By Robert C. Herman
Any homesteader knows that among the many rewards of
a self-sufficent lifestyle are a sore back and aching muscles. Recently
I realized what I needed to ease the aches and pains after a long day
of chopping wood and moving soil: a hot tub.
Not one of those party-size, fancy marble pools with
jets and bubbles and surround-sound stereo, but a comfortable place to
soak away the knots and contemplate my place in the universe.
Since I haul water, generate my electricity, and basically
live by my wits, the design criteria for my hot tub were: cheap to build,
free to use, and frugal with water.
With about $100, some recycled hardware, and a bit of
ingenuity, I built a thermosyphoning, solar heated tub that uses no electricity,
no fuel, and less than 60 gallons of water, which is subsequently re-used
in the garden.
The principles that make this system work are specific
but simple. The skills and tools required to build the tub enclosure,
and to plumb the system, are rudimentary. The satisfaction of soaking
in my tub as the sun drops over the Rockies is priceless.
Your tub can be made of any suitable container that will
hold water to cover your body. I chose a 100-gallon poly stock tank made
by Rubbermaid Agricultural Products and available for about $70 where
ranch supplies are sold. This tank is oblong, about 2 1/2 x 4 x 2 feet
deep, which is large enough for one person or two very close friends.
It is strong and durable, won't rust, and its rounded edges make it comfortable
to sit in. Rubbermaid makes these tanks in other sizes. If you are extremely
long-legged or plan to share the tub frequently, you might want the 150-gallon
size. For my purposes, though, the additional expense and water requirements
were not justifiable.
The thermosyphoning water heater is elegantly simple
and effective. Basically, it works like this: the solar collector is filled
with water and pointed at the sun. Sun rays penetrate the glass (or fiberglass)
face of the panel, strike the heat-absorbing plate covering the water
pipes, and transfer heat to the plate, the pipes and the water. Since
hot water is less dense than cold water, the heated water rises to the
top manifold, up into the "hot" pipe and to the tub. At the same time,
cooler water from the bottom of the tub drains down via the "cold" pipe
and into the collector's lower manifold to replace the hot water that
is rising. As long as the water collector is being heated and the water
at the bottom of the tub is cooler, hot water will circulate to the tub
and cooler water will return to the collector. This system works well
with no moving parts, provided that you take a few simple steps to help
gravity do it's job (see the drawing).
Back in the mid '70s, after OPEC taught us the fragility
of our dependance on foriegn oil, the federal government offered tax incentives
to encourage the development and use of alternative energy technologies.
As a result, thousands of solar heating systems were built and installed
on houses across the country. Some of these systems worked better than
others and when the tax credit program expired, the solar heating fad
went the way of the leisure suit.
Depending on where you live, it is very likely that there
are abondoned solar collectors nearby, patiently waiting to be rescued
from the scrap heap. Ask around, or advertise in your local newspaper
that you are looking for used solar collectors and associated hardware.
Prices will be negotiable, but I would not expect to pay more than $20-40
for a good 4 x 10-foot collector (you only need one), and for that price
would hope to get a truckload of pipe, valves and fittings thrown in.
Some folks will even give away their collectors and all the associated
plumbing and hardware, just to get it out of their barn or off the roof.
If you really can't find a free or cheap used collector
in your area, you can build your own. My own heating source is a 4 x 10-foot
flat plate solar collector from the late 70s. It's what I had around,
but a smaller collector would do the job, especially if you insulate the
One caveat: make sure the solar collector you rescue
has not been damaged by water freezing inside its works. The flat plate
collector is made up of a series of parallel, small diameter copper pipes
with a larger diameter manifold at each end. If water is allowed to sit
in these pipes at subfreezing temperatures, the pipes will burst. You
can check for damage either by removing the glazing and visually inspecting
the pipes, or but running water through the collector and watching for
Once you have collected the basic components, you need
to site your tub and solar collector. As noted in the drawing, the bottom
of the tank must be at least one foot, preferably two, higher than the
top of the collector. A level spot at the top of a south facing slope
is ideal; the tub sits on the level, with the collector tucked into the
Alternatively, you can site the tub on a platform or
deck, with the collector located below. Make sure, though, that the deck
is strong enough to carry the weight of the full tub (including 500 pounds
of water, plus your own wieght).
There are several considerations to address when siting
your collector. Ideally, it should face south (within 15 degrees of due
south) and have full exposure to the sun between 10am and 2pm. The collector
can be oriented on its horizontal or vertical axis, and should be inclined
at an angle of at least 15 degrees off horizontal (30 degrees is better;
for year round use, the optimal angle of inclination should be equal to
your local lattude plus 10 degrees). Finally, the collector should be
tilted a few degrees so that the lower corner where the return (cold)
pipe attaches is the lowest point in the system and the "hot" pipe comes
out at the highest corner. This helps with the thermosyphoning and with
draining the system down.
Top | Page
Back to Build a Hot Tub
A great way to help save on your water bill with the installation of a new hot tub, is by also installing a flow meter to help regulate water usage.