My Mum has a septic system and I know she buys a special enzyme cleaner. No idea what it's called but I can ask her. I was actually really impressed with it and had swapped to a similar product for a while instead of bleach until our local supermarket stopped stocking it. :grrrr: She gets hers mail order from somewhere in Perth. I gets rid of smells completely (even dog urine) and is safe to use all over the place.