DIY water tank from a jerry can.
We needed a water tank to feed the tap, but again buying one ready made was too expensive. As we only had a small space the largest jerry can we could fit in was 15L. After a lot of searching on the internet I found one of the correct dimensions, that would fit into our water cupboard. The obvious challenge with a water tank is to be watertight. But it must be able to let water out to the tap, while letting air in at the same time so a vacuum does not form. Equally there must be a way of getting water into the tank and air back out when filling it. All this without leaking when on the move...
Our design could easily be replicated with any plastic jerry can, of any dimensions, for almost any purpose.
Above: Our filling kit. In addition, a garden hose can be connected directly to the tank if necessary.
After much deliberation, I drilled two holes in the top of the tank, one to carry to water pipe to the tap, and the other to carry the wiring to the pump. The simple solution to waterproofing was simply to make these holes smaller than the pipe and wire that would pass through them. That way, when I forced the pipe and wire through, they push against the constraints of the hole and self seal. No silicone involved. The pipe and wire are made of semi stiff rubber, so form quite a nice seal and have so far been watertight. The holes are drilled at the top of the tank so they are never actually immersed in water, simply needing to endure sloshing as the car moves.
Above: siphoning water into the main tank from our 10L spare and the funnel backup option.
The next step was to figure out how to let air in and out, and water in when filling the tank. The jerry can I bought came with a long flexible spout attached to a screw cap. I re-purposed this, with a garden hose fitting to allow water to be sent into the tank. This fitting has a valve in it so water can't flow backwards out of the tank when sloshing about on the move. When filling the tank I just back the screw cap off a half turn to break the seal and air can escape and let water in to the tank. We fill it mainly by siphoning the water out of our 10L jerry can. We also have a funnel we can fit on the end to allow it to be filled that way if needed. The fitting on the flexible nozzle also means we can connect it directly to a garden hose if it should be necessary.
Overall it works really well in the current format, a lot of trial and error went into achieving this design. It's easy to fill and can be done with minimal spillage. It was genuinely cheap, costing a total of £45. £35 for the jerry (expensive but our dimension requirements left no room for choice) and £10 for fittings and jubilee clips. On the downside, it's a small main tank, but 15L is enough for us to drink, cook and wash up for a weekend, so it works well for that purpose. For longer trips we top it up every couple of days with the 10L jerry. We also carry a 20L solar shower, which we use for washing up and other tasks that don't require drinking quality water. On really hot days it does also produce genuinely hot water! In england, luke warm... On this note I would say that not keeping all your water in one single container is a good idea. That way you can salvage the situation if one gets contaminated with unsafe water. We only ever put known drinking quality water in the 15 and 10L tanks. Anything suspect goes in the solar shower. It's a system that has worked really well for us so far.