Simple Solar Water Heater

or… The Saga of a DIY Project by a Local Ascetic

by Dennis Baute

 

Five years ago it looked like the U.S. was seriously interested in reducing our carbon footprint. I expected a cap and trade system or tax reforms that would finally encourage sustainability and conservation.  Renewable energy seemed to be the future (especially in coal-intensive Indiana) but it all seemed expensive.  I’d already lost substantial funds investing in “green” financial stocks and my ability to choose green winners was limited.  Since it was also a time of economic uncertainty I decided to attempt the construction of a DIY solar-heated shower in my back yard as an inexpensive way to reduce my carbon footprint.  My home was total electric and I had already taken many steps to reduce my demand, such as added insulation, new high-efficiency HVAC equipment, new ductwork and lower room temperatures.

My original plan was to build a wooden “hot box” that would house two portable basketball goal bases (the kind that are actually tanks made of blow-molded polyethylene, filled with sand, and often placed temporarily in streets or driveways to support the basketball goals).  I planned to place the hot box on the roof of a fairly new yard barn in my back yard with a southern exposure, place two empty bases/tanks in the box, and fill them with water via a hose to enable a gravity-fed shower system.   The shower location was less than ideal since it had to be near the hot box, but I decided it would be adequate and I envisioned a type of open shower often used near swimming pools to wash the chlorine off our bodies after a swim.  I’d have to wear something while showering, but that was no big deal since most people would look away from my body anyway.

Everything seemed to come together; I had to purchase a new 4X8′ sheet of plywood but I had just about everything else I needed.  I used old 2X4” boards leftover from other projects, obtained used storm windows from a friend’s house that was destroyed in the 2008 flood, and I re-purposed garden hoses found in a neighbor’s trash pile on the curb.  I had paint left over from when the shed was painted and the two basketball goal bases were found in trash piles that hadn’t been picked up from local alleys.  I did have to buy a few wood screws and hose ends, but my total cost would be under $30.

All went well until I tried to make the hose connections with the b-ball bases; it was hard to make connections that wouldn’t leak although I was eventually able to hob some connections together that worked temporarily in spite of the differing materials and hard-to-use sealers.  I used the shower for a couple of days and was proud of my (amateur) work.  Unfortunately, after I filled the tanks with water in their angled positions they fatigued within a few days because of the weight of the water at the very high temperatures in their angled positions.  They failed not only in the hose connection areas but also at the factory-made sonic-welded seams.  It appeared my DIY solar heater would be a failure.  Fortunately, an engineer friend took pity on my plight and recommended a METAL water tank.  Together we located an old 40 gallon discarded gas water heater in the basement of an old house.  I stripped the sheet metal exterior, insulation, controls, etc., flushed out the old mineral deposits, and painted what remained (the actual tank) black.  Although the new metal tank was higher than the planned b-ball tanks & wouldn’t quite fit in my original hotbox, it was remedied with a 2 X 4 addition to make the hot box higher.  Once it was decided to use a metal tank it was an easy decision to pressurize the system.  This allowed me to move the actual shower to another location and protect it with fencing for more privacy.

Once the tank was hoisted to the roof-top hot box (no easy task), the necessary hoses were routed and attached.  From the beginning I knew I would need a cold water source to counter-act the super hot water that would come from the solar box, so I made the necessary connections to allow the addition of a cold water bypass that would “Y” into the shower nozzle with a reversed common hose “Y” fitting.  I filled the tank with water and waited a few hours to see what would happen.  Fortunately I had super hot water, easy temperature control, ample supply, and adjustable force.  Once this was established I purchased a couple of fencing sections along with four  posts (the most expensive parts of the set up).  To avoid standing water I installed slightly elevated patio blocks set in pea gravel (the patio blocks were re-used discards from another house and the pea gravel was obtained from a friend who had purchased it for another project that had never been finished).  I also bought a gallon of paint to paint the fencing so it would match the shed and the solar box.  Despite the use of extensive recycled components I’ve probably spent close to $200 for fencing sections, posts, paint, hose fittings, etc.

Five years on, the system is still performing as intended.  It was improved the second year with the use of a buried Pex supply line between my house’s outside faucet and the solar box.  Every fall I drain the tank and blow the water out of the shallow buried Pex line with the help of a leaf blower (about 30 minute’s work).   Each spring I fill the tank up and check the connections (about an hour’s work).  I’ve had a couple of leaks here and there but they’ve all been minor.  Given the outdoor nature of the system a leak isn’t much of a problem when compared to indoor plumbing.  The system gets used about six months per year beginning around early April (the earliest shower of any year was March 15, 2012).  I normally drain and close the system in mid to late October before freezing weather sets in (the latest shower of any year was November 2, 2012).  At the beginning and end of the season the water is often more than warm enough for continued showers but the outside air temperature admittedly makes things a bit cool (especially on breezy days).  The only change I might want to make in the future would be to move the hot box from the roof of my shed to the ground where it could be easier to service.

During the time the solar hot water heater is in use my electric hot water heater is turned off and my monthly electrical usage is often below 100 kwh.  Last summer my May through October electric bills (a six month period) averaged 124 kwh per month even with the use of occasional air conditioning.   I still turn the electric water heater on when I have house guests (not everyone shares my enthusiasm for the attractions of an outdoor shower).  I figure the system paid for itself in about three years.

A friend notes that a hot shower is “something that should be savored.”  Columbus has plenty of cold water from our numerous area rivers and in the summer I also have plenty of guilt-free very hot water.  My back yard continues to thrive with biodiversity and the extra watering it gets around the shower area seems to be helpful.

If anyone would like to inspect the system, let me know.  Be aware, however, one might easily get hooked on a DIY solar water heater and shower.

Simple Solar Water Heater