A septic tank can come in all different shapes and sizes. They are the most common type of off mains drainage tank. Some are brick built, some are made of concrete, and more modern ones are made of glass reinforced plastic. Septic tanks are of similar construction to cesspits, with one big difference. The old brick tanks are not sealed. This allows the effluent to seep through the gaps in the brickwork into the surrounding soil. As it passes through the soil, it is converted from ammonia to nitrite, and then anaerobic bacteria converts nitrite to nitrate.

The basics of a septic tank is that it doesn’t have any mechanical parts, and doesn’t perform any `treatment’ of the waste. The waste enters the tank, then separates into three different layers. The middle layer of separated waste water then leaves the tank, typically into a soakaway system. A soakaway system is a network of slotted or perforated pipes, which allow the waste water to percolate through the sub soils without causing a pollution. The solids are then broken down by bacteria until the tank requires emptying.The remaining contents of the tank are then removed at regular intervals by a tank emptying company.

 

A cesspit is a holding tank for the waste from your property. Waste goes in and stays there until the tank is emptied. There is no treatment of the waste that goes in, it simply separates into three layers within the tank. Cesspits are not very common for a couple of reasons – firstly because they pose a greater threat to the environment if they fail, but also because they require a lot of emptying which can become expensive for the home owner.

 

Unless you are buying an extremely old property, the pit will likely be built from brick and sealed to prevent any leakage. Today, some cesspits are made from fibreglass, or brick built with a fibreglass lining. The only piping is an exhaust, to allow the escape of gases which build up in the pit.