I don't know if this will help, but many years ago I had a similar problem with a hoover machine. This machine had a small plastic type bottle connected to the drum by a small clear plastic pipe. Living in a hard water area this had become all furred up which stopped the pressure build up in the hose and bottle, this pressure controls the amount of fill in drum, no pressure and it just keeps on filling. I replaced the bottle and cleaned the tube and led a normal life after. Hope this helps.
David, May 2006