"Although it may seem impossible, I'm here to tell you, you can enjoy a hot tub on the side or top of any mountain you choose."
When we set out to live and travel the country in February one thing we didn't want to give up was our hot tub. So we started researching how we could run the built in heater off the 1200 watt solar system we had installed in our Airstream Nest, and with it drawing a constant 1500 watts, we were almost sure it wouldn't work. My wife, had been doing some research on the topic and came across a on demand hot water heater that people have used to fill their hottubs. This would allow you to fill the hot tub with water from 80 to 130 degrees depending on the temperature you select. However, then you would still have to use the 1500 watt built in hot tub heater to maintain the temp you desire. With a little more research and brainstorming sessions we discovered a solution. Our solution was to create a hot water loop that would filter the hot water out of the hot tub and thru the on demand water heater, then back in to the hot tub. This way we would only use about 25 watts of energy as the tub filters thru the water loop. The heating is done by the propane on demand water heater, and we have it programmed to run 5 minutes out of every hour. With a few trial and error moments, we have now perfected the system. Here is what it looks like today, and here is a list of materials we used in our setup.
First, You need a Inflatable Hottub. We went with the Goplus 4-6 Person Inflatable Hot Tub Portable Outdoor Spa Bubble Jet Massage Spa w/Accessories Set (6-Person, Gray) You can get it on Amazon and we love this one and give it a 5-star rating!
Next, and most important, is the on demand hot water heater. We tried using a use a low cost, on demand heater only to realize that it had problems with the pipe connections and the internal part quality did not met our needs for this project. We actually ended up designing a plan that allowed us to use the factory installed system in our Airstream Nest. It is a Suburban’s NAUTILUS On Demand RV Water Heater and it works perfectly for our design. You can look around on Amazon as there are many options there but I would stress to you to purchase quality over price. If I didn't already have the on demand system installed by Airstream in my RV, I would purchase the Eccotemp i12-LP water heater, 4 GPM, Black.
Another key component is the water pump. We are using the Shurflo 4048153E75 Electric Water Pump. Ours is part of our (moveable) set up that we have next to the hot tub. This could also be permanently mounted in your rig if you desire.
The filter that comes with the hot tub gets dirty fast!! So we added additional filters to the system to improve the quality of the water. The filter before the pump is a 50 micron spin down filter and catches hair and skin cells. The filters in the hot tub can be purchased here and they will only last about a week if you are in the tub daily. Intex Filter Type S1 Easy Set Pool Cartridges - 6 Pack. The string and paper filters that we have added last about 1 month with regular use and can be picked up at Walmart, or any hardware store or Amazon.... I love Amazon!
A programmable timer allows you to set how many minutes per hour you want to run your hot water loop. We have decided 5 minutes per hour maintains a good temperature once the hot tub is at your ideal temperature. The concept here is to pull water from the hot tub, clean/filter it, heat it to 130 degrees thru the instant hot water heater and then add it back to the hot tub. This has proven to keep our tub between 100-105 degrees. We have tried a few different timers and this one is working well. Yardeen Water Timer Electronic Hose Sprinkler Garden Irrigation Controller Two Dial Color Blue
There will be additional parts you will need to make this work for your application. We use garden hose for all of our connections because we don't set the tub up in the same place every time. This allows us some flexibility to move the hot tub around. We also use some shut off valves to work as a on/off switches that can be reached from inside the hot tub since the pump is a on demand style rv pump. I shot a very simple video illustrating some of the things discussed in this article to give you a better idea of exactly how our system is set up. Take a look... and if you have any questions please feel free to reach out to us via Facebook or Instagram. Also, Please take a look at the Hot Tub Set up Page on this site.