Plumbing Work & Loss of Mains Water Pressure

[Shaun Robertson]

Hi, wonder whether I could ask for a bit of advice. Not strictly DIY but I know there are lots of knowledgeable folks here who might be able to help.

We're currently having a new Vaillant condensing combi boiler fitted, in place of the old one which was beyond economic repair (and well over

20 years old)

Since the work started, the mains cold water pressure at all outlets (taps, toilet, shower) has dropped significantly, to little more than a dribble. The blokes fitting the boiler say they turned the main valve off outside the house (under the pavement) because they couldn't find the stopcock in the house (to be honest I don't think there is one!) and when they turned it back on again the water pressure had dropped. They called out Yorkshire Water as they assumed the main valve was faulty and hadn't fully opened when they turned the water back on - but YEB have subsequently been out, dug up the pavement, tested the valve and it showed more than adequate water pressure on "our" side.

The only other thing which has been suggested is a pressure activated non-return valve somewhere under the floor or under the drive which might have failed to open properly when they turned the water back on. They're looking under the remaining floorspace today to see if they can trace the route the mains pipes come into the house but so far there is no sign of any stopcock, valve or anything other than copper pipe.

Is it likely that we have a non-return valve buried somewhere under the concrete drive? :(

Could the combi boiler be interfering with the mains cold water pressure in any way and causing this problem?

An airlock or something similar caused by pressure-flushing the rads? Just a wild guess.

Grateful for your insight...

Thanks Shaun

[Stuart Noble]

Not much help I know, but do keep the ball in their (the installers') court. It was ok before you started the work, now it's not. "Well I hope you soon sort it out" kind of attitude. Dealing with the unexpected is part of the reason they charge so much. This would be a good time to put in an internal stopcock if they can find the entry point. Then at least you can narrow the blockage down and hopefully eliminate the concrete drive. My neighbour had a similar problem and, after a bit of negotiation, Thames Water ran a new plastic mains into her property. They *seem* to accept responsibility for anything up to your stopcock, even if it's a long way from the road, and you must have one because officially you're not supposed to turn off from the road. I think they must have used some sort of mole tool because nothing much was disturbed and they were gone in a couple of hours. Good luck

[Christian McArdle]

A partial or near total blockage wouldn't affect pressure after the stopcock, unless the taps were on at the time. Were they?

Christian.

[Shaun Robertson]

Many thanks Stuart.

On the one hand, my view is that it is their problem to sort out, when they started work we had perfectly adequate water pressure and they have caused the problem.

On the other, I can sympathise that *if* their story is true that somewhere under the house or under the driveway there is a faulty non-return valve which has failed, how is that their fault? A similar situation I suppose would be a TV installer plugging a television into a socket on a defective ring main, the poor condition of the homeowner's wiring is not his fault. I'm wondering who is legally responsible for the problem though.

That's a good point, thanks.

Cheers Shaun

[Shaun Robertson]

Ah, think I get what you mean. Thanks Christian.

I wasn't present when they "tested" the pressure but my two fitters were. I had assumed that they would have cut the connection to the main stopcock in the street and then let mains water flow through it to visibly demonstrate that the flow was adequate. However, if they had used some gadget to measure the pressure that wouldn't necessarily tell the full story.

In the case of a blockage caused by a faulty valve which has only partially opened the pressure would still be evident, but the flow rate much reduced. If they tested pressure and not flow rate, the fault may yet lie there.

Something to consider. Thanks

Shaun

[Shaun Robertson]

Just thought I'd post a follow-up.

Panic over. :)

After much pulling floorboards in an effort to find out exactly where the mains water supply entered the house, we finally found a stopcock...in the bathroom, boxed in and tiled over by some idiotic previous owner!

The valve inside must have moved just a tiny bit when the water was turned off in the road, bizarre to say the least - it must have been boxed in there for years, all the pipework is fitted with isolation valves so I've never needed to switch off at the mains in our 4 years here.

Most grateful for your advice :)

Cheers Shaun

[The Natural Philosopher]

# It probably is NOT your problem, but my in laws had a similar problem, except the cold tap in the kitchen worked OK. Nothing else did. This after works in the street had cut the supply off.

Traced to the fact that sediment got pushed into the till then unsuspected water softener, buried in a cupboard no-one ever opened..and which promptly blocked.

I opened the bypass, since in the 5 years of occupancy no one had ever filled it up with salt, anyway.