I have a double socket fitted to the back panel in a cupboard under my sink. One socket has a sink waste disposal unit plugged in and the other has my dish washer plugged into it.
I am getting a low voltage current from the tap and the waste drain, (approx 3 volts). This is just enough to make yoou pull your hand away when touching either the bottom part of the tap or the metal drain hole.
There is no current when just the waste disposal unit is plugged in and switched on. However when the dishwasher is plugged in and switched on the problem returns. The dishwasher does not have to be running for the problem to resume as just supplying current to it is enough.
The sink is a resin compound variety, so the metal components are the taps, pipes a waste drain fittings.
The double socket is on the ring main which has a spur nearby to a blanked off plate which used to feed boiler controls but has now been disconnected due to a new boiler being resited elsewhere.
I am not getting this problem anywhere else in the house.
Your help and advise would be appreciated.