Clarke Contractors are accredited installers and service providers for

Graf Wastewater Treatment Systems.

Are you having problems with your septic tank or sewage treatment system? You could be covered by your home insurance for a brand-new system.
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Our wastewater treatment product range spans everything:
Cesspools, septic tanks, pumped manholes, full sewage treatment plants, drainage fields, soakaways, Percolation Testing.

Our services, as with all our other systems, also spans everything from design through to installation, commissioning, and maintenance/servicing. We can manage Building Control, Welsh Water and Natural Resource Wales on your behalf. For us to propose the correct wastewater treatment system and service for your site, please send us as much information as you can about the use of the building, the number of people within the building, any consent to discharge documentation from the environment agency and any drainage layouts that you may have. We can then ensure that our proposal meets all relevant standards and planning criteria.

What is wastewater treatment?

The definition of sewage (waste water) is both grey water which is water used in private houses from toilets, dishwashers, sinks, baths and showers and black water which is any water from toilets. This foul water can be treated by using either biological matter to break down the waste or physical treatment using aeration to treat the water.
Wastewater treatment, also known as sewage treatment, is the process of removing contaminants and suspended solids from primarily household waste such as toilets, showers and sinks but also from commercial properties such as office spaces and factories and producing treated water to go back into a watercourse such as a stream or river. The treated water is not however clean enough to drink but is safe enough, so it will not harm the environment. 

If the water is not treated and discharged correctly this can cause pollution and diseases. In the past sanitary conditions were not very good at all which is why we now have regulations on how sewage should be dealt with.
If you are not connected to the main sewer network, then you will need to install some form of sewage treatment system to process the wastewater into a form that can be safely drained into your local watercourse or can be discharged into a soakaway.

There are three levels of wastewater treatment; primary, secondary and tertiary. Primary treatment is when the wastewater is temporarily held in the tank. The solids will settle at the bottom of the tank and the remaining water will discharge into a soakaway which is known as a septic tank. Secondary treatment is when the wastewater is treated using either oxygen or media which encourages the growth of bacteria to break down the solids. This is carried out in cycles. Tertiary treatment is used when additional treatment to the water is needed on top of the secondary treatment, for example, the Graf Klaro +P package will remove phosphate found in the water.

There are a few options for a wastewater treatment system.

Advanced WWT System

The advanced WWT systems work in a very similar way to the one2clean system, using SBR technology, however, they provide additional modules for further treatment of the water and much more.


The one2clean system is a sewage treatment plant that will treat the water, so it is clean enough to be discharged into a watercourse. Whether the water can be used for irrigation depends on the local Water Authorities. The water discharged from the packaged treatment plant must meet the relevant British Standard which is BS EN 12566 for small sewage treatment plants and BS 6297:2007 for drainage fields. This does require a power source and will require emptying approximately every year. How often a system requires emptying depends on how frequently it is being used and the manufacturer’s guidelines. The sludge which builds up at the bottom of the tank must also be emptied in line with the manufacturer’s instructions.

Cesspool & Septic Tanks

A cesspool is a holding tank for wastewater that does not have an outlet. No treatment is carried out and it will need emptying a minimum of every thirty days (monthly). If it needs emptying more regularly than this then it is the wrong size for the property. A larger tank volume is required for a cesspool compared to a treatment plant. A septic tank includes a baffle to keep the solids in the inlet side of the tank. This uses a natural bacterial breakdown to separate the sludge and liquid. The liquid then passes over the baffle and is discharged via the outlet to a soakaway where the liquid effluent is dispersed into the soil and the waste is broken down. A septic tank needs emptying approximately every six months.

Large Commercial Advanced WWT system

The Large Advanced WWT systems are for more than 50 inhabitants and also use SBR technology. Click here for further information.

Why Choose Clarke Contractors?

Experienced company with true tradesmen - Free no-obligation quotes - Family run business - We take pride in our work - Fully licensed - Affordable prices - Qualified team - trained & accredited by Graf UK

Trusted across North Wales and The North West

We're a North Wales based company servicing the region with a wealth of experience in the trade, we have built a reputation for providing high standards of workmanship and customer care.

CQMS Safety Scheme Accreditied

We're proudly accredited by the CQMS Safety Scheme. Our team has demonstrated the required level of competence and compliance with the SSIP Core Criteria and is certificated by CQMS' Safety Scheme.

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