Build a Thermosiphon Solar-Heated Shower System

Reader Contribution by Kyle Chandler-Isacksen and Be The Change Project
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Solar panel and water tank.
Photos by Kyle Chandler-Isacksen and Be the Change Project

A few years back, a friend donated a Sunvelope solar hot water panel. We were just about to expand our greenhouse, so the timing was perfect to incorporate a solar shower.

The system is pretty basic, with a panel mounted south and tilted to catch more rays just outside of our greenhouse and an old water heater tank positioned higher than the panel. Ours is a thermosiphon: Water circulates simply because of temperature differences with no need for electricity. It is also not plumbed to our house water source but instead is an isolated system, which we have to fill after about seven showers (more on that below).

How to Build a DIY Solar Hot Water Heater

Used water heaters can be found on Craigslist or Facebook Marketplace, no problem. It doesn’t matter if they work or not — just make sure they have no leaks. The heater has a cold and hot water port and a drain. For our purposes, it didn’t matter which port we used, because the water will circulate throughout the tank and to and from the panel.

I ran 1/2-inch PEX tubing from the high end of the panel (the hot-water outlet) to the tank and then from the tank back to the panel on its low end (intake). Before it cycles back to the panel, however, I put a “T” in the line and ran that into our greenhouse shower with 3/4-inch PEX. I think I just happened to have 3/4 lying around or I would’ve just used 1/2-inch throughout.

I both painted the PEX and covered some of it with a plastic pipe cover to prevent breakdown in the sun. I also tilted the panel forward a bit so that the outlet is lower than the inlet, which gives us a little more water to use before we have to fill it again.

At the bottom of the tank, I put another “T” before the intake and attached a short line to a valve. When we need to fill the tank back up, I just hook our hose to it and open the valve and fill it up from our outdoor hydrant. This valve also allows for easy draining of the system in the winter.  If you’ve never worked with PEX before, it has revolutionized DIY plumbing. It is so easy these days to connect and crimp and run lines wherever you need them with very little skill or knowledge.

Maintain and Use a Simple Solar Hot Water Heater

It’s wonderful to shower in our Nevada greenhouse, as the air is warm and humid and the water we use in the shower helps grow our plants. This year, we took our first outdoor shower in March during a warm week and generally use it into November.

In high summer, I cover half the panel with plywood to prevent it from getting too hot, because I don’t temper the water (mix the hot with another source of cold water). I could figure that out, but this it just so simple and easy that I’ve never felt that ambitious. During those hottest days, we generally take showers at the end of the day or in early evening when the solar panel is not heating so much, so the overall water temp is lower. It’s another way our appropriate technologies help us stay in tune with and appreciative of seasonal changes.

The Sunvelope (which happen to be made in neighboring Sparks, Nevada) is a great panel that will not burst and freeze in the winter. I do drain the system when the cold weather sets in, though, to be sure the PEX, the tank, and any connections don’t bust.

Kyle Chandler-Isacksen is a tinkerer, natural builder, and community organizer in Reno, Nevada. He and his family run the Be the Change Project, a fossil fuel-, car-, and electricity-free urban homestead and learning space dedicated to service and simplicity and inspired by the principles of Gandhian Integral Nonviolence. They were honored as one of MOTHER’s Homesteaders of the Year in 2013. Read all of his MOTHER EARTH NEWS postshere.

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