My New On Demand Hot Water Heater

So last week I talked about how I was ditching the RV-500 from Precision Temp and moving to a whole new system.  Today I thought I’d share a bit about what I decided to go with instead.

After looking around I had narrowed my options to a propane outdoor on demand hot water heater.  This did a few things for me:

  • It allowed me to regain my under skin storage space
  • Choosing an outdoor version keeps venting very simple, indoor versions require bulky venting
  • I almost tripled my BTU’s from 55k to 150k that meant I could have hot showers on very cold days

There were two major downsides to this option however.  The first was that I was going to have to redo most of my plumbing and gas lines, that meant that it would most likely require a plumber (I don’t like messing with gas lines), which is expensive.  Having to hire a plumber isn’t too bad, but the next downside was the real kicker.  Because the unit was going to be outdoors, if it drops below 32 degrees, most units have a heater.  Heaters are great, because they keep it from freezing, but it’s not great for off grid solar setups.

Winter is a challenging time for solar because the sun is a lower angle, plus its often overcast on many days.  Heating also takes up around 20% more power than cooling, so there are times I need to break out the generator.

What sealed the deal for me was when I talked with one plumber that Rinnai (a tankless manufacturer) had a power failure dump valve kit they could add on.  Basically what this is two solenoid valves that would close the feed line and open a drain valve to drain the water out of the unit.

This meant that if I knew it was going to freeze that night, I could flip a switch to drain the whole unit after I finished cooking for the evening.  If for some reason I forgot or was away, if the power went out, it would automatically drain since the heater couldn’t keep it warm enough.

In total, the unit, the solen0id kit, installation, other parts, and removal of the old water heater came to $2900, which is a lot of money, but after I saw how much work they put into it and how complex the additional solenoid kit install was, I think it was money well spent.  I believe it also meets requirements for a 30% federal tax credit, which is $860 off what I will owe to the IRS.

Initial Impressions:

The unit I got was the Rinnai V53e, which is their value line.  It’s frankly more than I need in terms of capacity, but it’s the smallest in the line.  So far I’m very happy with the unit.  I’ve been using it for 3 weeks now and the biggest change I’ve noticed is that I can take very hot showers, even when it’s very cold out.  Just today it was in the high 20’s and the water was hot enough I had to turn it down a fair bit.  With the RV-500, at temperatures like today, I’d be taking a cold shower even when it was working full steam.

The unit’s pump and vent make more noise that I expected, but it’s not too loud.  In a normal sized house I doubt you’d hear it.  For me it’s mounted on the other side of the wall from my shower so you hear it’s thrumming.

The biggest win is that I get my under sink storage back and the dump valve kit is amazing.  If I’m worried about the heater unit wearing down my batteries.  I just flip a switch and the water is instantly dumped on the ground, problem solved.


Your Turn!

  • How do you plan to heat water in your tiny house?
  1. From the picture, it looks like the depth of the unit – mounted on the outside wall – has increased the overall width of your house. Will this be a problem if you have to move it – like exceeding 8’6″ width?

    • It’s hard to see, but this is actually mounted on the end near the tongue, so no worries there

      • Well OK then! I assumed that the “well” at the lower right of your picture was the wheel well.

  2. Cool article! I like how detailed some of your posts are and this seems like you made a good and reasonable choice.

    I just happened to write an article about water system in (not only) tiny houses. It’s more complex, but water heating is part of it. In case anyone is interested 🙂

  3. Ryan
    I am getting ready to start on plumbing and electrical installation and have to nail down my appliances. I had decided on a Precision Temp floor vent, but after your review I am now befuddled and concerned. I have never really liked the idea of putting a hole in the floor, but not thrilled about the junking up of the exterior either. It is the first negative review I have seen of that mode (at least in the tiny house community)l, but I trust your judgement! I have already purchased the Precision Temp, but am within my free return limit. I would like to hear more about the model you have switched to and how you feel about it after nearly a full winter. Some of my specific questions are as follows:
    1. How is the unit wired? It looks as though it has a 120V plug, is that right? I need to see if it would need to be hardwired otherwise
    2. How much of that $2,900 price tag would you estimate is due to changing out the old install. Quick browsing shows the unit at $515, the solenoid valve package at $300, then add whatever pipe and fittings I need (which I would need for the Precision Temp as well). If those prices are in line with your purchase, then the installation seems pretty pricey. Yikes! I am not comfortable with the propane install and will be hiring most of it out, so I need to budget for that. Besides, it looks like the warranty is voided if not professionally installed.
    3. Could you possibly post a picture of the unit without the guts exposed? I would love to see what it looks like in its natural state.
    4. How cold does it get where you live? I’m concerned about the freezing issue. Do you think it could be installed in my outdoor “shed” which is built over the tongue or would that create ventilation problems?Also wondering out loud how I would deal with draining it. How much water is actually released when drained?
    Thank you for all you do! You have been a great resource for me through my planning process.

  4. …One more thing…
    How do you connect to your water supply. It’s hard to tell by the picture. I am assuming that you have a tank, since you are off grid. Where is your tank? Do your hot and cold lines run under the trailer at all? Again, thinking of the freezing thing.
    That’s it for now, I promise!

  5. The parts in the machine look very good, very well used. Where are the resistors?

  6. I love this. I want the same one for myself. Thanks for sharing.

  7. I have a 500 square foot cabin that has electricity and running water and heat with wood. The water enters the cabin through an underground root cellar that never goes below 40 even when 10 below outside.

    But my sink is upstairs and so far I only have cold water. I have to shut the water off when I leave for a few days in the winter.

    I’m looking for a propane water heater that will also heat the cabin when I leave for a few days. I figure I could set the heater to heat the cabin to 45 degrees or so, then when I stop by I could fire the wood stove for full temperature.

    So is there such a product?

    I also have a tiny propane very old (probably antique) 2 burner kitchen stove with small oven that the prior owner had set up in her cellar for canning vegetables.

    The water heater would be tankless, ideally.

    I have a 50w 240 volt electrical supply to the cabin underground. I ran 6/3 wiring so I suppose I could heat water and the cabin electrically, but I would prefer propane if possible.

    It would be great if I could find a single device to heat my water for showers and to heat the cabin just enough to not freeze pipes.

  8. Hi I’m ready to make a decision re tankless water heater for a thow I’m building for stationary location off grid in Canada. What problems did you gave with precision unit. How di you treat inlet water (I have a well). Appreciate any comments.

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