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My husband and I recently bought a home that uses a gas fired Weil McLain cast iron steam boiler with intermittent ignition. I was told that it should be partially drained every so often to remove the "brown" clogging sediment. Does anyone know how to do this? We don't know which valve to turn.
Additionally, whenever the boiler starts up it makes a banging noise. Is this a problem? The noise also seems to have become louder after I mistakenly filled the test tube apparatus (indicating the water level) a little too much. Is there cause for concern? Does anyone have any suggestions on what to do AND how???
35 YEAR MASTER PLUMBER, HEATING, ELECTRIC, DRAINS, FIRE SPRINKLERS, WATER HEATER AND BOILERS SINCE JAN, 1989
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Intermittent ignition is unrelated to any sludge or overfill and IS a real problem. If the banging noise is gas-explosions due to faulty ignition it's in fact a serious hazard. Have a pro deal with ignition issues.
If the banging noise is condensed water flowing back from the radiators and "exploding" when it drips into a vertical pipe filled with superheated steam it's annoying, but not necessarily a problem, but it may be reduced by lowering system pressure and adjusting the air valves if somebody has been monkeying with it.
Overfilling the boiler isn't likely to affect that issue one way or the other though, but draining it down to a proper level (about midway on the sight gauge) is still important. There's usually a triangle-shaped casting with a valve handle on it near the sight gauge for blowing sludge and draining down. See: http://www.youtube.com/watch?v=iDxofrGeeEw
If the boiler is in decent shape it's probably worth hiring somebody to re-commission the system and show you how to adjust the air valves, drain down the sludge, etc. Many systems have been over-tweaked to higher than necessary steam pressures, which can aggravate radiator bang issues. People seem to do that when the air-valve on some radiator isn't venting right and they think it needs more pressure or something. (1/2-1 psi is plenty for a residential system.) If you want to learn to adjust and maintain it yourself, buy this book. Set up properly they're quieter, more efficient and more comfortable.
There are plenty of youtube steam boiler maintenance vidis that may be a useful way to familiarize yourself with the system. (I haven't screened more than a couple of them- do your own searches, but there's plenty of DIY video out there that works better than 10,000 words and paper diagram.)