Septic tank backup

A septic tank backup occurs when sewage cannot pass through the tank and out into the drainage field at the expected rate, leading to overflow internally or at external chambers. Common causes include a full tank that has not been emptied, a failed or undersized drainage field that has lost permeability, blocked outlet T-pieces and broken baffles. In Greater London proper, septic tanks are rare, but they are encountered at older properties on the rural edges and across the wider home counties. The General Binding Rules under the Environment Agency require compliant discharge to ground via a proper drainage field. Engineers usually address common causes by arranging emptying, inspecting the outlet and chamber, and recommending replacement with a package treatment plant under BS EN 12566 where the existing system is no longer compliant.