How much water do you actually need in a campervan?

It sounds like one of those questions that ought to have a nice simple answer. It doesn’t.

In our first campervan I kept the water system deliberately simple. I wanted fresh water connected all the time, but I also wanted to be able to lift the container out and take it to the campsite tap without dragging the pump and half the plumbing with it.

So I used a removable water container, a little 12V submersible pump and quick-release connections. Simple, easy to live with and it worked.

Would I still do it that way? In a small campervan, yes. But if you have a shower, want to spend several days away from a tap or simply hate carrying water containers around, a fixed tank starts to look much more attractive.

So rather than pretending there is one “best” campervan water tank, here are the options I would actually consider.

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A removable water container – still my favourite simple solution

For a small campervan, I would start here.

A container around 10–20 litres is big enough to be useful but still small enough to carry to a tap. You can see how much water is left, take it outside to clean it and replace the whole thing without dismantling the van.

A current example is this Clearcut 20L campervan fresh-water container. It is made for campervan and motorhome use and the lid is designed so a submersible pump can be fitted through it.

Twenty litres of water weighs about 20kg though. Carry one from the far end of a campsite and 20 litres suddenly feels like plenty!

This is how I did ours

On our Transit I drilled the container lid for the water pipe and pump cable, left the submersible pump inside and fitted quick-release connections. I could then unplug the container, lift it out and take it straight to the tap.

It was one of those little jobs that worked well enough that I never felt any urge to make it more complicated.

You can see the original build here: our simple campervan fresh-water system.

If I were putting together the same sort of system today, a Whale 12V submersible fresh-water pump is the sort of pump I would look at. The current model is made for fresh water and takes 10mm or 12mm hose.

For drinking water I would also use proper food-grade hose rather than whatever happened to be lying around in the workshop. This 10mm food-grade drinking-water hose is currently sold specifically for caravans, motorhomes and campervans.

Just make sure the hose size matches the pump and fittings you choose.

What about a fixed water tank?

A fixed tank makes sense when you want more capacity and don’t want to carry the whole water supply to the tap by hand.

There are three main places I would look at putting one.

Inside the campervan

Under a seat or bed is often a good spot. The tank is protected from road dirt and, because it is inside the living space, it is less exposed to freezing weather than one hanging underneath the van.

A current example is the Fiamma 70L onboard water tank, which is intended as an internal/under-seat motorhome and campervan tank.

Seventy litres sounds lovely compared with carrying a 20-litre container around, but remember what is inside it: roughly 70kg of water when full. That needs to make sense for the van’s layout and payload. Whatever tank you choose, it needs proper support and restraint; with a larger tank I would also think about where that weight sits relative to the axles.

Over the wheel arch

I quite like this idea because it uses a shape that can otherwise be awkward to do much with.

The Wydale 24L wheel-arch tank is a good example. It is shaped to sit over a wheel arch, has six M8 mounting inserts, and specialist tank suppliers list this model as suitable for potable drinking water.

Twenty-four litres is not enormous, but that may be exactly the point. You gain a useful fixed water supply without giving up a huge lump of storage space.

Before buying any shaped tank, remember to allow room for the outlet, filler, breather and pipework as well as the tank itself. I would also want a proper inspection opening. If you can never get inside the tank, cleaning and checking it later becomes far more awkward than it needs to be.

Underneath the van

An underslung tank keeps the inside of the campervan free and can give you much more capacity.

This is the option where I would be least inclined to buy a generic tank simply because it looked about the right size online. Exhausts, chassis members, spare wheels, cables and brackets all compete for space underneath a van, so a tank designed for the actual vehicle can make life much easier.

If we were building another van and wanted an underslung tank, I would start with the specialist campervan suppliers and then compare prices rather than forcing an Amazon choice into the article.

I would also look very carefully at ground clearance and what is already underneath the van. Owners have found that some tanks sit lower than expected or end up uncomfortably close to wheels, heaters or other fittings. A tank that technically fits is not necessarily a good fit.

And one detail I would definitely sort out before the tank went anywhere near the van is the drain. If the only way to empty it is to crawl underneath the middle of the vehicle every time, you will quickly wish you had put the valve somewhere easier to reach.

How much water do you actually need?

This depends far more on how you camp than on the size of the van.

For two people using water mainly for drinks, cooking and washing up, a removable 10–20 litre container may be plenty if you normally have easy access to a tap.

Add a shower, several days off-grid or a family using the van and the amount disappears much faster.

As a rough starting point:

• 10–20 litres – small campervan, simple sink and regular access to a tap.
• 20–50 litres – a useful middle ground if you want more capacity without carrying a huge amount of water.
• 60–100 litres+ – larger conversions, showers or longer periods away from easy refilling.

They are not rules. If you already use a campervan, your own water use is a much better guide than somebody else’s calculation on the internet.

There is little point designing the whole conversion around 100 litres if 30 litres normally gets you comfortably through the day. And having a 70-litre tank does not mean you have to fill it with 70 litres for every trip. Carry the water you are likely to need rather than hauling dead weight around for no reason.

Don’t forget how you are going to fill it

This is easy to overlook when you are concentrating on where the tank will fit.

With a removable container, filling it is obvious – take it to the tap. With a fixed tank, you need to get the water to the van.

That could mean a hose through an external filler. Lockable campervan water inlets are readily available; this vented lockable fresh-water filler is one current example.

Even with a fixed tank I would still keep a small portable water container in the van. There will always be a campsite where the tap is just far enough away to make your carefully planned hose completely useless.

I would also carry my own food-grade filling hose rather than relying on whatever hose happens to be lying beside the tap. A 10m flat food-grade caravan/motorhome filling hose is one current example. Keep your hose clean, let it drain and dry before storing it if you can, and include it when you periodically clean the rest of the fresh-water system. A clean tank is not much use if you fill it through a dirty hose.

Submersible pump or pressure pump?

For my simple removable-container setup, I would use a submersible pump again. There is very little to it and it does exactly what is needed.

Once you have a larger fixed tank and several outlets, an external pressure pump starts to make more sense. It keeps the pipework pressurised, so opening a tap starts the pump automatically.

A typical campervan example is the Shurflo Trail King 10 12V pressure pump, which is designed for caravan, motorhome and boat water systems.

That is a better fit for a more substantial installation. I certainly wouldn’t fit one just to make a simple sink system look impressive.

Cleaning and sterilising the water tank

This is one job that is very easy to forget because, unlike an empty gas bottle or flat leisure battery, a dirty water tank doesn’t always announce itself immediately.

If the system has been sitting unused for a while, particularly over winter, I would clean and sterilise it before putting it back into regular use. The same goes if the water develops a stale taste or smell.

You can buy treatments specifically for caravan and motorhome fresh-water systems. Puriclean water-system cleaner is one current example; it is sold for cleaning and sterilising the complete water system rather than just wiping out the tank.

That word system matters. The tank may be spotless while stale water is still sitting in the hose, pump or pipework. When I clean a system like this I want the treatment to reach the parts that actually carry the water, not just slosh around in the bottom of the tank.

Owners have all sorts of routines for how often they do this. A common one is at the start of the season or after the van has been standing unused, but I would follow the cleaner instructions and the instructions for any boiler or water heater fitted to the van rather than inventing a universal timetable.

Use the treatment at the concentration and contact time given on the product, run it through the system as directed, then flush with clean water. If you use a separate filling hose, it is worth keeping that clean as well.

This is another reason I like having decent access to the tank. Anything that makes cleaning awkward tends to get cleaned less often!

Winter – don’t leave the system full of water

If the campervan is going to sit through freezing weather, empty the fresh-water system.

Water expands when it freezes. Leaving it trapped in a tank, pump, tap, pipe or water heater can turn a simple bit of winter preparation into an expensive spring repair.

At the end of the season I would drain the fresh-water tank, switch the pump off and open the taps to help the system drain. On a fixed system, use its drain points as well and make sure water is not left trapped in the pump, filters or low sections of pipe. If the van has a water heater or boiler, drain that as well using its own drain arrangement. Truma’s water-heater guidance specifically says its water heaters must be completely drained when there is a risk of frost.

On a simple removable-container system like ours, winterising is wonderfully uncomplicated: take the container out, empty it, drain the pipework and leave everything dry. I cover the other seasonal jobs in preparing your campervan for winter.

A large fixed installation needs a little more thought when you build it. A proper low-point drain is well worth having because you do not want to discover in December that the only way to empty the tank completely is to remove half the furniture.

If I were choosing again

For a small campervan with a sink and basic water needs, I would still use a removable container and submersible pump. It is difficult to beat for simplicity, and ours proved that you do not need an elaborate system to have running water in a campervan.

For a larger conversion I would choose the tank position before worrying about capacity: inside if I wanted winter protection, over the wheel arch if space was tight, or underneath if preserving interior storage mattered most.

Then I would make sure I could fill it easily, clean it properly and drain it completely in winter.

Get those bits right and the number printed on the side of the tank becomes a lot less important.