Incoming water main hot

[nutler]

Hi all,
Here's an odd one hopefully someone can help with.
I have a customer that has hot steamy water coming from their kitchen cold tap. The tap is fed directly from the incoming main which enters the house under her back door. The kitchen floor is hot along the run of the water main (about 0.5m) also the outside steps upto the the back door and about 3m of the driveway again along the pipe run. The pipe is galvanized steel from under the sink along to the 3m point in the driveway from which plastic takes over out into the street.
If you run the cold tap for about 2mins the water goes cold, wait 10mins and run again and you have 2mins of hot water again.There are no other pipes/cables anywhere near the run of the main. This occurs even when the electricity is turned off to the property to rule out a fault.
Any ideas ?

 

[Mike Jackson]

Backflow from a neighbouring property with an unvented hot water cylinder?

 

[Anton]

I'd be getting that checked out with the electricity suppliers asap. There could be a mains supply laid underground too close to the water mains or to a gas mains supply pipe.
I have seen a gas supply pipe on fire underground caused by proximity to an electrical supply cable.

 

[bright spark]

How is the neighbours water. If it's the same, then the council may have a booster pump located nearby gone faulty and running continuously. The heat off the pump would heat the mains. Saw that happen before in an apartment block with everyone getting hot mains water.
if it's not that the. Would be an idea to have electrical supplier check area just to rule it out.

mad things happen. Once a customer that owned a creche told me they had hot water coming out of toilet when they flushed it. It ended up water supply came through service duct under floor. There was a leak on pipe in duct about 6 inches of water gathered. When heat came on it heated water like a cylinder. Water going to cistern was heated up. Flush the jax and hot water out.
Mine for the books

 

[AWheating]

Had hot water from a water harvesting tank once, faulty pump was overheating and warming the water like an immersion heater.

 

[nutler]

Thanks for the quick replies guys.
Have had electricity board out to check their end and they say all is fine.
They did find a faulty appliance in the house that put a small current down to earth which includes the water main. Thats now fixed but hot water continues to run. No sign of heat at the water meter in the street, ruling out neighbours property and pumping station.
Is it possible that the small current down to earth has set of a chemical reaction or electrolysis between the galvanized pipe and the wet ground ?

 

[Chalked]

Thanks for the quick replies guys.
Have had electricity board out to check their end and they say all is fine.
They did find a faulty appliance in the house that put a small current down to earth which includes the water main. Thats now fixed but hot water continues to run. No sign of heat at the water meter in the street, ruling out neighbours property and pumping station.
Is it possible that the small current down to earth has set of a chemical reaction or electrolysis between the galvanized pipe and the wet ground ?

Impossible.
what system is in the house? Pressurised? Tanks in the loft? Shower pumps?

 

[Chalked]

Is it a single lever sink mixer?
When all pipes are cold under the sink, run the cold only and see if the hot feed becomes hot? Might be simple as a faulty tap!

 

[Anton]

Thanks for the quick replies guys.
Have had electricity board out to check their end and they say all is fine.
They did find a faulty appliance in the house that put a small current down to earth which includes the water main. Thats now fixed but hot water continues to run. No sign of heat at the water meter in the street, ruling out neighbours property and pumping station.
Is it possible that the small current down to earth has set of a chemical reaction or electrolysis between the galvanized pipe and the wet ground ?

When you find out what's causing the hot water, make sure you let us know on here.

 

[nutler]

System update.
It is an open vented system with indirect cylinder (no immersion wired) heated from gas wall hung boiler, external circulation pump fitted near cylinder and 3 port valve. There are no other pumps in the property(no showers).
Pillar taps at kitchen sink and throughout the house. The cold is as it should be in the rest of the house and loft tank.
Sooooo bizarre !

 

[PriestyUK]

Is supply on a new meter? Get water board to remove the meter and fit a temp outlet straight off where the meter screws into. Do your check there with the water board present. That way you can rule out if its before or after the meter thats causing the problem. Just had the water board do the same but because of poor flow rate and it was down to their new taping not cutting fully into the main. And they checked this by removing the meter and screwing in a hydrant outside tap looking device. Think this is your best way to start. If fine I think you could have some gravity circulation taking place and may have a hot pipe close to main. Eliminate all heat sources and let go cold and see if you still have a problem.

Will be cool to find out what the outcome is - #Subscribed

Good luck

 

[MarkAqua]

the water main is really close to the surface and the sun is heating it up

 

[bright spark]

Do ye kno mark, ye might be right. Sometimes ye'd b picking yer brains and it's simple as that.

 

[MarkAqua]

Well I am simple

 

[JCplumb]

Turn boiler off and run hot taps until the houses hot supply is all cold, then check to see if it still happens.
If it does your problem is before the water meter!

 

[zzzjim]

Love JC plumbs ideas , will also add , Intemittent ground fault dumping current into steel main ( only one still in tact) if neighbours have had their steel replaced / isolated !
Any neighbours on economy 7 ! (heavy electric users)

If that is the case take great care cutting any pipes - big electric shock risk
( Electric board should have detected it - but then we are all human )

If heat is from sun , check how hot Black Tarmac drive is !

 

[Plumbstar Tom]

Turn boiler off and run hot taps until the houses hot supply is all cold, then check to see if it still happens.
If it does your problem is before the water meter!

This is what I would do first

 

[nutler]

Problem solved :50:
Thank you everyone for your replies and advice its nice to know that when help is needed that so many are willing to take the time to lend their thoughts on a problem.
Anyway the bit you are all interested in, the fault. After the visit from the electric board last week when they told me that their cables and equipment tested fine i was unconvinced. So I called them out again yesterday (at the risk of a heavy bill for a false call out again). This time a different team came, within 5 mins found water in their joint box on the pole, sending mains potential down the earth stay into the ground, along side the water main which carried it into the house and heating the water on the way. How bad were the first team to miss this !!
Anyway my little old lady customer now has cold water at the cold tap and water pipes at zero voltage.
Thanks again
nutler.

 

[Dotty]

Potentially bloody nasty!

Thanks for letting us know the outcome.

 

[MarkAqua]

Jesus H christ. Glad it's sorted with no injuries!

 

[kris]

It just shows you how things can go wrong without us knowing, if the water hadnt heated prompting the call out that couldve really bad, well done mate,

 

[zzzjim]

Thanks for feedback , Many accidents are preventable with hind sight.

( Currently enjoying warm fuzzy feel ,without buzzing tingle as slide hand across bare metal )

 

[mike76]

Sounds to me tap at kitchen sink is mixing! Try non return valve on hot supply to the sink cheap and easy!

 

[Dotty]

Sounds to me tap at kitchen sink is mixing! Try non return valve on hot supply to the sink cheap and easy!

It's been fixed Mike. See post #18 for what it was........

 

[Anton]

Also demonstrates the importance of temporarily cross bonding when cutting water pipes.

 

[PlumbersMate]

Sounds to me tap at kitchen sink is mixing! Try non return valve on hot supply to the sink cheap and easy!

I bet you a grand it ain't that

 

[josh]

I bet you a grand it ain't that

pillars didn't he mention? Lol.
Could be bridging the air gap between the two taps, not visible to the human eye