You may think the smell indicates that the tank is full and needs emptying. This could very well be the case if you are a household of between 4-6 people and it’s been 12 months since your tank was last emptied, however there could be a number of other reasons why you are experiencing this issue which would be worth investigating before you conclude the former: 1. The drain field may have failed or tanks may be leaking sewage (in which case you would need a repair specialist) 2. One of the manholes may not be completely covered or a concrete lid may be broken, or, if a plastic lid, the seal on the lid may be leaking 3. The aeration tank may not be receiving the appropriate amount of air, which can be caused by a stopped-up air system, broken air lines, clogged air filter or improperly operating air compressor or aerator 4. Overuse of water, such as washing a lot of laundry in one day 5. Septic odours are being trapped near the ground by high air pressure, especially on a very hot, windless day, or 7. One of your neighbours has a septic problem and the septic odour is coming from their tank/drain field In any case, it’s always advisable to obtain quotes from professional companies should you feel there’s a problem. If you are unsure how to begin, just put ‘septic tank emptiers’ plus your town into the search engine to get a list of local companies to you, then ask for a couple of quotes to get the best price.