Eric,A septic tank should not have much smell when working properly. The tank will operate normally with bacteria doing all the work. Have you put the wrong household cleaners down the pipework? Sometimes over enthusiastic cleanliness in the house can kill off the bacteria and cause odours from the tank. Check your household cleaners and disinfectants to see if they are suitable for septic tanks. If this is the cause reduce the amount used and the tank will recover after a while. Dont drop the neighbors cat or dog in, it does not work. The bacteria occur naturally.Hope this helps, Mossy: Sir,: I read with interest, on the internet, a problem that I have been having : with odor arising from the vent stacks. You suggested installing a filter : and said that you could provide instructions on hoe to build one or maybe a : reputable manufacturer. Could you please reply back on a filter? My septic : tank and house are only 3 months old and was inspected properly before : closing.: Thanks for your prompt response,: Eric J: Kiowa, Colorado