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Septic Tank vs. Sewage Treatment System

Sewage treatment systems and septic tanks are an effective solution when a mains sewage drainage connection isn’t suitable. Our tanks are fully approved to meet current environmental standards, at unbeatable price and from a named brand that you can trust. With leaders in the industry like Tricel, Klargester, Harlequin, WPL and Clenviro all offering fantastic sewage treatment solutions you can be sure to find the most suitable system for your needs. 


The size of the treatment system that you will need depends on how many people it will be serving and you should always overestimate if you are not certain. Planning ahead with your septic tank or sewage treatment will save costs in the long run. Speak to our Direct Drainage Experts on 01388 537 050 if you’re not 100% confident in your options or need any installation advice. 


Domestic Sewage Treatment

Domestic sewage treatment systems are perfect for any households that are off-mains drainage. It gives you the ability to collect and treat your own waste as well as turning it into usable clean water for watering plants or washing cars. Domestic sewage treatment systems are available from Klargester, Tricel, WPL, Harlequin, Clenviro and Clearwater with capacities of up to 50 people. The clean water leftover from a sewage treatment plant can even be pumped back into a house to minimise water use and reduce your water bill.


Commercial Sewage Treatment

Klargester commercial sewage treatment plants for over 50 people are perfect for offices, industrial facilities and campsites that are off-mains. Commercial treatment plants use air compression and minimal maintenance technical components to treat waste water and make it suitable for soak away or attenuation. Just like in a domestic treatment system you can reuse the clean water from a commercial waste plant to reduce commercial water bills and meet environmental goals.


Septic Tanks

Septic tanks are another way of removing sewage from households in off-mains locations. They work by filtering the solid matter out of sewage water and separating the sewage sludge and dirty water into two chambers. The water can then be dispersed into the ground via a soakaway system whilst the sewage sludge remains for regular emptying. A Septic Tank can only be installed in areas with suitable space for a soakaway/ drainage field.


Domestic wastewater in remote locations

In the UK approximately 5% of households rely on off mains drainage as their homes are too remote to be incorporated into mains sewers. It is not financially or environmentally viable for these households to connect to a mains sewer, so wastewater is often treated by a smaller sized domestic system. However, many of these systems would have been installed a long time ago and therefore do not meet the current standards of wastewater treatment to discharge legally back into the environment. New laws were introduced in 2020, with the intention of improving the standard of wastewater that is discharged straight into a watercourse. The laws stated that any septic tank that discharges straight into a ditch or watercourse must be upgraded or replaced to meet new standards. Wastewater can be extremely damaging to our ecosystems and is therefore taken very seriously by the Environment Agency who can issue unlimited fines for non-compliance.


What's the difference between a cesspool, septic tank and a sewage treatment plant?

Building regulations state that if you can’t connect to a mains sewer, you need either a cesspool, septic tank or sewage treatment plane instead. But whas the difference? Understanding the fundamental differences between these options is the first step to getting what you need.



A cesspool (or cesspit) is a sewage holding tank with no outlet and no facilities to treat the waste that goes enters. Waste simply flows into the cesspool to be stored and then, in six to eight weeks when the tank is full, a suction tanker will need to take it away for disposal. The tank can be vented to allow gas build-up to escape, whereas a septic tank is otherwise completely sealed.

Most suitable for: Sensitive sites and places that are close to drinking water supplies as all waste will be contained before being safely taken away. A cesspool can be an option if the ground is unsuitable for waste to drainage field.

Advantages: Cesspools are generally the cheapest option, with both a low installation and maintenance cost.

Disadvantages: The sewage inside a cesspool won’t be treated. Cesspools require regular emptying which can cost up to £300 each time, and this may need to be done as many as eight times each year. Not only that but cesspools are banned in Scotland and thought of as a last resort in the rest of the UK.

Maintenance: Using cesspool treatments can help keep the bacteria that break down the waste healthy. This means the solid matter in the tank will remain low, so you won’t need to empty it as frequently.


Septic Tanks

Unlike a cesspool, septic tanks have multiple chambers and are able to treat and discharge the liquid part of sewage. Waste enters the first tank where gravity separates the liquids from the solids. The liquid effluent flows out of the tank and discharges to a network of slit soak away pipes that allows the effluent to seep into the ground, where it is cleaned as it percolates through the soil. The solids sink to the bottom, where some of the ‘sludge’ is broken down by natural bacteria, but the rest will need to be taken away by lorry, as with cesspools.

Most suitable for: A single house or a small development with space for a drainage field or mound that is porous enough to allow the liquid effluent to discharge, this can be determined by a ground percolation test.

Advantages: Low installation and running costs as they only require emptying (otherwise known as ‘desludging’) at most once or twice a year.

Disadvantages: Only suitable if your ground is porous enough to allow the waste to percolate through because septic tanks can no longer be discharged into a watercourse under new laws.

Maintenance: Breaking down waste relies on natural bacteria, which can be destroyed by harsh chemicals such as bleach. Avoid costly clogs by minimizing the amount of chemical cleaners used.


Sewage Treatment Plants

Small scale domestic sewage treatment tanks all work in a similar way. By creating an aerated environment that allows the helpful bacteria that rely on oxygen to digests waste to their maximum capacity.

Most suitable for: Single domestic dwellings to large developments. A sewage treatment system is the only option if you want to discharge your treated waste to a watercourse.

Advantages: Affordable, clean and sewage is treated to a higher standard so that it has minimal negative impact on the natural environment.

Disadvantages: Requires an electricity supply and regular maintenance and, while the volume of solid matter is greatly reduced, it’ll still need pumping into a lorry for disposal at least once per year.

Maintenance: With more moving parts than septic tanks or cesspools, sewage treatment are more prone to wear and tear, so will require regular maintenance. We supply all spare parts for sewage treatment plants here at Direct Drainage.


Septic tank or sewage treatment plant?

Sewage treatment plants are a more futureproof solution to wastewater. Investment in wastewater has grown enormously in recent decades which puts septic tanks at risk of more stringent regulation due to their inferior discharge quality. The sewage treatment plant wins hands down when it comes to being environmentally friendly. Septic tanks make a highly polluting effluent high in ammonia which, under new laws, cannot be discharged into a watercourse. Instead, it can only be discharged to a soakaway or drainage mound for further treatment of the pollutants by the natural aerobic soil bacteria. A sewage treatment plant produces non-polluting effluent as much as 95% clean, posing no threat to the environment.


What types of sewage treatment plant can you buy?

The leading manufacturers of sewage treatment plants include Kingspan Klargester, Tricel, Harlequin, WPL, Clearwater and Clenviro.


Market leaders Kingspan Klargester are known globally for their domestic and commercial flagship model the Klargester BioDisc. Its unique design uses a rotating biological contractor - essentially moving discs on which more bacteria can grow and flourish.


Tricel tanks are made out one of the strongest materials on the market which gives them a really long lifespan. Plus no need for a concrete backfill with Tricel products which can save time and money when it comes to installation.


Our team is trained by manufacturers and suppliers in sewage treatment plants, septic tanks and the relevant accessories. Call us on 01388 537 050 or email and we'll be happy to assist you.