Water Systems for a DIY RV: Piping, Filtration and Capacity
When someone builds an RV, the part they research most is electrical. You never want to run out of power on the road. The part that gets overlooked in a DIY build is water: the materials, the filtration and the capacity. The more water you carry, the longer you can stay off-grid.
Start with the piping
Piping is the basis of any system, especially in a 4x4 build. Your rig is basically a house in an earthquake 24 hours a day, 7 days a week, which is hard on any structure.
I always recommend PEX-A, not PEX-B. Nothing else. The fittings are a permanent solution: the connection expands and then hugs the pipe, so nothing comes loose whether it's hot, cold or rattling. Yes, it needs a specific tool. I bought a used Milwaukee PEX tool and later sold it for $15 less than I paid. Using it for a couple of months is far better than renting one.
After 24,000 miles, 18 months and a huge amount of off-roading, I have not had a single leak.
Filtration
If you plan to be off-grid for long stretches, being able to pull safely from a river, stream or lake is a big deal. I recommend filtering both before and after the tank.
### Before the tank
Use an external filtration system, ideally with UV. That way any parasites or viruses are killed before they reach your tank. You don't want that in your system, because it is very hard to get out and it contaminates everything after it.
My own system was designed for African wells, which is some of the worst water in the world. Unfortunately the company is out of business. I have put it to the test maybe a half dozen times, over 500 gallons.
### After the tank
- Start with a pre-filter to block the larger sediment.
- Then run three filters stepping down in size. Mine are 10-micron, 5-micron and 2-micron, as far as I remember.
- Finish with an end unit that is both charcoal and UV: charcoal for taste, UV as a last line of defence.
My setup is three external filters before the tank, which I connect whenever I attach a water source, plus the post-tank chain above. I have never had a water issue past the piping and the filters.
Accumulator and pump
An accumulator is always a good idea. It keeps the water flowing steadily instead of the pump spurting and turning on and off. Put it before your pump.
Match the pump to your electrical system. Are you running 12 V, 24 V or 48 V? Get something that fits your power output, or it won't work.
Keep water and electricity apart
I'm a big believer in separating the two. On my truck the driver side is power and the passenger side is water. It evens out the weight of the vehicle, and if something leaks, my distribution panel doesn't get covered. It would take a lot of water to reach it and rise high enough to cause a problem.
Capacity
Go as large as you physically can in your space. I carry a 95-gallon fresh water tank and a 5-gallon water heater.
I chose a heater with storage rather than an instant hot water unit. Friends told me their instant systems broke a lot on the road, so I went with something more robust. I don't carry propane, so everything runs on electricity. In a smaller van I would probably still choose instant hot water, and if you have propane it is great value for the amount you use.
The short version
PEX-A piping, filtration before and after the tank, and an accumulator ahead of the pump. Add the biggest tank you can fit and keep water and power on opposite sides of the vehicle. That is how you build an excellent water system for your own rig. You can follow my LMTV build on the Destination Daily page.
