SBMA fire with flames rising through the coil will heat water more effectively than a bed of coals.
This ShowerCoil system is fantastic! With a fully stoked fire and a bit of practice, I could heat 4 gallons of water in just over 11 minutes and take a pleasant, warm, and long-lasting shower.
The heart of the system is an aluminum-alloy coil that heats water as it flows through the coil from an elevated bag supplying cold water. Water drains from the bag through heat-resistant silicone tubing, and a hollow braided-wire sheath protects the tubing where it joins the coil and the heat of the fire is most intense.
SBMThe heart of the thermostat is a bimetallic coil that operates a valve gate.
The hot-water tube filling the lower water bag has a small thermostat that regulates the temperature of the water by adjusting its rate of flow into one of the water bags.
SBMThe supply bag needs to be elevated about 3’ to provide the coil and thermostat with an adequate flow of water. Here it is suspended from a tripod of oars.
The two 15-liter (4-gallon) roll-top water bags are quite durable and versatile: their clear fronts and black backs make them well suited for solar-heating water; interchangeable fittings allow them to be used as general-purpose water bags; sealable roll-down tops with buckles allow them to serve as dry bags; and when equipped with the valves on the short hoses, they work as compression bags for packing bulky soft goods.
SBMWhen the ShowerCoil is used with a camp stove the sheathing over the tubes needs to be supported. The supplied Y-stand (lower right) was too short for this stove, so a twig filled in for it.
A fully stoked campfire with flames rising through the coil is required to get water nice and hot. My first fire was mostly coals, which produced just a lukewarm shower. You can also use a camp stove to heat the coil: A steel heat deflector distributes the flame around the coil, and a prop supports the sheath over the tubing. My stove heated the water in just under 10 minutes. In camps where I could make a fire, I’d prefer to do the heating with wood and save on stove fuel.
Spring CourtrightThe water bags also serve as drybags and solar water heaters.
A full water bag weighs about 36 lbs, challenging for me to manage and too heavy for me to hang up high on a tree branch. The instruction manual that comes with the kit has directions for easily lifting a full bag of heated water using ropes and carabiners, but I just used the bag half to three-quarters full.
Spring CourtrightA ratcheted clamp on the silicone tubing regulates the flow to the shower head.
One of the nicest features is the pinch valve on the shower-head hose which adjusts the levels of flow so the shower can be a luxurious rush of warm water or a prolonged sprinkling. With the valve wide open for wetting down, closed for soaping up, and opened again for rinsing, I had plenty of warm water to bathe and wash and rinse my long hair. The long hose on the showerhead makes it easy to direct the spray where it’s needed and make the best use of the water.
A hot shower is something that’s easy to take for granted at home, but it’s a great luxury in the wilderness. The ShowerCoil is a truly great outdoor shower setup.
Spring Courtright has been sea kayaking for over 15 years, leading and assisting day trips and multi-day trips in Washington and British Columbia. She has taught sea kayaking, stand-up paddleboarding, canoeing, backpacking, through the Olympic Outdoor Center, Outward Bound, Naturalists at Large, YMCA Earth Service Corps and Colorado Mountain College.
The ShowerCoil system is available from BoundaryTEC for $99.95.
Editor’s note:
I gathered some data on my own trials with the ShowerCoil. In an ambient temperature of 61°F a small fire of woodshop scraps burning under the ShowerCoil heated a full bag of water from 58° to 100° in 12 mintues with the thermostat set one click down from high. I switched bags and ran the heated water through again with the thermostat set on high. That brought it up to 120°. Hot! I added some cold water to the bag and brought the temperature down to a good level for bathing, around 105° to 110°. The full bag of heated water provided a 5 ½ minute shower with the valve wide open.
I also used the ShowerCoil with a single-burner propane cannister stove rated at 10,000 BTU. The stove didn’t provide as much heat as the wood fire and the rate of flow was much slower: After 12 mintues the lower bag was half full of water at 98°. I was impressed that the thermostat was doing its job well, dramatically reducing the rate of flow to suit the cooler fire. The heat transfer of the coil may have been made less effective by the layer of creoste that had built up after several wood-fire trials. Water flowing through the coil keeps its surface relatively cool resulting in the tarry buildup. Removing the creosote with oven cleaner, as recommended in the instructions, would improve heat transfer. To retain heat in the hot water bag I put a piece of foam padding under it to insulate it from the ground. It would be a good idea to insulate the bag further by putting a coat or a blanket over it.
I set one half-full bag, clear side up, out in the sun. In 2 ¼ hours it warmed 58° water up to 82°, not bad considering the low angle of the March sun over just the last half of the afternoon.
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Too much gear when all it takes is a sauce pan or tea kettle full of water and half a bag of cold water to get a very warm shower with a solar bag.
If you’re short on space in a boat, it makes good sense to have every bit of gear do at least double duty. A cooking pot and a solar shower bag could provide a hot shower, but perhaps not as efficiently as the ShowerCoil. If I’m correctly remembering the formula I used to use to mix darkroom chemicals to required temperatures, a gallon of boiling water added to a half bag—2 gallons—of water at 60° would mix up to 3 gallons at a toasty 110°. The temperature is good, but it takes a big pot to hold a gallon of water. I put one of my big kitchen pots on a large burner of my electric range set on high. It took 18 minutes to bring the gallon to 212°, a rolling boil. The biggest pot I take camping holds 1 1/2 quarts. Brought to a boil, it would add to 3 quarts of 60° water to create a gallon and 2 cups of water at 110°. I think that the ShowerCoil holds up well by the numbers and the system is fairly compact. A hot shower is a luxury and if you’re traveling light it’s easy to do without or make do, but if you have a bit of room to spare and plan to have campfires, 4 gallons of hot water is something to look forward to.
Christopher Cunningham, Editor, Small Boats Monthly
I always set my solar showers black side up to absorb the sun’s energy.
With the clear side up, sunlight passes through the clear surface and the water on its way to the inside surface of the black back. The ShowerCoil comes with two identical bags, so it would be easy to conduct a side-by-side test with one bag clear side up, the other black side up. I’ll give it a try and report back. In a similar test posted on YouTube, the water in the bag with the clear side up was measurably hotter.
Christopher Cunningham, Editor, Small Boats Monthly