Septic Tanks vs. Cesspits: What Is the Difference?

Numerous properties in Suffolk are located in rural areas with no access to the local mains sewerage system. The only option for many homeowners and businesses based in the countryside is to install an ‘off-mains’ sewerage solution, ensuring wastewater can be safely disposed from their property.

Septic tanks and cesspits are two of the most common off-mains sewage systems. But what is the difference between the two, and how do you know which is the best solution for your home or business?

Septic Tanks

A septic tank is an underground tank that separates solids and liquids into separate chambers, allowing for the safe passage of wastewater into the surrounding environment.

Septic tanks operate in a relatively simple way: wastewater enters the first chamber where solids are allowed to settle and decompose. Liquids pass through into the second (or possibly third) chamber, before being released into a soakaway or drainage field, which lets the filtered water disperse directly into the ground.

The solid material is removed separately using a vacuum pump, a procedure that usually needs to be performed at least once a year by a registered waste handler.

As of 1 January 2020, it is illegal for any septic tank to discharge water directly into a local watercourse, whether that’s a stream, river or lake. The new regulations, known as the ‘General binding rules’, were implemented to limit the pollution of UK watercourses.

Most water released from septic tanks contains pollutants that can harm the environment. Homeowners and businesses must therefore upgrade their tank to a sewage treatment plant, which will purify water before disposal, or alternatively install a soakaway or drainage field. Anyone found in breach of the regulations could face prosecution or a substantial fine.

Because they don’t need emptying regularly, septic tanks are recommended for anyone looking to dispose of their waste in a cost-efficient manner.


Like a septic tank, a cesspit is a large tank installed underground to collect sewage and wastewater from commercial and domestic properties.

However, while a septic tank treats wastewater before releasing it safely into the ground or surrounding waterways, a cesspit simply collects and holds sewage until it is ready to be removed. All sides of the cesspit are sealed to ensure the waste is contained within it, and a manhole cover typically provides access for waste collection.

Cesspits should be emptied regularly by a registered waste handler – this could either be monthly, quarterly or yearly depending on property size and water usage, but most cesspits tend to need emptying every 45 days. Once emptied, the waste is taken to a specialised facility for safe disposal.

A cesspit is ultimately a more expensive off mains solution than a septic tank, owing to the cost of emptying it regularly. However, it is still a perfectly viable and environmentally friendly option if water cannot be discharged through the ground.

The off-mains drainage experts

At Drain Doctor, our technicians are fully trained in the installation and maintenance of septic tanks and cesspits. As a registered waste handler, we can also assist with the ad-hoc emptying of cesspits, as well as the upgrade of septic tank systems in line with the new regulations. Get in touch today to learn more about our services, or to book a visit from one of our technicians.