of a job, but I’m glad I did it!

        1. Mark Roberts

          Even with an air space, the pressures would still be equal, albeit lower. I think you are missing something fundamental, and should start all over again! 🙂 (Easy for me to say!)

        2. James - Post author

          Well, the pressures might be equal if the two sides of the system were equal (or close). But there are drain valves, check valves, regulators, Temperature/Pressure relief valves, and winterization plumbing on the hot water side that don’t exist on the cold water side.
          I’m also mildly curious as to why the cold water side pulsed so much with the system sealed off. There were no leaks… why is that pressure dissipating so quickly?
          Regardless of what causes the difference, its unpleasant consequences are fixed now!

    10. Richard Kilbride

      Hi from over the pond. I have a Ducato based van, a Trigano Tribute, an Italian PVC as we call them here, Panal Van Conversion. It does not have your problem with the shower as it has a lever controlled tap ( faucet).
      However I noticed during your vid that your pump was cycling badly. This problem can be fixed easily by fitting an accumulator tank, which contains an air bladder which you pressurised with a bike pump and this equals out the flow causing your pump to work both quieter and more smoothly. Stops those annoying clicks in the night as the pump pressures up the system. Fiamma make a small one and its easily fitted as close to the pump as possible.
      Can I suggest a couple of free sites that might be of interest. My own, a free wilding forum for the UK and Europe and the main site for our tribute buddies, that has a wealth of knowledge on the Ducato base it’s been built on for 10 years.
      I share many of your very helpful vids on both sites.

      1. James - Post author

        I’ve thought about an accumulator tank. But there’s very little space near the pump to mount one.
        Previously, in another rig, I had swapped out the pump for a VSD pump. That had the same effect and worked well.
        In the Travato, this hasn’t been enough of an issue to bother us. We try to only turn on the pump when we are directly using it.
        I’ll be checking out those sites. Thanks for the links.

    11. BobB


      It seems there are some other things going on under your sink – I see at least one ball valve under there – so it seems having “easy” access under there would be beneficial. Do you need to get access there often and do you need to go through the “replace gasket and silicone” routine every time?

      So that little gasketed cabinet – do you really use it? Or would it be better to just replace it with a “marine” access hatch and store whatever elsewhere?

      1. James - Post author

        That was only the second time I’ve been under there. The first was to install the insulation, extra trap, and ball valve as part of our Travato Winterproofing project. The ball valve shuts off the water to the exterior shower in back. I don’t see us turning that back on, ever, until we sell the Travato. (The exterior hose isn’t something we want or use.)

        Stef does store things in the cabinet normally. I have thought about changing it somewhat to allow easier access to what’s behind. But it’s pretty far down my list.

    12. David Brimhall

      We, or at least I, have not experienced the cold or hot water blast when taking a shower. BUT, every shower head we’ve used leaks when turned put on hold, UNTIL we finally found one at actually turns off. We found it from some online RV store. It’s named Relaqua. This is our third one and its a keeper.

    13. Mike Ortino

      Great James
      I like your determination to get to the bottom of a problem. Your fix is well thought out and I enjoy your showmanship.
      Thanks for keeping us informed.

      1. James - Post author

        Thanks Mike!
        There was a lot of, um… showmanship I left on the cutting room floor. Typical swearing-and-scraped-knuckles-and-banging-your-head-while-trying-to-work-under-the-sink kind of stuff…
        Eventually got it solved, and we’re happy with the end result.

    14. Jim

      Great solution to a VERY annoying problem. If I can pull this off, I will be a hero.
      And, I’m telling her it was my idea. Shhhh.
      Thanks James!

    15. Alain

      My solution might be too simplistic, and certainly less entertaining. But since it’s a hand held shower head, why don’t you just aim it at the shower wall, floor or less sensitive body part for a couple of seconds when you switch on to flush the cold water. Probably won’t take too long or waste much water.

      On another subject, in your video, I noticed you have an Oxygenics Body Spa shower head in your house. This shower head is often recommended as an RV upgrade shower head because of the reduced water consumption and good pressure. I’m surprised you don’t have one in your RV.

      1. James - Post author

        We were solving the problem your way. The trouble was, we kept forgetting!
        You’re right about the Oxygenics in the house. I had installed one in our last RV, and we liked it there. I would prefer to install one in Lance.
        But Stef is more picky about shower heads and she likes this one. Since she has… you know… HAIR, she gets the deciding vote.
        I’m working on her though. Perhaps we’ll have one before too long.

    16. Mike Fisher

      From a Plumbers Son…spot on James and the combination of both valves did you right. To bad the industry can’t do that and I am sure it’s do to some sort of a liability question and or problem.
      A problem of leaking hot or cold water fixed in a quick way! Thanks James for the clip for everyone to see to be able to handle this DIY project!

      1. James - Post author

        Thanks, Mike
        (I didn’t actually consult a plumber before making the mod, so I appreciate the endorsement!)

    17. Steve B

      Great piece of Investigative Reporting in a DIY video!! This should be “Required Viewing” for all RV Owners!

      1. James - Post author

        Thanks, Steve!
        It took me three weeks to finally finish that video. Once I get started with something, I tend not to let it go…

    18. JHolly

      Well a friendly massage therapist, I recommend hot and cold water showers to boost your immune system and keep you fit for cycling or yoga lol. However, I would jump not prefer it to have a cold blast. Thank you for the experiment and guidance.

      1. James - Post author

        I suppose I didn’t. It’s a quarter turn ceramic disc valve with a thumb lever. If you check out the link to the valve in the write-up, there will be detailed pictures of the valve, and it should be evident how to operate it.
        Suffice it to say, I don’t think we’d have any problems, even with soap in our eyes!

    19. Dan

      If you are unsure if your hot or cold is higher pressure, or to be extra safe, install a check valve on both, hot and cold, then install the shutoff valve.

      1. James - Post author

        I had actually purchased two shut off valves to do just that, which I agree would work.

        I elected not to install the other one because every connection is another opportunity for a leak. And since I had verified the pressures, I knew I was installing the one where it needed to be.

      2. Tom

        Great idea. I don’t have a meter/gauge to measure the water pressure. Buying two valves is probably cheaper than buying one valve and a gauge.

        1. James - Post author

          Yes, even decent quality metal bodied valves like I used are fairly inexpensive, and would give you extra piece of mind.
          I already had the gauge. It’s not terribly expensive. I have this one, but there are cheaper ones.

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