Central Heating Leak

california356

Hi, I need some help if possible.

I recently helped a neighbour by replacing their domestic hot water tank. They had suffered with no hot water pressure because of a build up of crap inside the tank and corroded pipes.

The old tank was connected to Gun barrel central heating pipework so I isolated all the rads to reduce water loss (bungalow so all rads on the same level) and closed the one isolation valve before the coil. Then I removed the section of gun barrel to the cylinder and added a second isolation valve so that the heating could go back on with no copper tank in place.

I only lost about half a bucket of water from the heating circuit.

I turned everything back on, bled the radiators and made sure the heating was working. The ball valve for the fill/expansion tank in the attic was tied up because of a previous leak, so I manually topped up the tank.

So far so good.

A week later, I returned and plumbed in the new Cylinder, then opened the isolation valves from the central heating.

This went very well, instant hot water pressure and a neat non leaking tank.

I went back a few days later and the heating had stopped working.
I checked the header tank and it was dry, so I added water, bled radiators etc. The next day I added inhibitor, and the water level had dropped again.

This has been getting gradually worse since - it has been about 2 weeks since I fitted the cylinder.

I tried adding leak sealer and more inhibitor and replaced the ball cock so that it stays topped up and the heating remains working.

When I checked yesterday (a week after adding leak sealer) there was a steady drip from the ballcock in the loft.

So obviously there is a leak..........

The pipes are all bedded in concrete and it is old 1" gun barrel.

The pipe I removed seemed in good condition.

I know by adding new water to an old iron system I could promote corrosion, but it happened overnight which seems too quick.

I was quite rough removing the old pipe because the joins were quite seized, but cannot see any leaks in the area around the tank where I was working.

Now I am stumped because I don't not know how to trace a leak.

For my peace of mind I would welcome any suggestions about why it could be leaking or how I can trace the leak. It's not really an option to get a specialist in because I don't have €100's to splash around - I was only helping a neighbour and now feel responsible.

I am a competent plumber, not by trade but by years of experience with renovations and builds - the plumbing I installed is neat and correct.

I have read about leak detection devices. If I could at least detect the leak I could then be in a position to say ' there's your leak, I recommend getting a qualified plumber to sort it out.

Thank you in advance

slavetothegrind

the Gb is the likely culprit alright
where you removed a section of gb is there a remaining upstand into the floor?
if so dig this out and see if you disturbed a joint in the floor. very likely you did.

old cottage chances are concrete poured over soil so it just drains away

california356

slavetothegrind wrote: »

old cottage chances are concrete poured over soil so it just drains away

I think the house is about 30 years old, would that still be the case?
I don't have experience of how a leak behaves in concrete, does it just filter down through the concrete?

I've got some pictures (bad ones) of where I removed the very small section of pipe.

old.jpg
new.jpg

The section of copper at the front was already replaced and is obsolete pipe from an old back boiler no longer in place. Its the small section on the left joining the tank that I replaced.

Buford T Justice

If there is a sheet of polythene between the subfloor and the finished floor, then the leak would rise up through the concrete floor, providing the pipes are above the subfloor.

If its just concrete over earth, then the water would drain away without you even knowing it.

If its a steady drip then its a fairly substantial leak.

Not exactly the news you want to hear, but if the GB is as old as the house itself, its pretty much at the end of its live at this stage and you would nearly be better off replacing all of it.

Again, not exactly practical I understand, but worth saying anyway.

california356

Thanks for the replies - i'll have to dig down and investigate.........

nophd08

california356 wrote: »

Thanks for the replies - i'll have to dig down and investigate.........

Probably wont be far down from floor level in hotpress. As you said you were quite rough in removing old pipe so it wouldnt take much to disturb a fitting just under floor.

Carlow52

The answer IMO is in ur first post

california356 wrote: »

....corroded pipes.

....The ball valve for the fill/expansion tank in the attic was tied up because of a previous leak, so I manually topped up the tank.

Did u get an answer as 2 what the earlier leak was about

california356

Carlow52 wrote: »

The answer IMO is in ur first post



Did u get an answer as 2 what the earlier leak was about

The ball valve was tied up because the float had failed and the tank overflowed.

I am sure the leak is somewhere in the concrete, just need to find it.