Garden tap stopped working...?

[SidJames]

Folks,

Daughters new'ish build house has an outside tap to rear garden. It was working fine last used, albeit the estate suffers from dire water pressure. Today open the garden tap wide and barely a dribble.

As it's a new build and not an old house like my own I set off on a voyage of discovery under the kitchen sink.

Main stop cock. It's on. Check
Water pressure valve and a filter after stopcock....ohh that's new!

Pipe comes off the back of the filter and round to under sink where it disappears behind the back wall of cuboard....I assume to feed the kitchen sink cold, and the outside tap.

Kitchen cold works fine, as do all other cold taps in the house.

Here's also a new thing to me, a small stopcock on the cold feed to outside tap......AND what looks to be a separate shut off valve above it? This however has a nut closing where you might find the valve screw???

Turned the tap stopcock off, went outside and unscrewed the tap off the wall, turn stopcock back on expecting niagra falls....nothing.

Now I am lost! What does that pretend shut off valve do?

Pictures here.







the last two pictures are upside down!


Just to be clear, no faffing or other work was done between it working fine, and drying up.

thanks in advance.

[Magic919]

Maybe a non-return valve. Perhaps it's faulty.

[SidJames]

It appears to be a double check valve, thanks for the prompt.

http://www.screwfix.com/p/15mm-double-check-valve/...

Still not sure what they do, and are they prone to both shut off?

[finlo]

Outside taps have to have a non return valve by law, in case a hosepipe is laying in some stty water and the pressure was to drop sufficiently to draw stty water back into the system contaminating the whole area.

[jagnet]

SidJames said:

Still not sure what they do, and are they prone to both shut off?

They can jam shut, especially if the pipework on the tap side has frozen up at any point increasing the pressure in the pipe and forcing the valves back into their seats. I would try to remove it and see if that's the issue. You should be able to blow through it in the flow direction, if you can't then it'll need replacing unless you can free the check valves up. With the check valve off you can also (carefully) check that the stopcock is opening.

Before doing that check that the outside tap itself doesn't have any check valves built in. With an internal double check valve fitted it shouldn't, but that doesn't necessarily mean that it hasn't especially if it's been replaced at any point. If it does have check valves then it should have a test point visible underneath like the one in your double check valve:



Even if there isn't a check valve in the tap, before messing around with the internal one I'd unscrew the outside tap from the backplate elbow and see if water then flows to make sure that it isn't the tap that's at fault. You'll need to wind some fresh PTFE tape onto the tap thread when refitting.

[SidJames]

thanks all.

scabby builder/plumber threw so much paste in the bottom it gunked the valve up. wasn't helped with 2 bar trying to push it open.

replaced, know all good.