The old sensor was digital, but the new one delivers an analogue voltage, so needs to be connected differently at the other end. This only involved moving one wire, but I had to partially dismantle the cupboard at the back door to reach its new location. It all seems to work and we are getting a reading. The previous reading was 135L, the new one is 35. Have we gained an extra 100 litres of waste capacity? I suspect the reading may represent 3.5 volts, where 10v means the tank is full, so should be read as 35%. Rob will probably advise, but I will monitor reported levels over the coming days, and also next time we empty the tank.