Underfloor leak in CH

[B91]

CH system (circa 1955 and originally gravity fed) has 1" steel pipework feeding into larger diameter steel pipes in sand filled trenches under concrete floor before returning to Vaillant EcoMax 835 boiler.

The system has a slow leak which went undetected during boiler installation in 2005. I estimate the leak to be roughly 500ml/hour and it hasn't changed materially since installation. There is no surface evidence of this leak and it would be unthinkable to start digging up the floors to find and repair it so I'm looking for some other solution.

It was once suggested to me that radweld might fix it, and it might, but I've no experience of it, and do wonder whether it might affect the Vaillant's heat exchanger in any way.

Any thoughts on this, or other possible fixes?

 

[Boilerman2]

Fernox Internal Leak Sealer might help, but 500ml/hr is quite a sizeable leak! I'm supprised that someone fitted a HE Boiler onto 1950's Iron pipework in the first place!

 

[Agile]

If its really leaking that much and you are adding 12 litres per day then the new oxygen will be rusting the inside of the pipes very badly.

In my view its a seriuous situation which will need some serious work on it.

Tony

 

[B91]

You are right, it should not have been fitted in the first place. The installer said he had leak tested it, but clearly he had not as it stopped after a day or so due to pressure loss. He subsequently installed a pressure control valve and a non-return valve and it has run continuously since.

I shall try the Fernox and keep my fingers crossed. Let you know, and thanks very much for the suggestion

 

[B91]

Fernox Internal Leak Sealer might help, but 500ml/hr is quite a sizeable leak! I'm supprised that someone fitted a HE Boiler onto 1950's Iron pipework in the first place!

Over the moon here! Gave the system a double dose of Fernox yesterday and this morning the telltale blade on the meter, which shows even the slightest usage, is rock steady for the first time in five years!!!!!

Thank you so much

 

[B91]

More than two years now and the Fernox has done the job. The only loss now is a very gradual fall in average pressure over a few months due I guess to tiny losses from valves and bleeds. Opening the water supply to the system there is no perceptible flow and I just leave it open 2-3 hours to restore normal working pressure. I've added inhibitor too of course.

If Fernox hadn't worked I would have been facing a major problem - large house, concrete raft floors, and a leak somewhere beneath. It's cost me about £70 to fix it. Could have been £20k or more