Strange water supply problem

[kemyst]

I have a seemingly impossible problem. I am not a plumber but I can at least understand some of it. We have just had the Water Board inspector here and even he went away flummoxed.

OK ....we have a stopcock under the sink that is stuck open - no amount of force will turn it. We need to turn off the water so that we can change the kitchen taps because they are leaking. We therfore need to stop the water to the house by turning off the external stopcock in the main road British Gas will change the internal stopcock for us but they say that the that the external stopcock is the responsibility of Welsh Water.

When they tried to turn off the water by turning the stopcock in the road, it would not turn off the water to the house so they diagnosed that the external stopcock was also faulty. TBF, they dug up the road and installed a new external stopcock. When the inspector came to check the job today and turned the water off, it did reduce the wayer pressure because no water was reaching the upstairs taps but although the water to the downstairs tap was reduced there was still a significant flow of water through it?! So we still can`t get the internal stopcock changed!

Can anyone tell me what is going on here? The mains water feed is through the back gardens of two neighbouring properties. As far as I know it goes from the road into next doors back garden and from their garden under our patio to the kitchen sink. They had a conservatory built about 2 yrs ago and Anglian did something with the plumbing then. I have no idea where the water to my kitchen tap is coming from when the mains is shut off?Any ideas would be gratefully appreciated. Thanks

 

[Chuck]

One workaround to your problem would to freeze the incoming supply and replace the internal stopcock or add a new one in series with it.

For a 'root cause' fix you'll need to do some sleuthing. E.g.

How long do you wait (how many litres run off) while the external stopcock is closed and tap is running under 'reduced pressure'? Does it eventually slow down and stop?

Do you have an accumulator and/or an unvented hot water cylinder, i.e. fed by mains pressure water rather than a cold water tank in the roof? If you have a tank in the roof, then turning the stopcock off won't affect the taps fed from the tank. If you have unvented hot water the non-return valve may be passing.

Have you asked your neighbour to see if their water meter turns when you turn off your supply and run your kitchen tap?

Does your meter turn when your neighbour uses water?

 

[snowhead]

I'm surprised W-Water gave up so easily, unless they intend to return and trace the pipework.

There's a few possibles,

There is a second supply joined on after the (new) street stop tap, maybe done accidentally when next door had the conservatory done.

Or it may have been / still is a common supply to other properties and has a large volume to clear before it stops, something Chuck is thinking of.

It could be the new stop tap feeds upstairs only and there's a second supply partially turned off somewhere for downstairs.

How old and what sort of property is it.?
Was it built on land originally owned by one or both of the neighbouring properties?

Rows of terraces used to have a single supply from the street, as it would have been cheaper, with a branch into the outside toilet and a separate branch into the kitchen.

 

[Deleted member 120897]

If your incoming main is mdpe, a squeeze off tool could be used, or as per @Chuck it could be frozen if possible. You can’t install one in series because you can’t isolate it coming in. It would need to be traced as mentioned.

 

[Warmiger]

have you had a plumber have a go with the internal stopcock?? The amount I have been to and I have undone the gland and got them going again is in the 100’s.
Other than what is mentioned above you could install an Aladdin valve on the live pipe work…
Other options are to have a run of pipe with an isolator on to outside, use speedfit pipe … cut the pipe live and install quickly.. most of the water will go outside… a wet vac is a good tool. it all depends how much of a priority the job is to you…