The effluent from a septic tank is disposed of to a drainage field / soakaway. Under no circumstances should it be allowed to discharge to a ditch, stream or river.  Such a discharge is an offence under the Public Health and Water Resources Acts and renders the offender liable to prosecution by the Statutory Authorities.

In many parts of the UK it is common to find older septic tanks discharging direct to a watercourse.  This is mainly due to septic tanks being installed in areas where the ground conditions do not favour a soakaway system, and as a result the original soakaway has been extended to a nearby watercourse.  No matter how long a septic tank has been discharging to a ditch or any other watercourse, it is still an offence.

Septic tanks can be upgraded into sewage treatment plants by installing a Mantair conversion unit which complies with the requirements of an Environment Agency Permit.