One of your traps could be siphoning or there might be a broken pipe in wall, The way you sound it could be comming from the vent on the roof when wind blows a certain way, if so then the one thing you can do is put a house trap in your outside sewer line, some time if you extend vent on roof that helps, try that first, let me know.
Art retired plbg
» This message has been edited by John Aldrich on 01 November 2004