Domestic & Commercial Sewage Treatment Plants

Sewage treatment plants and septic tanks can be a great solution when a mains sewage drainage connection isn’t available. Fully approved to meet environmental standards, each of our products is at an unbeatable price and from a named brand that you can trust. With leaders in the industry like Marsh, Graf, Tricel and Kingspan all offering fantastic sewage treatment solutions you can be sure to find the most suitable system for your needs. Learn how sewage treatment plants work so you can make an informed decision on what's best for you. 

The size of the treatment plant that you will need depends on how many people are using it and you should always overestimate if you’re unsure. For example, if only two people currently occupy a four-bedroom house, it’s safer to install a plant that can handle the sewage of six-eight people as opposed to three-four. Planning ahead with your septic tank or sewage treatment will save costs in the long run. Speak to our Drainage Experts on 01752 692221 if you’re unsure or need any installation advice. Use our guide to see which size sewage treatment plant you need.

Domestic Sewage Treatment

Domestic sewage treatment plants are ideal for any residences that are off-mains. It gives you the ability to collect and treat your own sewage as well as turn it into usable clean water for watering plants or washing cars. Domestic sewage treatment plants are available from Marsh, Graf, Tricel and Kingspan with capacities of up to 50 people and over 15,000 litres. The clean water leftover from a sewage treatment plant can be pumped back into a house to minimise water use and reduce the water bill.

Commercial Sewage Treatment

Marsh Industries and Graf supply commercial sewage treatment plants for over 50 people. Perfect for offices, industrial facilities and campsites that are off-grid, high capacity commercial treatment plants use air compression and minimal maintenance technical components to treat waste water and make it suitable for soakaway or attenuation. Just like in a domestic treatment system you can reuse the clean water from a commercial waste plant.

Septic Tanks

Septic tanks are another method of sewage removal that can benefit remote 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.

Septic Tank Treatments

Here at Drainage Superstore, we offer a range of treatments to increase the efficiency and the lifespan of your septic tank or cesspool. Septic tank treatments we supply include accelerators to increase the speed of waste breakdown and boosting treatments to restore efficiency if your septic tank becomes sluggish. We also have a selection of annual treatments to stop clogging and speed up waste disposal. All of our treatments can ensure your sewage treatment system is operating to the best of its ability and disposing of waste safely.

Sewage Treatment Plant Accessories

Our range of sewage treatment plant accessories will help you to tailor your plant to your needs and ensure you’re getting the most out of your chosen system. We have various different pumps, sampling chambers, manhole covers and risers available to guarantee the perfect fit. Also available are cast iron lids so that your sewage treatment plant is suitable for installation underneath your driveway. The added strength from the cast iron lid will mean that cars and foot traffic can pass over safely without fear of falling or damaging the system.


Wastewater is classed as any water affected by or altered by, human use or consumption. For example, wastewater in the UK includes water from a flushed toilet, from a sink, from a bath or shower and any byproduct of water used domestically, commercially, industrially or agriculturally. In the UK wastewater is collected in waste pipes and sent along the sewer system to wastewater treatment plants. Dependent on the use of the wastewater it can be sent to different areas. Industrial wastewater sewage treatment plants for example deal with industrial wastewater as large industries produce more polluted wastewater. At an industrial plant, it's not uncommon to see wastewater polluted with mercury, chloroform, copper, zinc and varying fats. 

In the UK approximately 5% of households rely on off mains drainage as their homes are too remote to be incorporated into mains sewers. Since these households are so far away from mains sewers and water treatment plants, wastewater is often treated onsite in a sewage treatment plant. The water from this can be safely drained slowly into the ground or a nearby watercourse as it's been treated to the same degree as a domestic wastewater treatment plant. However, by 2020 septic tanks that drain water into a watercourse or a ditch will be outlawed. Wastewater can be extremely polluting so these must be upgraded as part of a push from the Environment Agency. 

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 public sewer, you’ll need either a cesspool, septic tank or sewage treatment plane instead. But what do these three terms mean? Understanding the basic differences between the options available is the first step to getting just what you need.


A cesspool (otherwise known as a cesspit) is essentially a sewage holding tank with no outlet and no facilities to treat the waste that goes in. Waste simply flows into the cesspool to be stored and then, in six to eight weeks when the tank is full, a lorry will tanker it away for disposal. The tank can be vented to allow gas build-up to escape, but 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 soak-away.

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 are multi-chambered and are able to treat and discharge the liquid part of the 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 land, 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. You’ll also need a drainage field or mound that is porous enough to allow the liquid effluent to discharge, something that’s determined by a ground percolation test.

Advantages: Relatively low installation and running costs as they only require emptying (otherwise known as ‘desludging’) 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 the waste relies on natural bacteria, which can be killed off by the bleach or harsh chemicals in today’s wastewater. Septic tank treatments can help keep the bacteria healthy - and your septic tank’s running costs low.

Sewage Treatment Plants

Having your own sewage treatment plant may sound grand, but there are small-scale, affordable domestic units as well as large-scale, commercial units. While several types are available, they all work in the same way (which we’ll explain in more detail below) - by creating an environment that allows the helpful waste-degrading bacteria to flourish.

Most suitable for: Everything from single domestic dwellings right up to large developments. The only option if you want to discharge your treated waste to a ditch or stream.

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

Maintenance: With more moving parts than septic tanks or cesspools, sewage treatment are more prone to wear and tear, so will require regular maintenance.

Septic tanks vs sewage treatment plants: Which one is best?

Sewage treatment plants are fast becoming the preferred option for those not on the main sewage system, but why? The following may help if you’re torn between getting a septic tank and a sewage treatment plant.

Environmental credentials

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, however, produces a clean, non-polluting effluent. In fact, as it leaves the final waste chamber to be discharged, the effluent can be as much as 95% clean, posing no threat to the environment.


No power supply? No problem if you’ve got a septic tank because these don’t require electricity to run. Below is an image of how a septic tank works. Most sewage treatment plants do require a power source because they work by pumping in compressed air or by rotating discs. However, you don’t normally need a very large supply - sometimes just the amount of power it takes to run a 60 watt light bulb. But where will you get this power if you’re off-grid? It normally comes from the main circuit board in your house or a generator. Just be aware that if several households are sharing a sewage treatment plant, you’ll need a shared supply with a separate meter or only one of you will be footing the bill.


Septic tanks have previously been a great option for those not on the main sewer system because they’re incredibly low maintenance - they only need to be emptied once or twice a year and can last for over 20 years. Sewage treatment plants may require a little more upkeep as they have more moving parts, yet they produce such little sludge that they may need emptying even less frequently (although it’s recommended that you do de-sludge once a year to make sure no solids can build up and damage the treatment chamber).


Sewage treatment plants may be more expensive than septic tanks but this is soon recovered in lower running costs.

Legal Compliance

Want to discharge your treated wastewater to a river or stream? By law, a sewage treatment plant is your only option. The UK’s Environment Agency introduced new binding rules on sewage treatment on 1 January 2015 which state, “You must use a small sewage treatment plant to treat the sewage if you’re discharging to a surface water such as a river or stream.” And that’s not all. Even if you already have a septic tank already installed, if it discharges to water you’ll either need to replace it with a sewage treatment plant or discharge to ground instead, by 2020.

What types of sewage treatment plant can you buy?

The main manufacturers of sewage treatment plants include Marsh Industries, GRAF, Kingspan and Tricel.

Market leaders Marsh Industries are best known for their innovative Ensign range, in which all products are unobtrusive, easy-to-install and approved for discharge into a watercourse.

Best known for their high-quality plastic products, GRAF has been making their own sewage treatment plant products for the last few years out of incredibly light but strong plastic. They’re best known for their simple-to-use One2Clean range which produces incredibly little sewage sludge, meaning there are fewer emptying and lower maintenance costs.

Kingspan are known globally for their domestic and commercial Klargester range of sewage treatment plants, but their flagship model has to be the Klargester Biodisc. Its unique design uses a rotating biological contractor - essentially moving discs on which more bacteria can grow and flourish.

Finally, there are sewage treatment plants from Tricel, which are made out of reinforced glass for one of the longest life spans around. Plus you won’t need a concrete backfill with Tricel products, something that 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 01752 692 221 or use the live chat on your screen and we'll be happy to assist you.

Products in Sewage Treatment:

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