The right van water tank size comes from your daily use multiplied by the number of days you want between refills, then checked against the space you have and your payload. PiNCAMP, the camping magazine run with the German motoring club ADAC, puts two people at about 40 litres a day, or about 80 litres with a daily shower on board. Truma, the leisure vehicle equipment maker, says motorhome tanks hold between 40 and 200 litres. In a panel van, aim for the smallest tank that covers the gap between two water points.
1. Multiply your daily use by the number of days between fill-ups.
2. Every litre of water weighs a kilo and comes straight off your payload.
3. Then pick a shape that sits low and near the axles, and plan for draining and disinfecting.
Working out how much your van water tank needs
Sizing a van water tank starts from your own habits. In its guide to motorhome water tanks, PiNCAMP says two people use about 40 litres of water a day, rising to about 80 litres if they shower on board every day.
Those figures describe a motorhome. In a panel van with no shower, careful washing-up and bottled drinking water, your own use may be quite different. The most reliable figure is one you measure: on a first weekend away, take a container of known volume and note how much is left when you get home.
It also helps to separate tank water from drinking water. You can keep the tank for washing-up and washing, and carry drinking water separately. That choice changes how much the tank itself has to hold.
Sizing your van water tank
The sum fits on one line: daily use multiplied by the number of days between water points. Here is an example, to be replaced with your own figures, using PiNCAMP’s number for two people without a daily shower:
| Step | Example |
|---|---|
| Daily use (2 people, no daily shower) | 40 litres |
| Days between refills | 2 days |
| Volume needed | 40 × 2 = 80 litres |
| Weight of the water (1 litre = 1 kg) | 80 kg |
Keep a margin for the unexpected too: a closed service area, a broken tap or an extra day at a spot you like. Rather than enlarging the tank to cover rare cases, note your real consumption on your first trips and redo the sum with those figures, which will beat any published average. A tank sized on your own habits weighs exactly what it needs to, and the payload you save goes elsewhere, on power, gear or luggage.
That volume depends mostly on how you travel. If you call at a service area every two or three days, a modest tank is enough. Our guide to where you can sleep in a van in France covers the service areas marked with the CE24 sign, which are equipped with waste disposal points.
If you want several nights away from any tap, the volume climbs quickly, and the weight climbs with it. That brings in the next constraint.
The weight of a van water tank and your payload
A litre of water weighs a kilo, so a full 100-litre van water tank adds 100 kg, plus the weight of the tank itself. Check the maximum authorised mass on your vehicle documents and the limit your driving licence allows before you settle on a size, because the water comes off whatever payload is left after the build.
Approval rules count it too. For a conversion approved in France, the DREAL weighs the van in running order, with the tanks at least 90 % full apart from the waste tank. An oversized tank therefore cuts the payload written into the approval file, as our guide to VASP registration in France explains.
PiNCAMP notes that motorhomes up to 3.5 tonnes frequently have a tank of 50 to 75 litres. That is a useful benchmark to place your own build against: if you want more, check your payload before ordering.
Choosing the shape and position of a van water tank
For the same capacity, the shape of the tank decides where it can go. The range from Reimo, a German maker of van equipment, shows how much universal tanks vary:
| Capacity | Dimensions (mm) |
|---|---|
| 40 litres | 330 × 300 × 480 |
| 55 litres | 500 × 200 × 550 |
| 80 litres | 650 × 280 × 450 |
| 110 litres | 880 × 300 × 480 |
Some tanks are shaped for a particular spot. Reimo sells one to fit the wheel arch of a Fiat Ducato, measuring 1,150 × 645 × 260 mm and weighing 8.25 kg, priced at €214. Read product pages carefully: that one lists 80 litres of capacity while the product name says 90 litres. Always confirm the real capacity before you work out the weight.
As for position, keep the tank low and close to the axles for weight distribution. An inside tank, under the bench or in a unit, benefits from the warmth of the living space. An underfloor tank frees up room inside, but PiNCAMP warns that uninsulated tanks under the floor are exposed to frost. Our step-by-step van conversion guide shows when the water system goes in.
A fixed van water tank or water carriers: two approaches
Before you pick a capacity, ask whether a fixed van water tank is really what you need. A built-in tank connected to a pump and a tap gives you a sink that runs like the one at home, but needs a filler you can reach and stays on board whether full or empty. Removable food-grade water carriers work differently: you fill them at any tap, even away from the van, and only carry what the trip needs, at the cost of comfort and handling.
The two approaches combine well: a modest fixed tank covers everyday use, while one or two carriers act as a reserve for nights away from any tap. If your van is going through a French approval, remember that only the fixed tank is weighed 90 % full.
Planning the waste water tank as well
Every litre that goes into the van water tank eventually leaves through the sink or the shower, and planning one without thinking about where the used water goes only covers half the system. The DREAL mentions the waste tank in its running-order weighing conditions, as the one tank that does not need to be filled. That tank is emptied at service areas marked with the CE24 sign in France: size it on what really goes down the sink, mount it low too, and keep frost in mind, since an underfloor waste tank is just as exposed as an underfloor fresh one.
Cleaning and disinfecting a van water tank
A clean van water tank needs regular care. Truma, in its guide to water systems in motorhomes and caravans, says tanks should be emptied, cleaned and disinfected regularly, and also after a period out of use.
How often depends on whom you ask. PiNCAMP suggests cleaning at least twice a year. The motorhome brand Carado goes further in its magazine: every 4 to 6 weeks during the season, plus a clean in spring and another before winter storage. Carado recommends products based on hydrogen peroxide, chlorine dioxide or active oxygen, left to work for 4 to 6 hours, and describes lemon and citric acid as largely ineffective against bacteria and biofilm.
Between cleans, do not let water sit. Carado advises changing it every one to two weeks in summer temperatures. If your van has a water heater, Truma recommends heating it to 70 °C at regular intervals to stop micro-organisms from taking hold.
Protecting the water system from frost
Frost threatens both the tank and the pipework. Truma is plain about it: the fresh water tank must be emptied in winter so that no frost damage occurs. The company adds that if water is left in the water heater and freezes, the heater’s container can burst. Its models hold 5 litres for the Therme and 10 litres for the Boiler and Combi.
If you travel in winter, put the tank inside the heated part of the van. If you leave the van parked up in cold weather, drain the tank, the pipes and the water heater, as Truma asks.
Your van water tank by type of use
| Use | What to aim for |
|---|---|
| Weekends with frequent service areas | A 40 to 55 litre tank inside the van, with drinking water carried in bottles |
| Regular trips with a few nights off grid | Around 55 to 80 litres, with the payload checked |
| Full-time living or a shower on board | 80 litres or more only if the payload allows, a frost-free position and a disinfection schedule |
Measure your real use on a weekend first, multiply it by the days between water points, then set the result against your payload. After that, choose a shape that sits low, warm and near the axles, and put disinfecting your van water tank in the maintenance calendar from day one.