Please don’t sue me for this…

We love LPG. Both our stove and fridge are incredibly efficient. The furnace, well, they had to design it with carbon monoxide emission safety as priority one, so it’s nowhere near as efficient. But the shower situation, with a 6-gallon tank, was neither efficient nor comfortable. It was the one appliance that made me miss living like People. I like a nice, HOT, LONG shower, and for Meg, you can double the length (although she doesn’t go for the sauna-condition I like, so it works out – we probably use the same amount of gas). Six gallons doesn’t give you enough time to rinse soap out of your hair. It’s like having a cellphone with a 20-minute battery life that constantly sucks power. It had to go.

But where?

I first started looking at tankless electric heaters. “Tankless” refers to water flowing directly through a heater coil. It comes in cold and goes out hot, without sitting in a storage tank. So you can take as long a shower as you like. BUT…it consumes a phenomenal amount of electricity. I naively thought that, hey, my 1800-watt generator runs an AC system just fine, so those same 1800 watts ought to be able to heat up a bit of water, right?

Wrong. Try 13 KILOwatts. About 7x what my otherwise adequate generator puts out. I frankly am puzzled from an engineering perspective why someone can’t make more heat from less juice, but no one I found did. The only electric water heaters operating at 1400 watts are tiny, point-of-use units designed for handwashing. At 2.5 gallons, they are useless for a shower.

This was disappointing. Because you simply CANNOT run an LPG heater INSIDE your RV. Because you will KILL yourself with carbon monoxide. Anyone you ask online will tell you so. But… what if you are stubborn, not risk-averse, willing to take a gamble, and used to work in the American Institute of Architects’ Building Codes and Standards group, and know the difference between Code and reality? What if you knew enough about HVAC to do the requisite math and determine whether or not the 12″ open skylight, positioned at the top of your phone booth-sized shower stall would, if the exhaust fan blades were reversed to draw air IN (rather than blow bad smells out), provide enough fresh air to keep properly-vented CO at a safe level? Well, then you might try this:


And by God, it’s AWESOME. Note: IF YOU TRY THIS, AND YOUR SETUP IS ANY DIFFERENT THAN MINE, YOU MIGHT KILL YOURSELF. THE MANUFACTURER SAYS SO. And so does every other source I found on the internet. But… Here’s how and why this works safely for me. I take no responsibility for you.

  1. The heater is vented directly up and out through the roof with insulated pellet stove pipe. CO is very slightly lighter than air, so it WANTS to go up the pipe. If you try and run the pipe out through the wall, things might change. I don’t know.
  2. There is an OPENABLE skylight on the ceiling that covers roughly 40% of the ceiling surface area. When the skylight is open, there is ample fresh air.
  3. Because I reversed the blade on the exhaust fan, there is positive pressure of fresh air coming in. This blast of air is looking for a way out. The chimney on the heater is the easiest route. The combination of heat and light weight of the exhaust creates what HVAC techs call “gravity feed” – up & out is where the gas WANTS to go.

I have been using this setup for three months now and have checked it with a CO meter while running. It stays green, even after 20 minutes of running. The fact is that this works safely DESPITE breaking every rule: it’s not only inside (manufacturer warning number 1: do not use inside), but it’s in a tiny space, with only 70 or so cubic feet of air. It’s a murder machine, a carbon monoxide suicide capsule. But the huge open skylight and positive pressure draw enough fresh air to make it operate safely. Just don’t try this at home. It will supposedly kill you.

I got cocky and decided (while holding my breath) to see how long it would take the CO meter to go off if I left the skylight shut. It took about ten seconds – but just as the CO meter went off, the heater shut down. I repeated this experiment multiple times. I’m not sure if the manufacturer built in a safety shut-off (they don’t mention one, but then they wouldn’t – that would be a liability), or if it simply runs out of oxygen to keep the flame alight. That seems more likely. I’m not saying it’s idiot-proof (far from it), but it doesn’t seem to be a very reliable suicide machine either.

This post has already gotten too long – if there is interest, I’ll post info on the heater itself (which is AWESOME) and what it took to install it.

One nice thing about living in an RV is freedom – not just to go where you want, but to come up with your own Building Codes and Standards.


One Comment Add yours

  1. mareyheater says:

    Hi! Thank you so much for sharing your experience with a Marey gas tankless hot water heater! We greatly enjoyed reading how you were successfully able to creatively install this unit and hope that you enjoy endless hot water for many years to come! Please feel free to reach out to the Marey Customer Service department for any questions or concerns you may have regarding your current Marey heater or any of the new products we are introducing.

    Best Wishes!
    Madilynn Pietsch
    Marey International LLC


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