Best way to find the water supply switch/tap?

Sometimes in flats and apartments the mains water isolation is by the front door. The airing cupboard will usually host the hot water tank not the incoming cold water.

Hello, since you are in a shared building the main water line isolation valve will be at the hands of the building manager. For your single property however, each water outlet such as toilet or sink will have a isolation valve attached to the pipe. It will look like a silver bit of pipe and will have a little valve, with a slot cut into it. If you get a flat head screwdriver, and insert it into the slot and turn it anti clockwise, you are able to shut off the water supply to that particular appliance. This is useful to isolate water to that applience to work on it or replace it.

Depending on the size of the block of flats the stop tap can be found anywhere, from ceiling voids, next to toilet in bathroom, under kitchen sink or in the airing cupboard, what I would recommend is running the cold tap and turning off the taps you have found one by one, this way you can narrow it down until the correct one is found, hope this helps

if its a block of flats there is usually a cupboard / plant room on ground floor where all the valved mains supplies enter the building check with the building supervisor