could be the neighbours blocking the drain. I have had this before where it turned out to be my neighbour flushing chippan fat down the drain, and this blocked the drains for the whole street.
Gary, June 2005
have you tried lifting the manhole covers outside to see if your drains are blocked?????
steve, May 2005
edit
I can answer this question...
My toilet gets stopped up several times a week. Why?
