Cesspit vs Septic Tank: How Do I Know Which One I Have?

If you live in a rural or off-grid property in the UK, you likely rely on a private waste system—either a cesspit or a septic tank. But which one do you have, and how do you tell the difference? In this blog, we’ll break down exactly how each system works, how to identify them, and what the pros and cons are.

What is a Cesspit?

A cesspit (also known as a cesspool) is an underground storage tank that holds sewage and wastewater without treating it. These are usually found in older or remote properties and must be emptied regularly by a licensed waste contractor.

Modern cesspits are typically made from fibreglass and are completely sealed to prevent leakage. They have a single pipe for ventilation and one large chamber that stores waste.

How Does a Cesspit Work?

• Wastewater from your home flows directly into the tank.
• The tank stores all the waste without separating or treating it.
• When full, it needs to be emptied using a vacuum suction tanker.

Key Facts:

• No waste treatment involved.
• Requires regular emptying—monthly, quarterly, or seasonally.
• You must have planning permission and meet Building Regulations.
• After each emptying, you should receive an official waste transfer note.

Pros of Cesspits:

• Simple to install.
• Ideal for small or temporary properties.
• No need for drainage fields.
• Low mechanical failure risk.

Cons of Cesspits:

• High maintenance due to frequent emptying.
• Long-term running costs can be high.
• Illegal in some areas unless specific regulations are followed.

What is a Septic Tank?

A septic tank is a self-contained wastewater treatment system. It not only collects but also partially treats wastewater on-site using natural biological processes before discharging it safely into the ground through a drainage field.

These are common in rural UK areas without access to mains sewerage.

How Does a Septic Tank Work?

• All household wastewater enters the tank.
• Solids settle at the bottom (sludge), while oils float to the top (scum).
• Bacteria in the tank break down waste.
• Treated water flows into a drainage field where it is further filtered by soil.

Pros of Septic Tanks:

• Environmentally friendly treatment system.
• Less frequent emptying than cesspits (typically every 1-3 years).
• Long lifespan (up to 40 years with good care).
• No need to connect to the mains sewer.

Cons of Septic Tanks:

• Initial installation cost is high.
• Requires soil testing and planning approval.
• Not suitable for all property types or soil conditions.
• Repairs can be expensive if the system fails.

How to Tell if You Have a Cesspit or Septic Tank

Here’s how to quickly identify which system you have on your property:

Septic Tank

• Has 2 to 4 visible manhole covers.
• May have a vent pipe sticking out of the ground.
• Only needs to be emptied every 1-3 years.
• Discharges water into a nearby drainage field.

Cesspit

• Has only one large manhole or access cover.
• Fills up quickly and needs frequent emptying.
• No outflow pipe or drainage field.
• Fully sealed with no internal chambers.