This article and video demonstrate what a frost protector valve does and how to reset it in your Mobilvetta motorhome.
Your Mobilvetta motorhome has a frost protector valve that will dump water from the pipes at below three degrees Celcius temperature. This is located in a cupboard in your boot in the K-Yacht 79 and 85, however in the K-Yacht 80 it is inside the motorhome under the left squab in the rear lounge.
When your Truma heating system detects this temperature, which could result from being parked up in extremely cold conditions such as snow or a heavy frost, the Frost Protector Valve will open and dump the water from your pipes onto the ground.
This is to protect against water freezing in your pipes and causing damage. You will know this has happened if you see water on the ground under your motorhome and no water is coming out of your taps. This can also happen if the motorhome has not been used in a while.
This Frost Protector Valve needs to be manually reset so you can use your taps again
If you are parked up during a heavy frost, cold weather or in the snow and you have your hot water and heater on, the Frost Protector Valve will not open. However, at night if you turn your heater and hot water off, also turn off your water pump. The reason for this is the valve will not only dump the water in pipes but will empty your tank as well if the water pump is left on.