At Wessex Drainage, we provide professional installation and maintenance of septic tanks, cess pits and packaged sewage treatment plants across Wiltshire and Hampshire including Salisbury, Winchester and Southampton. With increasing regulations from the Environment Agency, it is important to choose the right off-mains drainage solution for your property.
Septic Tank Installation and Emptying
We install septic tanks in suitable locations, although permits to discharge are now harder to obtain. In many cases, a packaged sewage treatment plant may be a more environmentally friendly and compliant alternative.
Septic tanks must be emptied or de-sludged at least once a year. If your system requires more frequent emptying, this may indicate a problem with the soakaway, often caused by a broken T-pipe. In most cases, our team can clear the issue using high pressure water jetting.
Cess Pits
A cess pit is a sealed tank that provides temporary sewage storage and must be emptied regularly, sometimes as often as weekly. This makes cess pits expensive to maintain. They are usually only used where regulations prevent septic tank installation, such as near rivers or environmentally sensitive areas. In many situations, we can overcome restrictions by installing a sewage treatment plant instead.
Sewage Treatment Plants
Packaged sewage treatment plants are now the most popular choice for off-mains drainage. They are affordable, efficient and far more acceptable in today’s green climate.
The process is similar to a septic tank but includes mechanical components that aerate and treat the waste, producing an effluent that is up to 95% clean and ready for discharge (subject to Environment Agency consent). Systems range from small units suitable for homes to large plants for hotels or commercial sites.
Modern sewage treatment plants can even adjust to different usage levels, self-test, diagnose faults and ensure the highest quality discharge.
Whatever your requirements, Wessex Drainage can supply, install and maintain the right off-mains drainage solution for your property.

