Jeremy
I think Christian, in his posting, gets to the source of your problem. Your
original kit may have had a, probably brass, filler tube going below the
surface, so you would not have heard much filling noise. You can't get them
any more as they break the water bylaws because of syphoning. The new way,
as Christian mentions, is for a long flacid plastic thing to replace the
open brass filler pipe.
Paul