What you have is a Cesspool, NOT a septic tank. A cesspool is a sealed underground tank with no outlet. Everything that goes in must be tankered out, which is why you have to empty it so often.
Septic Tanks all have an outlet which discharges into a soakaway. It is illegal to allow the discharge to enter any watercourse or ditch (max. fine £20,000) and it can not be discharged above ground onto land. Neither can final effluent from a sewage treatment unit, as it still contains pathogenic bacteria and viruses
We used to fit the 'in-tank' septic tank conversion units. We stopped fitting them because of too many emergency call-outs for blocked air-lifts, inspection chambers overflowing with raw sewage, etc. They are also VERY expensive. We now suggest that the best way to 'convert' a septic tank or cesspool is to add on a little septic tank conversion unit AFTER the septic tank/cesspool. These cause us no problems and are about half the price.
It is possible to use the final effluent on the garden, but either to an underground system or after UV light sterilisation, which, contrary to most 'experts' advice, need NOT be expensive.
You may like to visit our sewage treatment website as it contains all the information you need on your options, or you can call me on 01757 288022. Our advice and information is free and CORRECT and we will do our best to help you.
Maureen Webb - Waste Tech Environmental Ltd