macdee pneu cistern 6 litre concealed cistern that keeps running?

I have one of these cisterns, and it is a recurrent problem, and I still don't know what the cause is! I have found that taking off the filling valve assembly, dismantling it, and putting it back together usually puts it right. But check carefully as you dismantle, so you can put the parts back in the right order!

Alan Lunt
February 2010