How to Build a Hot Tub

Enlarge Image Image Gallery You can customize your DIY hot tub setup to your wishes. This backyard design includes a wood-fired heater, a handy storage nook and a small shed for stacking wood. PHOTO: GREG KOSSOW

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I have lived in the Pacific Northwest with its cool, damp winters for more than 20 years, and I always wanted to build a hot tub. I wasn’t interested in one of the popular jetted tubs because their cost is prohibitive, the pump noise and vibration are bothersome, and the chemicals used to keep the water free of bacteria are a turnoff.

The idea of using a stock-watering tank for a DIY hot tub project has been around for a long time, but all of the ones I’d seen were pretty unattractive. I wanted a setup that was nice-looking, easy to use and economical. My hot tub dreams came together when I discovered a wood-fired spa stove made in Japan by a company called Chofu and imported by Island Hot Tub Co. Depending on how the soaking area is customized, the setup I’ve designed can cost less than $1,000.

Soaking in a Wood-Fired Hot Tub

Unlike a commercially available tub that only requires you to plug it in and set a timer, you’ll be more involved in the operation of your wood-fired soaking tub. The water is not continually kept hot, so each soak needs to be planned a few hours in advance. I find the involvement is part of the attraction. It creates anticipation that starts with building the fire and culminates with climbing into the steamy, relaxing tub.

The Japanese have long recognized the benefits of soaking in hot water to relieve aches and pains and deal with the daily stresses of life. They typically bathe before soaking to avoid dirtying the water and to maximize the number of times the water can be used before it requires changing. Before each soak, I wash up using hot water dipped directly out of my tub. This keeps the water clean and also acclimates me to the water temperature. Traditionally, the Japanese tend to like their water exceptionally hot, but the Consumer Product Safety Commission recommends the water temperature in a hot tub never exceed 104 degrees Fahrenheit. I keep a hose handy to add cold water if necessary.

Heating and Maintaining the Water

The tub I chose holds 100 gallons if filled to the brim. That much water costs about a buck in our town. Fill the tub 3 to 4 inches from the brim, otherwise the water displaced by your body will be lost when you get in. This setup uses considerably less water than commercially available tubs, thus making it more practical to drain the water frequently, keeping it free of bacteria without using toxic chemicals.

With daily use for two people, we replace the water every four days. When the water needs to be changed, you can simply drain it into a garden area. If you want to keep the water longer or are worried about bacteria growth, add about a quarter cup of 35 percent hydrogen peroxide per 100 gallons (wear gloves and safety goggles during handling). Hydrogen peroxide at this strength is sold as a water clarifier in spa stores. It separates into hydrogen and oxygen in the water, and the oxygen is the active ingredient that kills bacteria.

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