Wednesday, October 03, 2007

Affordable homemade wood-fired hot tub!

As a new feature for our homestead my partner is currently working on a wood-fired hottub. His design is based on a combination of cedar tubs from out West that are fired up with a chofu heater, ancient soaking tubs from Japan, and small Dutch wood-fired tubs ( The plan is to build an efficient, beautiful, and inexpensive tub, using materials we have on hand.

The basic idea is to start with the size of tub you want - either build one (from cob, cement, metal), retrofit an existing bathtub/clawfoot tub, or, in our case, buy a 150 gallon stock tank from the local farm store. Secondly, insulate the tub as necessary, to help hold in the heat of the water. Thirdly, find a way to heat your water. This can take many forms - either a woodburning stove with a water coil wrapped around, a chofu heater (* see note below), or solar-heated tank. I once lived on an organic farm near Nelson, BC that heated water for their outside shower and bathtub in a large black plastic barrel that was ontop of the shower structure. We took baths or showers at night if we wanted warm water (after the sun had warmed the tank all day long), or cool showers in the morning. This was a very simple design, that is easily manageable for the novice builder - but your property needs adequate access to sun.

In our case, we are hoping to buy an old woodstove, and use a coiled pipe wrapped around it to heat our water. Currently we are heating water in a very rustic way, by the kettle on our firepit which is located beside the tub. Once the main body of water is heated it's actually not that much effort to continue to heat water by the kettle to top up the tub, and have a cozy campfire burning beside us as we lounge in the tub under the stars! For our guests, the woodfired model would be more suitable.

The photo shows our tub, with two sitting benches inside, and the insulation layer. We have a large volume of old tongue&groove boards in our barn, and this is going to be the outer covering, followed by a wider platform on which to sit around the edge of the tub. More photos to come as this project unfolds...

* Note on the chofu: The chofu is a precision built wood-burning water heater designed specifically for hot tubs. It circulates water using the principal of thermosiphon (the pumping action created by rising hot water), eliminating the need for a circulating pump or electricity. This unique feature opens up a whole new range of possibilities for alternative hot tubs. Now you can have a basic soaking tub without pumps, chemicals, or high maintenance. With the chofu heater you can retrofit an existing tub or put together a low-cost soaking tub, using a wooden tub or stock tank (from

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