I've been raving about Actizyme for a along time now. Great to use regularly on septics & takes care of ponky smells in the bathrooms you don't use very often too.

BUT...if you don't get any joy after a few days with Actizyme, get the water board people out to check your sewer line (there may be roots in the line) and then the plumber to check your end of the sewer line. Apparently you should get your pipes cleaned out every couple of years so in older houses it's often overdue. We've found out the hard day when the sewerage "overflow" (= poo water) came pouring out the inspection point on our back verandah.