how to find leak in sealed system?

Hi folks,

Basically my question is "Where is all the water going?". My heating has been getting noisy recently. It's a sealed system and every 6 months or so I have needed to repressurise it up to 1 bar through the filling loop and drain a couple of radiators. However, it got very noisy and on checking there was no pressure registering. Filling it took ages, as if the system was basically empty. Then, 2 days later it was noisy and showing zero again. Refilled and this time it lasted less than 24 hours. My pump then failed, which suggests to me there's no water in the system.

I checked and it's not all coming out of the pressure relief valve. The heating isn't on, there are no water stains on any of the ceilings, there's no obvious damp smell anywhere downstairs. The drain valve doesn't look as if it's leaking or anything.

Is it possible that the heat exchanger in my very old outside Kingfisher II boiler is cracked and it's all boiling out that way? Anyone have any other suggestions as to where it's going or how to find out?

Thanks

Matt

1) Why do you keep having to take rads off?

2) Has the boiler been fitted with the retro-overheat stat kit as kingfishers were never mean't to be installed on sealed systems.

If the boiler was leaking you would hear considerable noise as the water hit the burner or you would notice water on the floor.

Old lath ceilings can hold a considerable amount of water before showing any evidence. If the leaks on the ground floor it could be running straight into the ground.

Temporarily presurise to 2.5 Bar and cheak all radiator pipework (sometimes the water runs down the pipe and is not easily visible. Of course it could just blow a joint apart and you may find the leak rather more quickly.

Otherwise its time to start lifting boards.

Kingfishers of that era had to be fitted as open vented. Check with Potterton as system may be dangerous as it is not fitted according to MIs

Thanks for your replies.

I meant to say bleed radiators, not drain radiators. They fill up with air and as I fill I have to keep bleeding and the pressure drops again.

The sealed system was put in about 5 years ago as a retrofit by the company that did my loft conversion - not sure if any modifications were made to the boiler at the time. I'm about to start getting quotes for its replacement anyway so I will expedite that.

I'm going to try pressuring it up and seeing/listening to what happens.

Thanks again.

Matt

Thanks for the advice!!javascript:emoticon('')
Very Happy

I pressured the system up to 2.5 Bar and could see it visibly dropping. I went round checking all the radiators. In the kitchen I heard a hissing from under a cupboard and discovered a radiator valve from where a radiator had been removed and it was slightly open and leaking quite obviously.

Closed it properly and everything seems fine. Who knows how it got open. Must be the mice.

Thanks again for the help.

Matt

Matty I will say again- BOILER MAY BE DANGEROUS as it is not utilised as intended by the makers. Act accordingly.

Have a look at the gas valve on your boiler Matty.

You will see a very small diameter copper tube screwed into it. Where this tube screws in you should see a square shaped metal piece. In the side of this metal piece sghould be two wires leading to the overheat thermostat.

If you can't see this then the boiler has not been fitted with the overheat kit and is therefore not safe to use. The parts may still be available though.