Which Gate Valve will turn off cold water to the taps?

[Wamus_202]

I think we have an indirect hot water cylinder, we are trying to replace a sink. However there are no isolation valves on the in-between the taps and the piping. Is there a way to turn off the cold water flow to the taps, without turning off the main water supply incoming to house ? I have found the gate valve to turn off the outgoing hot water.

But not sure where this pipe goes it to, I know it's cold water . I've tried isolating it but seems to have no effect.

 

[ShaunCorbs]

Are you sure the taps arnt off the mains as normally basins are due to drinking water and brushing your teeth