Hissing sound in cold mains pipes

[stanwaw]

Hi everyone,

I received a higher than usual water bill last week. I can now hear a hissing sound in the cold mains pipe on the ground floor of a 1970's terraced townhouse (had to switch off several appliances, like freezer and NAS/hard disks, to sense this noise). There is no history of leaks inside the house or outside during my ownership the last 10 years and I would say the property has been maintained well.

The house is dry all over, e.g.:
- checked all taps,
- valves,
- toilet flushes,
- loft tank, etc.
No signs of leak anywhere, inside or outside the property, no damp walls/floors, absolutely nothing and the water flow and pressure seem OK. That's during normal occupancy for a family of 4.

I have consumed many related and very useful threads in this forum which advised to do further checks with the stop valves:
- With all appliances off at home the water meter is active.
- When I switch off the home stop cock (right at the entrance on a straight line, ~25ft from the Thames Water meter), I can still hear the hissing noise, but I have the feeling it faints a little. The meter still shows activity.
- When I switch off the valve at the pavement, the sound is gone completely. The meter still clocks, of course much lesser now, but it doesn't fully stop as I would have expected.

Would this indicate some sort of leak on the service pipes under the driveway (laid between the meter and the home stop cock)? If there is a leak, where does this water go? There are no signs of puddles, or anything else on the driveway to indicate a leak... This is all very puzzling.

I would appreciate further advice.
Many thanks,
Stan.

 

[terryplumb]

Sounds like you have an underground leak .if the stopcock inside your premises is off ,as well as the external stopcock ,and your meter is still recording water usage,you need to contact your supplier to investigate.

 

[stanwaw]

Thank you terryplumb, I have already reported this to the water utility; they're sending their contractors end of the week. I would have expected at least the water meter to stop recording completely when the external stopcock is off. Is this normal?

 

[terryplumb]

No it's not normal ,are you sure the external stopcock is being fully closed ??

 

[Deleted member 267285]

As per @terryplumb - make sure your external stopcock is off fully, try opening kitchen tap, if it continues to run, I suspect the boundary (external pavement) stopcock is letting by.

 

[stanwaw]

No it's not normal ,are you sure the external stopcock is being fully closed ??

Thanks @terryplumb and @CBW, I was pretty sure it was fully closed, although I was being over cautious not to cause any damage. I guess I'll wait for the utility contractors end of the week to ascertain the valve/meter part.

What's the most cost effective way to approach it, if any leaks are suspected under the driveway? I guess insurance would need some sort of evidence (which I don't have yet as everything is dry), or specialist track & access, first?

I curiously phoned up a couple of plumbers and got rather high quotes (~£7,000 - £7,500 incl of VAT) for full replacement of service pipes.

It is getting a bit stressful now.

Thank you again for all your hints.
Stan.

 

[Hugh Jaleak]

'Listening' is still the tried and tested way for checking for leaks on water supply pipework, the Water Company People use Listening Sticks, basically a wooden road with a cup on the end to listen for the tell tale sound of water leaking from pipework. By the sound of things you have a leak on your property, so afraid it will probably be down to you to fix, but if the Thames Water stoptap is letting by, they should replace that FOC.

Where I am confused is, if the internal stoptap only dulls the noise a little then I'd have to say the leak is past that point, obviously shutting the Valve will slow the flow (and leak) down, but if the Valve is not shutting off completely it will still allow water by and the leak will still be active, if not as strong as previously. Shutting down the external Valve should stop the flow completely, the fact the meter is still showing signs of movement, (and they are very sensitive) would indicate that Valve is not shutting completely either.

Is there any however small, flow from the lowest cold tap in the property with the internal Stoptap turned off? Also, definitely no water trickling down the back of a toilet pan from a faulty flush valve? (Has been known to catch people out, some food dye in the cistern will give any leak away.)

You can self lay a new service from the boundary to the property, if the new style Meter box/Stop Tap is already in situ, you may even be able to connect that end yourself. Speak to a Groundworks Company as they may be better placed/equipped to dig rather than a Plumber.

 

[old duffer]

This happened to my neighbour last week. Water company came out and checked the main stop cock and replaced it. Then said the leak was definitely on her property. They gave her list of a few companies who could resolve the problem for her and then told her she had 14 days in which to fix it or they would have to come back and do it then charge her. Best price she has so far is £6000...and she now has only 1 week remaining.
Moral of the story is make sure you have a plan in place or it will get expensive very quickly.
Close house stop cock and drain taps so no water in house....if water still running then its before the stop cock i.e. external
sensitive listening devices are not expensive from ebay, around £50. Considering the massive amount you are going to pay, they would be a good investment for you.

 

[stanwaw]

Where I am confused is, if the internal stoptap only dulls the noise a little then I'd have to say the leak is past that point, obviously shutting the Valve will slow the flow (and leak) down, but if the Valve is not shutting off completely it will still allow water by and the leak will still be active, if not as strong as previously. Shutting down the external Valve should stop the flow completely, the fact the meter is still showing signs of movement, (and they are very sensitive) would indicate that Valve is not shutting completely either.

I've tried my best to switch off the pavement stop valve and I think I managed to, as others have pointed out above. I've been reluctant to tighten it too much; it's only a plastic head as far as I could tell and things could break. I'll leave this to the water company to repeat when they come around on Friday.

Is there any however small, flow from the lowest cold tap in the property with the internal Stoptap turned off? Also, definitely no water trickling down the back of a toilet pan from a faulty flush valve? (Has been known to catch people out, some food dye in the cistern will give any leak away.)

I'd say a firm 'No' is the answer here. What I did was I switched off the internal stop cock this evening and drained the house. Opened all taps that I know feed directly from mains cold, flushed downstairs toilet, etc. Not a drop after a while. But I could still hear the hissing in the cold pipe.

You can self lay a new service from the boundary to the property, if the new style Meter box/Stop Tap is already in situ, you may even be able to connect that end yourself. Speak to a Groundworks Company as they may be better placed/equipped to dig rather than a Plumber.

That's useful to know @Hugh Jaleak, thanks, I have indeed a fairly new meter box, installed in 2012.

 

[stanwaw]

This happened to my neighbour last week. Water company came out and checked the main stop cock and replaced it.

I take you mean the external stop cock on the pavement? I was under the impression the water company would not replace any stop cock on your side of the boundary?

Then said the leak was definitely on her property.

I got a little confused here, @old duffer. They changed your neighbour's main stop valve on the pavement without testing which side the leak was on? Sorry if I misunderstood you...

They gave her list of a few companies who could resolve the problem for her and then told her she had 14 days in which to fix it or they would have to come back and do it then charge her. Best price she has so far is £6000...and she now has only 1 week remaining.

I'm getting about the same quotes in London, £6000+VAT.

Moral of the story is make sure you have a plan in place or it will get expensive very quickly.

Thames Water said they have a process for customers to claim costs for leaks. To quote the guy I spoke to: "We can help you with that as it was spotted and reported early". They basically calculate the wasted water and I'd have to file a claim through their billing dept. Sounded reasonable.

Close house stop cock and drain taps so no water in house....if water still running then its before the stop cock i.e. external

Yes, see my response above, I did this and could still hear the hissing noise in the cold mains. Water meter recording usage. If this is suggesting a leak on the service pipes I cannot explain where this water is going! My estimate is about 5 cubic meters per day now. And everything is dry.

sensitive listening devices are not expensive from ebay, around £50. Considering the massive amount you are going to pay, they would be a good investment for you.

Any experience or recommendations would be very welcome, I'd appreciate a link and I could take it from there.

Many thanks everyone for your responses. Stressed already.
Stan.

 

[oldbutnotdead]

Best get your digging boots out. Or find your household insurance, see if it covers leaks in the supply pipework (unlikely but worth a look).
The real pain will be if you have concrete floors, no path up the side of the house and no cold water pipework in the front of the house- in that case you might want to look for a moling contractor.
Just before you start digging, worth checking with your electricity, gas and telecoms distributors for locations of their services in your front yard.

 

[Razor900]

If you find the leak there is no need to replace the whole service just fix it...

 

[old duffer]

I take you mean the external stop cock on the pavement? I was under the impression the water company would not replace any stop cock on your side of the boundary?


I got a little confused here, @old duffer. They changed your neighbour's main stop valve on the pavement without testing which side the leak was on? Sorry if I misunderstood you...


I'm getting about the same quotes in London, £6000+VAT.


Thames Water said they have a process for customers to claim costs for leaks. To quote the guy I spoke to: "We can help you with that as it was spotted and reported early". They basically calculate the wasted water and I'd have to file a claim through their billing dept. Sounded reasonable.


Yes, see my response above, I did this and could still hear the hissing noise in the cold mains. Water meter recording usage. If this is suggesting a leak on the service pipes I cannot explain where this water is going! My estimate is about 5 cubic meters per day now. And everything is dry.


Any experience or recommendations would be very welcome, I'd appreciate a link and I could take it from there.

Many thanks everyone for your responses. Stressed already.
Stan.

1.You got that right
2. Yes, you got that right. Default position apparently for that team
3. They have you over a barrel as it's time limited
4. Water meters don't actually save money for us, in fact, they cost more.
5. Yes it is. Water runs down the path of least resistance. In my neighbours case, I had alerted her to water in my garden and asked if she had left a garden hose running. The water emerged some 100m from the leak point having travelled under her home before hitting my garden
6. Water noise travels which is what makes it easier to detect leaks. Water can go anywhere. 500 litres per day is a big deal
It's going to be a home insurance claim so I'd call your insurer and see if they have a company they recommend (deal with already)

 

[stanwaw]

5. Yes it is. Water runs down the path of least resistance. In my neighbours case, I had alerted her to water in my garden and asked if she had left a garden hose running. The water emerged some 100m from the leak point having travelled under her home before hitting my garden

Many thanks @old duffer, that's very useful info. I'm tempted to walk down the road to look for puddles and streams...

6. Water noise travels which is what makes it easier to detect leaks. Water can go anywhere. 500 litres per day is a big deal
It's going to be a home insurance claim so I'd call your insurer and see if they have a company they recommend (deal with already)

I've phoned them up already, they cover track and access, plus repair up to £5k. But they need evidence of a leak to get me through to claims, which I cannot provide as there isn't a leak yet! They advised to wait for Thames Water's report and take it from there... such a pain.

BTW, I was browsing at some listening equipment on the net, there are some which you can rent on a weekly basis at rather reasonable costs. They are specialised devices which may need training though... any advice?

Leak Detection Equipment Hire Next Day Delivery | Hire | Sunbelt Rentals | Test & Monitoring

Browse our full range of Leak Detection equipment from brands such as SebaKMT and UE systems - available with next day delivery

www.inlec.com

 

[Lower]

I would check with your neighbours if their water goes off when you turn off the stopcock in the street. Its possible that there is a shared feed somewhere, particularly on a terraced house.