How to Make a Wood-fired Outdoor Shower

This past summer we made an outdoor shower. We have an indoor one that we use most of the time but there is something cool about showering outdoors rather than in a tiny room. If you don’t mind cold water when bathing you can always just hose yourself off but we wanted hot showers. We put the outdoor shower at the other side of our property so that guests who come and camp with us can use it. It was really built for them.

To heat the water, we built a wood-fired water heater. We learned how to do this in Mexico at a gorgeous property in the bottom of the Copper Canyon, on the Rio Urique. Friends of ours own this seven-acre paradise, that is also a rustic B&B, and I had the pleasure of being able to house-sit the place a few times. I promise to write an article sometime all about my experiences at Entre Amigos, this beautiful off-grid place on the river in Mexico. But I digress.

To make a wood-fired water heater on the cheap you need to find a gas water heater that has been decommissioned due to something other than the tank or the fittings rusting out. Sometimes the valves go out, or the burner rusts, or sometimes people just want a bigger water heater and you can get their old, perfectly good one for cheap or free.

A gas water heater’s tank is like a really tall doughnut, with a hole up the middle of it for the exhaust gases from the burner to escape. What we are doing to make it wood-fired is replacing the gas burner with a small fireplace. The water heater itself ends up being most of the chimney for this little fireplace. Super easy.

First you make the fireplace. In Urique I helped make one out of rammed earth. The one we made this summer uses hardened bags of concrete. When we moved in here there was a stack of premixed concrete bags behind the barn under a tarp. It wasn’t tarped well enough, though, and all the bags were hard as….. well, hard as concrete! 

We removed the paper bags from the hardened concrete and laid out the first course in such a way as to create a fire box approximately 12 inches wide by about 16 inches deep. A second course, just like the first, was stacked on top, giving the fire area a height of maybe 10 inches. So far so good.

We used a piece of scrap angle iron for the lintel above the opening of the fireplace and then used pieces of flagstone to make the opening at the top of the firebox small enough for the bottom of the water heater to cover it.

We used old, dead concrete bags for our base but you can make your fireplace/water heater base out of just about any strong, non-combustible material. Concrete blocks, rammed earth, adobe blocks, all would work.

We took the gas burner out of the water heater, smashed down the little sheet metal legs on the bottom and then set the heater on top of the fireplace. The next step was to mix up some mortar and close any gaps between the bags and the water heater and between the bags themselves. A piece of scrap steel plate was used as the door for the fireplace.

The height of a water heater is not quite enough to get a good draft so I bought a 3-foot length of 3-inch metal chimney to extend it and improve draft. It also makes it so the smoke comes out high enough that it doesn’t smoke out a person taking a shower.

To hook it up, you need a pressurized water source. We built ours near one of our yard spigots. The pressure is the same as we get at our house so that’s plenty for this project. We took a short garden hose and connected it to a tee near the cold water inlet on the water heater. One leg of the tee goes into the water heater and the other leg goes to the cold water valve on the shower. From the hot water outlet on the heater we ran another hose to the hot water valve on the shower. We did all the plumbing using ¾” PVC which is cheap.

I bought a used shower head at Habitat for Humanity and the plumbing fittings to adapt the garden hoses to the PVC pipes. The whole thing cost maybe $40? If I had been lucky enough to find a used shower knob set, it would have cost a lot less. As it was I had to buy PVC valves to control the hot and cold on the shower and those valves were about a third of the total cost. 

The last thing we did was to make a privacy screen around the shower. We used scrap wood that was on the property and attached some wire fencing to it. Then we went down to the creek and cut a bunch of young willows and threaded them into the wire fence. We made a bench out of two big blocks of scrap wood and a floor out of a pallet. We think it came out pretty cool.

 It doesn’t take much wood or much time to get the water hot. The firebox is small so all you can put into it are twigs and small-diameter branches. It takes about 45 minutes to get the water hot and several people can shower once the water is up to temperature. Just keep adding wood to the fire and it will keep heating the water. 

Because all the plumbing is outdoors we removed the hoses and drained the water heater tank so it doesn’t freeze and break during the winter. It’s in winter mode now but, in the spring after the freezes stop, we will hook it back up and the outdoor shower will be available for the summer.