Localised sludge in C/H circuit

coffeehound

One radiator needed to be bled regularly so someone :whistle: thought it would be a good idea to fit an automatic bleed valve.

Fast forward some years and two radiators downstream are now sludged up. If we were to remove and flush those two/three rads, is that likely to be good enough, or should the whole system also be flushed do you think?

As for the air leak, is it likely to be a valve seal? Would it be a case of pinching up the packing nut on the problem rad's valves and those upstream? Thanks

Alex1983

The air could well be hydrogen not air, a by product of sludge.

It could also be a design issue, the pump being in the incorrect place in relation to the cold feed and open vent putting parts of the system under negative pressure and suck air into the system.

nofoollikeold

1. Fitting automatic bleed valves only masks the problem. Fresh water is being added, complete with its oxygen, when the valves operate.
2. Why not try removing and flushing the two sludged up radiators and see if it makes the problem disappear? If that doesn't work, get the system power flushed.
3. You need to find the problem and fix it for any solution to work. Consider the points Alex1983 has made. Beyond that you'll have to check every joint in the system (prioritising compression and push fit joints, soldered joints rarely leak). Try tying a "bow" of tissue / kitchen roll under each radiator valve. Small leaks often don't show up, but may be enough to soften the paper and make it droop.

coffeehound

Thanks for the useful info and advice, gents, will check/do those items in turn