Fresh water tank starts draining at around 40%

[DoupageCoupage]

Hello everyone, new owner here.
When filling up fresh water tank, I cannot go over 40% capacity. Once reached, the water comes out through what looks like a dark, very short metal pipe (2cm diameter, 2cm long) underneath the car. My best guess it's an overflow valve. That made me think that the display showing 40% could be wrong, but after having a shower I was down to 5%, and then, after opening taps, the water was quickly gone.
Any ideas?

 

[Mr T]

Hello everyone, new owner here.
When filling up fresh water tank, I cannot go over 40% capacity. Once reached, the water comes out through what looks like a dark, very short metal pipe (2cm diameter, 2cm long) underneath the car. My best guess it's an overflow valve. That made me think that the display showing 40% could be wrong, but after having a shower I was down to 5%, and then, after opening taps, the water was quickly gone.
Any ideas?

Have you checked the “wheel” (black shut off valve) on the top of the water tank is fully closed? Clockwise.
Found under the bed nearest the sink.

 

[AndrewCook680]

I think the wheel that closes tank has too drain settings, the first when unscrewing it is drain and leave a 20% water in tank and turn again and it drains fully
Maybe yours set to the partial drain mode.
I find the control panel water level gauge is way off. I reckon when it’s 60-70% on panel you have 50% water left

 

[DoupageCoupage]

Thank you both. The wheel seems to have three settings indeed. One is 0 litres, second one is 20 litres (the one it was set to) and there's also the full 110-litre setting.
In the meantime, I read that the fresh water sensors are a bit dodgy, and that is exactly the case with mine, therefore the 20-litre setting was indicated as around 40-45% tank full on the display. Today, I filled the tank using 15-litre water container and it was showing 100% already at around 70 litres. I will try to get it replaced under warranty.

It made me think about the grey water tank sensor now. Assuming it's also skewing indication, when I reach full tank it will start overflowing somewhere underneath the car?
I guess it's difficult to gauge its level any other way?