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This is a new boiler on a really simple one-pipe system. When I first arrived the system was flooded despite the customer having drained it down earlier that day. I drained it then fired it up. Within a few minutes it went off on low water then filled, going through this process 2 more times within a half hour. Holding up condensate! I double-checked to make sure the feeder wasn't creeping (it wasn't). I skimmed it then cleaned it with Dry Steam, flushing out lots of goo. Found the pigtail plugged: cleaned it out. As I was about to leave I checked the sight glass--it was right down to the bottom, but the boiler hadn't filled yet. Well, it took over a week but the dang thing flooded again all right. When I drained it there was still a bunch of crud. I will probably try cleaning again, but I would greatly appreciate any suggestions.