Had a call out today, a recently installed garden pond pump supplied by socket on ring main in garage. It appears that when the pump is switched off at socket, or by plug in timer in socket, 30mA rcd trips. I tested ring main and pump cables, all appears ok. My thoughts are pump should be supplied by double pole switch, or through a timer that switches both poles, because the neutral being permanently connected, when the phase is isolated by the switch or timer, the neutral (with the pump coming to a stop) causes imbalance on RCD and trips. Anyone agree? or am i barking up the wrong tree?