West Wales Waste engineer empting a cesspit

The Differences Between a Septic Tank, Cesspit, and Sewage Treatment Plant

When it comes to sewage disposal, understanding the available options is crucial for selecting the most suitable system for your needs. The most common methods include septic tanks, cesspits, and sewage treatment plants, each with unique features and benefits. This article explores these differences, helping you make an informed decision based on cost, maintenance, capacity, environmental impact, and regulatory compliance.

Septic Tank

A septic tank is an underground tank collecting and treating sewage from households or small communities. It operates by separating solid waste, which settles at the bottom, from liquid waste, which is released into a leach field. The solid waste undergoes anaerobic digestion by bacteria and microorganisms, safely processing the liquid waste for environmental release.

  • Cost-effective: Installation and maintenance costs are lower compared to other systems.
  • Low maintenance: Proper care and regular desludging can ensure decades of service.
  • Environmentally friendly: Natural waste breakdown processes do not require harsh chemicals.
  • Limited capacity: Suitable for a finite amount of waste, challenging for larger households.
  • Regular maintenance: Requires desludging to prevent blockages and backups.
  • Potential for contamination: Improper maintenance can lead to environmental contamination.


Also known as a cesspool, a cesspit is a sealed underground tank for sewage collection and storage. It differs from a septic tank by lacking a drainage field, necessitating regular emptying by professionals.

  • No drainage field required: Ideal for areas with unsuitable soil conditions.
  • Minimal mechanical maintenance: Lacks moving parts, reducing the need for upkeep.
  • Large capacity: Can accommodate more waste, suitable for bigger households or communities.
  • Higher installation cost: More expensive to install than septic tanks.
  • Frequent emptying: Professional emptying services are required, adding to the cost.
  • Potential for odours: Can emit strong odours, particularly in warmer weather.

Sewage Treatment Plant

A sewage treatment plant is an advanced system that treats sewage through mechanical and biological processes. It effectively breaks down waste using microorganisms, then filters and purifies the water before environmental release, also addressing nutrients and other pollutants.

  • Efficient treatment: Produces clean, safe water suitable for larger communities.
  • Environmentally friendly: The purified water is safe for release without harming the environment.
  • Versatile: Capable of handling significant amounts of waste.
  • High cost: The most expensive sewage disposal option.
  • Regular maintenance: Requires ongoing monitoring and maintenance for proper function.
  • Electricity dependent: Its operation relies on a consistent power supply, posing challenges in areas with frequent power outages.


Choosing the right sewage disposal system—be it a septic tank, cesspit, or sewage treatment plant—depends on several factors, including cost, maintenance requirements, waste capacity, environmental considerations, and local regulations. While septic tanks offer a cost-effective and environmentally friendly solution for smaller setups, cesspits may be preferred in areas with poor soil conditions despite their need for regular emptying. Sewage treatment plants, although more costly, provide efficient waste treatment for larger communities. It’s advisable to consult with environmental and sewage management professionals to determine the most appropriate system for your specific situation, ensuring compliance with environmental standards and long-term sustainability.