Whether it’s summer or winter, you don’t need to go to a resort to enjoy a relaxing soak in an outdoor hot tub. For a relatively small price, you can build this hot tub in your backyard and take a dip whenever the mood strikes. Fill the tub with a garden hose, light a fire to heat the water, hop in and relax!
The Tub
I chose a Rubbermaid 100-gallon stock tank for a few reasons.
First, it’s deeper than the metal tanks I saw. Second, the plastic itself is a more comfortable temperature in hot or cold weather than metal. Third, its rounded top edges have a larger radius than the edges of metal tanks, so they’re more comfortable to rest your arms on.
Lastly, you’ll find it more comfortable to lean back against the angled ends of the stock tank than the straight sides of a metal tank.
This tank had molded-in brackets for supporting it on a wood frame. I didn’t like the look and they would have made it harder to clad the tank, so I cut them off with a multi-tool.
Several molded styles are available, some with ridges, others without. For the purpose of making a hot tub, any style can suffice. The process of insulating will need to be adjusted if you go with a ridge free tub.
The Water Heater
To heat the water, we used a wood-fired thermosyphon heat exchanger. This 3/4-in. stainless steel coil circulates the water without a pump. It’s based on natural convection, called thermal siphoning.
Cold water enters at the bottom of the heater and expands. Convection moves the heated water upward, pushing it through the coil and out into the tub. At the same time, the heated water is replaced by cooler water below. So there is no need to wire the hot tub — a pile of dry firewood will do.
You can go out and purchase a 60-foot roll of 3/4-in. copper tube and bend a heating coil yourself. But the copper alone costs about the same as this stainless steel coil I found online and had delivered to my doorstep.
ncG1vNJzZmivp6x7p63MoqOyoJGjsbq5wKdlnKedZL2zu8memq1np6S8pXnFoqmenF2dvLV5066ZaA%3D%3D