Is it something to be concerned about .It is a slight shock and no-one has died yet ! But the fact that it is when you are under the shower and in water may be a concern?
It is only a very small shock.
Additional Details added 4 months ago
It is not the house I live in and there are children living in there.
Additional Details added 4 months ago
I do not live in the house myself but there is a family and children living there
SOUNDS LIKE SOME DUMMY HAS CONNECTED ONE OF YOUR "EARTH" WIRES TO THE WATER PIPES FOR GROUNDING !!!
YES, THIS CAN BE VERY DANGEROUS GIVEN THE RIGHT CIRCUMSTANCES.
GET A SPARKY IN SOON TO CHECK !!!
It means either their plumber or their electrician is an idiot. They should have this corrected at once. It won't go away by itself. Left alone, it can only get worse and thus, potentially deadly.