Some advice please..Even when the single lever sink mixer tap is put into the off position and the water flow stops, sometimes the pump keeps running. We then have to put a bit more pressure onto the lever to stop the pump. This has only started happening recently is there some type of adjustment within the top of the tap ???
There is a microswitch in the tap which switches on and off the electric pump.
When you say: "......We then have to put a bit more pressure onto the lever to stop the pump...." suggests that the fault is either in the microswitch itself (In which case it will have to be replaced) or in the actuator that works the switch. (In which case you might have to replace the tap body or make an adjustment to allow the switch to go off.
Try and see how the tap comes apart, the switch mechanism will be a simple one and any possibility of adjustment will probably be obvious.
Depends how much extra prssure you are having to put on the lever to stop the pump as to suggest either living with it, or, at worst, replacing the whole tap. Usually, this is not too bad a job.