Washing-up is often the most regular grey-water source. Amounts change greatly depending on whether you cook daily and how much crockery you use.
Spaziou tool · Water · Weight · Supply duration
Size your grey-water tank with room to spare.
Calculate how long your tank takes to fill or the capacity needed for a chosen duration. The result combines actual usage, a safety reserve and the water weight you carry.
Calculator
How to interpret the result
Do not simply choose the largest tank. Find the right balance.
A camper with 100 L of fresh-water capacity does not automatically need a 100 L grey-water tank. Some water is drunk, used for cooking or used outside; only some reaches the tank. The share depends on your travel habits.
40–60 Lgetaways and light use
60–90 Lcouple with mixed use
90–120 Lmore shower use or longer duration
+120 Lcheck weight and installation position
Spaziou rule: size it first from consumption and actual emptying frequency. Then check fit, mass and axle-load distribution. A larger tank may be less useful than emptying more often.
What enters the grey-water tank
Count only what actually enters this tank.
Showering has the greatest effect on tank size. Leave it out if you shower elsewhere.
Add an allowance for daily discharge if it also enters this tank.
Chemical or dry toilet waste is not grey water, except in specifically designed combined systems.
It sets an upper limit on possible grey-water volume, but not all fresh water becomes grey water.
Exposed valves and pipes can freeze before the tank itself.
Before installing
Plan capacity, weight and installation position together.
Water moves from the fresh-water tank into the grey-water system as it is used. In practice, both tanks may contain water at the same time, so account for both when checking weight.
Frequently asked questions
Should I leave spare tank capacity?
Yes. Leaving spare capacity avoids relying on 100% nominal volume and allows for slopes, inaccurate sensors or delayed emptying.
How much does a full tank weigh?
About 1 kg per litre of water, plus the tank, brackets, valves and pipes.
Can my grey-water tank have the same capacity as my fresh-water tank?
You can, but it is not always needed. First estimate the share of fresh water that actually enters the grey-water tank.
Where should the tank be installed?
Choose a protected position compatible with the vehicle, with access for emptying and maintenance. Check ground clearance and weight distribution.