DIY Solar Shower Blog, v1

When we found P.D.D. three years ago, it had been kitted out with a lot of extras you wouldn’t expect on a sailboat.

One of the first projects we started was to remove anything that we knew might fail or could hinder a simple life aboard. Along with a very complex ancient NECO self-steering system, the gas boiler was among the first to go!

I hate gas, and on a boat, it really has to be respected. We had a nearly new Rinnai boiler. It failed immediately. After extensive cleaning and careful testing, it worked a few times with the water pump on full blast, then, with an almighty “boom,” it would just blow itself out again. Running naked from the shower, going from one side of the boat to the other with no blinds in the windows  just to fix the the boiler…I had had enough.

Whilst at anchor in summer, it’s pretty easy (if a touch depressing) to heat a few litres of water on the stove, pour into a plastic bottle with holes in the lid, and squeeze its contents around you in the cockpit. It gives any boaters or beach-goers a view they didn’t expect and gives you a sort of shower. Al fresco.

We had to improve the situation. A few years ago we built a solar shower for our narrowboat. It consisted of a length of garden hose coiled up under a plastic cover, a small solar powered 12v pump to circulate the water, and a 21-litre plastic container. Simply, it loops the water through the array and back into the container continuously, heating it all a few degrees each time. This whole contraption was just mounted above your head on the roof over the bathroom — or, “head,” if you like.

To take a shower, you simply opened a sprinkler end. Gravity would do its thing and you could have a luxurious free shower. Fill it up, off you go again! It was surprisingly effective, heating 21 litres up to 40 degrees in about 1hr! And surprisingly cheap at £15 for the whole contraption.

So, on a sailing boat, 21 litres is a lot: heavy and a big water demand. We could squeeze — literally — two showers out of a 2-litre bottle, so I figured we could just about get away with 2.5l for our boat shower. I searched everywhere for a solar vacuum tube. You see them sold as solar BBQ’s, and they are the same thing as the thing you see on roofs of houses. But we could find nothing. 

M.I.T. gave me one in Berlin which would cook sausages and boil 1 litre of water in 1hr! Sadly, we left it behind in Germany, which I’m still very upset about. Trawling through the online free ads, we discovered something else! Basically it’s an electric kettle, —and, even better, it’s 12v and it holds…2.5 litres! Off we went to collect it. £20 later, it was ours. (You won’t find that price new, by the way — the kettle was second hand. When it comes to discussions about prices, just assume it’s always second hand. I don’t believe in new prices!)  It’s simply a stainless steel insulated container with a spout, filler neck, and a 300w 12v element. Basically a small cheap calorifier, I think they are used for commercial builder’s vans. 

Easy to install, and quite small, it was quickly mounted above the wet-room on our catamaran, along with a 40A fuse and cable which is almost thick enough! Some hose was heated and pushed onto the spout, and a fancy garden sprinkler thing became our a shower head. I thought we would need a pump, but even from the short drop into the wet room, gravity does a splendid job. If you choose to do the same thing but don’t have space above the shower, you could mount the tank anywhere and just use a pump. 

Here comes the warning. I thought I could easily adjust the kettle to shut down at a lower temp, but after poking around the inside electronics…no. So, to get a shower temp that isn’t too hot or cold, we have to manually turn it off after about 15mins….or the water will actually boil! This has the potential to be pretty dangerous. If you go this route, a timer, a thermostat modification or both would be mandatory. We never got that far because…well, see below ***

This 12v shower system works really well. It turns out 2.5l is a little slight. It gives you a good soak and a good soap off, but that’s all  and not a lot more. It does use very little water — just 1/8th of a Jerry can of water! You can adjust it for a very hot shower if you like, and the pressure is pretty decent even if it’s mounted just above you. Plus, 15mins is really not long to wait for a nice shower. This is free energy. 

We normally wait for the house battery to recharge, which happens at about 11AM, and heat the shower after that. Whereas otherwise the excess solar we generate is wasted, with this system, we’ve had three showers in one day, with each charge using only about 8AH per charge. This might not work so well with flooded batteries. We are on lifepo4 now, and it loves huge amperage work.

I’ve since discovered there are “hot water hand washing basins” for vans that would be ideal, as well as slightly larger tanks which automatically cut off at 40 degrees! These would be perfect, although perhaps a little more pricy.

***But….just as we finished this project, something amazing turned up: a true solar thermal array that would fit on the boat! This little panel provides 175kwh peak of hot water (the temperature is subject to interpretation) and it is ten times better that the vacuum tube I mentioned earlier!

So…if you want even more free solar hot water, look for the Solar Shower Blog V2! Hopefully, it will be coming out soon.