We use our sink quite a lot and do our bit of wild camping. It takes days of this to fill the waste water tank, and within these days we have always found a way to responsibly empty the tank.
Every so many days we will be on a campsite and there is nearly always some means to dispose of waste water there, if not a drive-over pit, than a chemical toilet drain.
We sometimes use the porta potti lower half, after we have emptied it, to drain our waste water tank: we rinse the porta potti lower half with the grey water, and so dispose of it through the same chemical toilet drain. I
n some countries (Norway) one finds often a drive over drain at the larger gas stations.
On many aires there are facilities to drain your waste water tank (the
app camper contact lets you filter them on the availability of such facilities).
If nothing else, than a sewer grid drain somewhere along the road, as Jen describes above.
Having said that, we have also come across campsites (e.g. twice in Wales) where, when we asked where the drain was, they simply said: 'don't bother, just leave the tap open and let it flow away on your pitch'....
All in all: the tank holds enough for it not to be a problem to find a responsible draining point in time before it is full.
