This is a general guide on these drainage features, with the aim of helping you understand the functioning and purpose of these aspects of your property.
There have been significant changes in recent years and you may need to update your sewage system and/or apply for a permit, depending on your circumstances.
Check out these changes by clicking below.
These are all things that end up discharging water into the ground.
Let’s start with what these are, so we can identify and understand how they work and what’s needed to make them comply with modern regulations.
Cesspit (or Septic Tank)
A cesspit, or septic tank, is a large underground container used for the storage and partial treatment of sewage and wastewater. Unlike a mains sewer connection, a cesspit collects waste on-site and requires regular emptying by a specialist service. Septic tanks, on the other hand, allow for a basic treatment process where solids settle at the bottom and liquids drain into a soakaway or drainage field. These systems are typically used in rural areas where mains drainage is not available.
The majority of septic tanks in the UK tend to be private, serving only individual properties – but can be shared where a single property has been split into multiple properties or a single landowner had several houses on one plot which has since been split.
If you’re not sure, it could be worth checking the deeds or any plans if available…
Treatment Plants
Treatment plants are advanced systems designed to process and treat sewage and wastewater more thoroughly than septic tanks. These plants use mechanical and biological processes to break down contaminants, resulting in cleaner effluent that can be safely discharged into watercourses or soakaways.
Domestic treatment plants are ideal for homes and small communities not connected to the main sewer system, providing an environmentally friendly solution for wastewater management.
Although on the face of it more expensive to install and run, treatment plants are far more effective (and quicker) at treating waste and should require fewer visits from a tanker to empty.
But they still require certain maintenance like anything else of this nature!
Here’s some boiler plate for you, in case it’s useful. You can see that Building Regulations Part H plays a huge part in designing drainage, so if you find yourself unsure of exactly you need to comply, here’s a free PDF courtesy of Gov.UK:
Otherwise, here’s a breakdown of what to bear in mind when dealing with these aspects of drainage…
Septic Tank Regs
Cesspit Regs
Treatment Plant Regs
How Cesspits Work
Collection of Wastewater
All household wastewater, including sewage, is piped directly into the cesspit, a sealed underground tank.
Storage
The cesspit stores the wastewater. Unlike septic tanks, cesspits do not allow for any treatment or separation of solids and liquids; all waste is contained within the tank.
Emptying
The cesspit must be emptied regularly by a licensed waste carrier, as it has no outlet for liquid effluent. This prevents overflow and potential contamination of the surrounding area.
How Septic Tanks Work
Collection of Wastewater
All household wastewater, including sewage, is piped directly into the cesspit, a sealed underground tank.
Separation of Solids and Liquids
In the septic tank, solids settle to the bottom, forming sludge, while lighter materials like fats and oils float to the top, forming a scum layer. The middle layer contains partially clarified liquid.
Anaerobic Digestion
Bacteria in the tank break down the solid waste anaerobically, reducing the volume of sludge and partially treating the wastewater.
Effluent Discharge
The partially treated liquid effluent flows out of the tank into a drainage field or soakaway, where further natural filtration occurs as it percolates through the soil.
How often should Cesspits and Septic Tanks be Emptied?
Cesspits
Cesspits should be emptied more frequently than septic tanks due to their design, as they do not treat or discharge any wastewater.
Regular Emptying
Typically, cesspits need to be emptied anywhere from 6 weeks up to 12 months, depending on the size of the tank and the volume of wastewater produced by the household. Larger households or higher water usage may necessitate more frequent emptying.
Monitoring Levels
Many modern cesspits have an alarm system that alerts the homeowner when the tank is nearing full capacity, ensuring timely emptying and preventing overflow.
If you your tank has no alarm and you lose track of when it was last emptied, your nose may be the next best thing. Smells and slow-running sinks and toilets may indicate the tank needs emptying.
Professional Service
Emptying should be performed by a licensed waste carrier who will safely remove and dispose of the waste according to local regulations.
Any local or national tanker company should be able to empty your tank with relative ease, and because there are so many drainage companies across the UK, you should be able to find a fairly competitive price.
Septic Tanks
Frequency of Emptying
Septic tanks require less frequent emptying compared to cesspits, as they treat and discharge the liquid portion of the wastewater.
As in, these are not a closed system but some of the water, once the waste aspect has been “treated” by bacteria breaking it down, leaves the tank and enters a water course or into the ground further away from the property.
On average, septic tanks should be emptied every 3 to 5 years. This does depend on various factors such as tank size, household size, and the amount of solid waste generated.
Monitoring Sludge Levels
This can help prolong the life of the drainage field the tank discharges into, in the same way that maintaining your surface drainage can prolong the life of a Soakaway. It helps keep the solids from forming and clogging the outgoing pipe system.
Generally, once the sludge or scum forming is around 1/3 of the top layer, it’s time to empty.
Equally, however, you do not want to empty the tank too often as this can cause less efficient breakdown by removing too much of the good bacteria.
Professional Inspection
Regular inspections by a professional can help determine not only the appropriate emptying schedule, but the condition of the tank itself.
This can include signs of the tank structure, making sure it’s still watertight and not polluting the surrounding ground and checking the inspection cover is safe and sound.
How Treatment Plants Work
Collection of Wastewater
Wastewater from the property enters the treatment plant in the same manner as Cesspits and Septic Tanks.
Primary Treatment
In the primary treatment chamber, solids settle to the bottom, and some anaerobic digestion takes place, similar to a septic tank.
Aeration (Secondary Treatment)
The liquid effluent then moves to an aeration chamber, where air is introduced to promote aerobic digestion. Aerobic bacteria break down organic matter more efficiently, significantly reducing pollutants in the wastewater.
Secondary Settlement
The treated water then enters a secondary settlement chamber, where remaining solids settle out, resulting in clearer effluent.
Discharge
The treated effluent is discharged from the plant, usually into a drainage field, soakaway, or directly into a watercourse, depending on local regulations and environmental permits. The discharged water is much cleaner and safer for the environment compared to untreated or partially treated wastewater.
Knowing how these features of your drainage or your customer’s drainage should help you work out how to look after them and identify any issues.
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