if you look after the bacteria in the tank . you shouldn't have to empty a septic tank. font use chemicals to clean toilets , good idea to clean then ( toilets) is to put coke down then leave over night, helps the bacteria grow. also add more bacteria every few months. good tip to give the new packets a good start before you flush em down the loo is to put em in a bucket of water with a few bits of chicken, leave in a dark place for 24hrs then flush