• Nicholas Nelson

Off the grid hot tub build

Round 3 of my off the grid hot tub build.


So far I’ve tried:

  • Building a rocket mass heater

  • Steel drum lined with copper tubing


And this time, I think I got it.


The set up is:


  • CAMPLUX 1.58GPM Outdoor Propane Tankless Gas Water Heater + 5 gallon propane tank

  • Flojet 03526-144A Triplex Diaphragm Automatic Water System Pump, 2.9 GPM 50 PSI, 12 volt DC

  • Running through a Remes Filter

  • Powered by a 12 volt Marine Battery with voltmeter and 5w solar panel for a trickle charge



Draw from tub comes from bottom (green) garden hose and flows into the filter. From there into the 12 volt pump powered by the marine battery placed inside the door of the tub and into the Tankless water heater. From the heater back into the tun via the steel (silver) hose. The whole system is triggered by a rocker switch mounted on the outside of the tub. Once turned on, the pump kicks over the water heater and the heating process starts up.


Current setup I can go from 70 degrees to 104 in an hour.

Once I hit 104, I can let it sit for a day and it stays +/- 98 and from there, it’s 15 min to get back up to 104-5ish.


Next add is a install a 12V 10A Digital LED Temperature Controller that I’ll have running the entire system to keep within a temp range of 97-104. This controller has a metal tip that will dangle in the water and trigger the pump when the temp drops below the programmed setting and turn off once it hits the max programmed temp.


The entire system draws very little propane, a 5 gallon tank lasts about a month ($20 to refill). If this was on a 220 volt system, the energy bill spike would be somewhere in the range of double, maybe triple the cost of propane tank fill.


All in all one hell of a simple design that should last us years to come.




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Nicholas Nelson 2020