Mains water valve off but cold tap still running?

[gavcradd]

Hi, hopefully a quick question... I've recently moved and the new house has a dodgy tap in the bathroom. Before I look at it, I need to turn the water off.

I've turned off the mains valve under the sink yet the cold tap in the kitchen and bathroom continue to run - at a much reduced pressure, but still running. I did suspect the mains water valve to be dodgy, but it feels OK (it turns a decent amount, it "feels" like it closes if you know what I mean and it sounds like the water is no longer flowing when it's closed).

I have a combi boiler in the loft if this makes any difference, but I thought this just did the hit water.

Any clues before I ring a plumber? Is it definitely a dodgy mains valve or could the cold water be stored somewhere else? I have let the tap run for 5 minutes but then got worried about air locks if it did empty completely so stopped to check.

Thanks in advance!

 

[Burnerman]

More than likely, the rubber washer has disappeared from the stopcock, so it won't fully close.
What's the hot water doing?
Can you find your street stopcock, often called the 'Toby'?
John

 

[longdogs]

Does it continue to run or is it just emptying the water in the pipe work. If the boiler is in the loft, that's quite a lot of water. Try opening an upstairs cold tap to see if it speeds the process up.