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???