I managed to get a tiping bucket sensor for free from a manufactor here in north europe. Been having some issues on how to get the arduino to register the reed valves in the sensor, but I think I have a plan there now.
Will post an update here when its complete.
The water will never freese, as its an insulated and heated location. Its just placed in a part of the house that is rented out. So I dont wanna bother the people living there with emptying the tray. Tipping bucket sensor is placed inside the original tray, and I have connected a drain pipe so that it cannot overflow.