Why does shower and sink water not drain fully when the RV is out of level?
Grey water drainage is unpressurised and the water flows purely by gravity. Out of level the design slope is lost; water sits in the tray and elbow, and smells.
Grey water drainage in caravan plumbing is unpressurised; the water flows entirely by gravity. If the vehicle is tilted away from the drain outlet the water stays in the shower tray or in a pipe elbow, leading to smells and, in the winter months, to freezing. Levelling on two axes recovers the design slope between the shower tray and the grey water tank.
How the run works
The run between the shower tray, the sink and the grey water tank has no pump. The manufacturer gives that run a small design slope; the water only drains fully as long as that slope is preserved. The grey water drainage slope is a narrow margin to begin with, because the height available under the floor of a caravan is limited. When the caravan is parked tilted on the left-right or the front-rear axis that margin is used up, or even reversed.
The job of the trap is to keep the smell in the tank from coming through; when the water level inside it falls, that barrier is gone. If the slope is the wrong way the trap does not fill completely after every use, and the smell problem starts while the water is still inside the plumbing.
What happens when it is parked out of level
- Standing water collects in the shower tray, causing slipping and staining.
- Water left in the pipes breeds bacteria and smells; when the trap dries out, the tank smell comes inside.
- In the winter months water that has not drained freezes in the pipe and can crack the elbows.
- The grey water tank level sensor reads off from the true fill level.
- Since the tank does not empty completely, it fills earlier than expected at the next use.
Which axis affects what
| Axis | Typical symptom | Correction |
|---|---|---|
| Front-rear | The tank does not empty, only a thin flow comes from the valve | Lower the side with the drain outlet |
| Left-right | A pool of water stays in one corner of the shower tray | Lower the side the waste outlet is on |
| Both at once | Both the tray and the tank are troublesome | Correct both axes together with automatic levelling |
Longitudinal tilt governs the tank and the drainage run, and lateral tilt governs the tray and the sink surface. The KTS200 measures the tilt on both the front-rear and the left-right axis and corrects it to an accuracy of 0.025 degrees, so that the drainage run returns to the position it was designed for.
What levelling does not solve
If water still stays when the vehicle is perfectly level, the problem is not the slope. A blocked waste strainer, an elbow narrowed by hair and soap residue, a dried out or collapsed trap, a blocked tank vent and a frozen drain valve all give the same symptom. If water left in the run has frozen in winter, levelling changes nothing; the run has to be thawed first. If the flexible drain hose under the vehicle has sagged, a permanent pocket of water forms there - that is an installation fault, it is not put right by slope, and it is cured by supporting the hose.
What to do in practice
When you settle in for a stop, do not disturb the order: level first, then use the water. For users who deliberately want to leave the caravan very slightly tilted towards the drain outlet on long stops, the Tare function can be set so as to take that reference as zero; how the reference is zeroed is a separate subject. The same tilt affects the fridge as well, and the tolerance is narrower there; tilt sensitivity on an absorption fridge is solved in the same parking operation. There is a simple field check too: pour a glass of water into the shower tray, and if the water runs to the waste without stopping the run is working; if it stands in a corner, the direction of the slope is wrong.
The full topic: RV automatic levelling guide