As John asked, what were the shocks like ?
Was it a short sharp shock, ?
If it was then maybe it was a static electric shock caused by discharging static electricity built up on your body ( harmless ) via the sink. The voltage of a static charge can be high enough to create an arc several millimetres long. It would not be necessary to touch the sink for this discharge to happen. It would discharge through a finger to the sink.
A static charge on a human body can be high voltage but very little static electrical energy can be stored and thus current only flows for a few micro seconds before the charge has been dis-charged.
A severe shock requires two points of contact with the body and a voltage difference between those two points of contact. The sink appears to be one of them, was there another one that you were touching when you touched the sink. A damp floor or work surface can be the other point of contact if there is live equipment in contact with the damp area.
Bernard put the situation very well, I thought.
In answer to the questions about the shock. It was just a sharp shock.
While you may not wish to do so, I suggest that next time you feel any “short sharp shock” when you touch
one metal object, stand still, do not make any unnecessary movement and “touch” the same metal object again.
If you
again receive a similar shock, it is
not static electricity. (
There is probably a fault, which needs to be investigated and corrected by a competent person.)
If you do
not receive a shock the second (third, forth …..) time, it
is (just) static electricity.
If the weather (or the house) is warm and dry where you are and you are wearing clothing made of synthetic material, it is likely that
you are generating a "charge" as you move about - and it does not take much movement.
Many years ago, I encountered a situation when working in a newly refurbished office building where I received a "shock" each time I walked across the carpeted floor and touched the "lift button". The capet was made of synthetic fiber and the soles of my shoes were also a synthetic material.
To obviate the problem i developed the habit of touching the button using a coin, key or other metal object.
The discharge still took place and, under the right conditions, it could be seen or heard. However, I then did not feel it, because it took place at the edge of the metal object(s).