Reading up on some of the links provided in this thread, I think that would indicate a badly maintained system/too much pressure. And I'm now quite sure I had

Reading up on some of the links provided in this thread, I think that would indicate a badly maintained system/too much pressure. And I'm now quite sure I had to deal with a single-pipe system modified to not have individual valves. Quite insane, but I guess that's what cheap owners will do.