confirm water leak findings

[tellme_why]

Hello,
I have an open vented heating system with water cylinder on first floor, hot water tank in the loft and cold water tank in the loft. This is an indirect cold water supply system.
When all cold and hot water tap are closed, boiler and circulating pump off and water main supply closed, the water level of cold water tank in the loft drops about 4 inches (it's about two feet across) an hour.
So I concluded there is a leak somewhere.

I searched the leak by first lifting floorboards in key location and then by closing the water main to stop water filling noise and listening pipe noise with a metal rod.
I could not see any water inside the suspended floor but I could hear water flow noise in the kitchen hot water tap. The noise is rather faint but all other pipe do not feature any noise at all.

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Now, the suspected leaking pipe is the only one that is not routed inside the floating floor: it's routed outside in the ground and underneath a concrete - base extension. So I cannot see the water leak at all.

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What should be the next step?
1) connect an compressed air pump, pressure test the line and confirm the leak?
2) Call in a plumber and ask to confirm my finding ? How to find a plumber that is specialised in finding water leaks?

Many thanks

 

[Agile]

You will find most plumbers will not be very skilled at finding your leak.

You clearly have a good understanding of what is involved ( apart from some problem describing your tanks in the loft perhaps ).

I would suggest that you continue to investigate the problem yourself.

You have indentified a supply going under an extension floor.

My suggestion is that you isolate and cut that pipe as close to the point it disappears and insert a gate valve or full bore lever valve and leave it turned off and see if the water loss continues.

Tony

 

[dilalio]

It is likely that you are confusing the tanks in your loft!

The larger one normally supplies cold water to your cold outlets (basin, bath, wc's etc) and also to your hot water cylinder via a separate pipe.

The smaller tank is connected to your heating circuit and its level will rise and fall according to the expansion of the water in the heating circuit as it is heated and cooled. If this level keeps falling and thus, the ball valve operates to continue "topping" the tank up with water, then it is likely you have a leak somewhere on your radiator circuit. From the noise you have described, I would suspect the feed to the radiator in the extension is leaking.

Identify which tank is leaking and if it supplies heating or domestic water.

 

[tellme_why]

Thanks Agile and dilalio.
dilalio, I am not confusing the tanks. The central heating tank ballcock is quiet, no water flow. The big cold water tank ballcock is noise, water flow all the time.
Now the issue can be either on the cold water supply to taps or - indirectly - in the hot water supply line to taps. This in turn is fed by the gravity cold water tank in the loft through the heating cylinder just underneath, in the first floor.
The issue can be indeed in both cold water lines: line to cold taps and line to water heating cylinder.
I was hoping that listening to the two pipes line connected to the water tank in the loft I could spot which is got water flow (i.e. leak). However I suspect the pressure there is too small and water flow makes no noise.
So bit annoying I have to spot the noise in the ground floor (about 0.3 bars)..

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I am currently puzzled about a certain pipe arrangement to complete my understanding of this puzzle.

It seems that both "indirect cold water" and hot water are routed to the (old) kitchen, where supposedly the pipes branch out underground to the extension kitchen (where I can hear water flow noise in the hot tap).

Why the "indirect cold water was routed to the kitchen since the direct cold water (from main) is also there??? Is for supplying the washing machine?

 

[tellme_why]

I have attached a diagram of the system and the problem...

Any suggestion??

 

[dilalio]

You can identify which feed from the CWS is drawing water by putting your arm inside and finger over each outlet - you will feel the current as you put your finger nearer.

You must be losing all your hot water, if it's a leak on the hot!
Have you checked all your toilet cisterns to make sure they are not passing?

 

[Steelmasons]

You will find most plumbers will not be very skilled at finding your leak.

Why would that be???
How would you know that "most" plumbers would not be "skilled" @ finding the leak???
Tony , you are neither a qualified plumber or heating engineer...please confirm your training/certification should I be wrong.

 

[AGAS]

come on agile wtf , thats bread and butter stuff for plumbers isn't it

 

[Steelmasons]

It says it all when refering to circulator/pump orientation...."I thought all RGI's would know that"......
I guess if you're not gas registered then you have no business working on a central heating system or carrying out any plumbing works....