5 Key Differences Between a Cesspit and a Septic Tank

The most significant difference lies in the way each system handles wastewater.

A cesspit is essentially a sealed underground storage tank. All wastewater from toilets, sinks, showers and appliances flows directly into the chamber where it remains until it is removed by a licensed waste carrier. Because the tank is completely watertight, no liquid is discharged into the surrounding environment.

A septic tank operates very differently. Wastewater enters the tank and separates naturally into three layers. Solids settle at the bottom, oils and grease float to the surface, and partially treated liquid remains in the middle. This liquid then flows into a drainage field where it undergoes further natural treatment within the soil.

In simple terms, a cesspit stores waste, whereas a septic tank begins the treatment process.

For homeowners, this distinction has a substantial impact on ongoing maintenance and running costs.

One of the most common reasons homeowners consider upgrading from a cesspit to a septic tank is the frequency of emptying.

Because a cesspit merely stores waste, it fills relatively quickly. Depending on the size of the tank and the number of occupants, emptying may be required every four to eight weeks. Larger households often require even more frequent visits.

A septic tank, by contrast, separates and partially treats wastewater. Since much of the liquid exits through the drainage field, the tank accumulates waste more slowly. Most domestic septic tanks require emptying only once a year, although usage patterns can affect this schedule.

For many property owners, the difference is striking. A cesspit may require numerous tanker visits each year, while a septic tank often needs just one.

This reduction in maintenance can save significant amounts of money over time and greatly reduce inconvenience.

The financial implications of choosing between a cesspit and a septic tank are often underestimated.

While installation costs vary depending on site conditions, the ongoing expenses associated with a cesspit are usually much higher.

Every time a cesspit reaches capacity, a specialist contractor must attend to remove the contents. Over the course of a year, these repeated visits can accumulate substantial costs.

A septic tank generally proves more economical in the long term. Although it still requires periodic emptying and maintenance, the frequency is far lower. Homeowners therefore benefit from reduced servicing costs and fewer disruptions.

For example, a family living in a rural Dorset property with a cesspit may require several emptying visits annually. A neighbouring property with a properly maintained septic tank may need only a single visit during the same period.

Over many years of ownership, these savings can be considerable.

Environmental responsibility has become an increasingly important consideration for homeowners.

Because a cesspit stores all wastewater, there is no treatment process taking place. While this prevents direct discharge into the environment, any structural failure can potentially result in serious pollution incidents.

Regular inspections are therefore essential to ensure the tank remains watertight and structurally sound.

A septic tank is specifically designed to reduce environmental impact through natural treatment processes. When properly installed and maintained, wastewater undergoes settlement and partial treatment before passing into a drainage field for further filtration.

This process significantly reduces the concentration of pollutants entering the environment.

However, it is important to note that septic tanks must comply with current regulations. In England, septic tank owners must ensure their systems meet the General Binding Rules and do not discharge in ways that could cause pollution.

For many environmentally conscious homeowners, a modern septic tank or sewage treatment plant provides a more sustainable long term solution.