Cast Iron Raditor - Tackling Pin Hole Leaks in a large system

[meb97me]

We have quite a large combi boiler central heating system 15 radiators (13 large cast iron rads) and one of the radiators we've just had refurbished (blasted & powdercoated) has a number of pin hole leaks. The leaks aren't sufficient that its dripping but in operation we're getting tiny black bubbles coming from a couple of the joints.

Whilst fitting the rad and refilling the system I put in 2l of leak sealer as a precautionary measure but I have no idea as to the water volume of the system (but it does take a good while to refil once drained down) so I have no idea if that was enough. The systems been running for a couple of days now but I'm still getting small pinhole bubbling.

Is there anyway I can help the system to target that particular radiator? ie isolate it and top up that rad with sealer directly or is it a case of just adding a bit more sealer to the system till it stops the leaks?

Thanks for any advice

 

[ree]

Large cast iron rads are usually section rads - just moving them about might have called for splitting the sections:did this happen?

Which joints are you referring to?

 

[meb97me]

Yes they are section rads, the problem radiator in question is pin hole bubbling at a couple of the sectional joins as opposed to the valve joins

 

[muggles]

Isolate rad, add a can of sealer, turn off all other rads and turn the leaking one on, run the boiler for a couple of hours or so heating the leaking rad only, and see if that works. If it does, great. If it doesn't, it's dismantle and re-make the joints time

 

[Nige F]

It was the temperature of the powder coating that did it . I enquired about the process- just out of interest- when I got a couple of rads for my last house. The "expert" who tried to sell it to me @ great expense said it was the only way to go . I nearly told him that my grandfather had been painting them by hand in the 1920's and that had carried on for decades. Just bought a tin of paint - and treated an unpainted one to a shine with blacklead grate polish. I would take your rad off fill with water and a bottle of sealer then pressurise it with a pump to force the mix into the pinholes.

 

[meb97me]

Thanks for the replies, I'd not twigged closing off all the other rads doh!!

Yeah I was a bit apprehensive about the heat of powdercoating with out and testing but thought i'd try my luck as I was really struggling to find anywhere local to refurbish the rad by stripping it down so just plumped with having it blasted and powder coated and crossed my fingers. Hopefully the leak sealer will do the trick if I target this one rad in a particular using the technique muggles detailed.

Thanks again

 

[Nige F]

Definitely trying muggles way first - then mine if you have to But might be best to contact the boiler manufactures to check that sealer is ok- modern boilers are low water content.