Grey Water Drainage Slope
Grey water is the used water coming from the shower and washbasin, and it empties from the tank by gravity alone. Keeping the drain outlet at the lowest point of the tank depends on the vehicle being level. Even a few degrees of tilt in the opposite direction leaves water at the bottom of the tank and causes odour to develop quickly.
There is no pressure pump on the grey water line; the water flows from the tank to the drain valve by slope. If the vehicle is tilted, the low corner of the tank may not be where the drain outlet is, and the water in that corner does not drain.
- Odour: the soap and organic residue left in the tank enter bacterial breakdown quickly.
- Measurement error: the level sensors are affected by tilt as well; water can remain inside while the tank appears empty.
- Shower tray: if the drain outlet is offset to one side, water collects at one edge under lateral tilt.
- In winter: water left in a tank that has not drained fully can freeze and damage the tank and the valve.
A practical habit: level the vehicle before emptying the tank, and leave the valve open for a while after emptying is finished. In winterising, complete emptying is even more critical; if necessary, giving a temporary slope that lowers the drain side somewhat reduces the residue. Automatic levelling makes this operation repeatable at every stop.
Context in which this term is used: RV automatic levelling guide