The WPL Diamond Sewage Treatment Range

Market-leading environmental wastewater solutions

Specially designed for homes that have no access to wastewater mains drainage, the WPL Diamond sewage treatment range is fully compliant with all UK building regulations. Each plant is purposely sized and offers the highest-quality discreet wastewater treatment. With low ongoing running costs and great value for money, the unique design gives clients complete peace of mind. Installed in more than 40,000 homes worldwide, it is a proven high-quality sewage solution.


Benefits of the WPL Diamond sewage treatment range:





  • Simple design and no moving parts makes for reliable operation
  • Low running costs equivalent to a small, quiet air blower
  • Great value for money
  • No odours
  • High performance which meets Environment Agency consent standards
  • Very little visual impact – there’s just a small lid which sits flush to the ground
  • Easy to install with minimal labour and materials – no need for large plant excavation or handling
  • De-sludging intervals of up to 3 years, thanks to continuous bacterial digestion
  • Reduced need for concrete backfill, thanks to its robust construction
  • Compact design
  • Reduced soakaway
  • CE marked and Irish Agrément certified.




The Diamond DMS range comes with a comprehensive 5-year parts and workmanship warranty on the blower and plant. The Diamond DMC range comes with a comprehensive 2-year parts and workmanship warranty on the blower and plant. The unit’s sturdy GRP construction and WPL’s quality assurance procedures permit a minimum life expectancy of 25 years.



Servicing and maintenance

Each unit comes complete with a comprehensive service and maintenance manual. You will find that fewer than 2 hours of maintenance are required each year. You can choose to purchase a service and maintenance agreement from WPL or from us. De-sludging takes place around every 3 years, thanks to the continuous bacterial digestion.

More about the features of the WPL Diamond sewage treatment range:

Optional External Pump Chamber (EPC)
If the Diamond plant is located on an incline, in a high water table area or a long distance away from the designated discharge point (eg soakaway/water course/ditch), the final effluent may require pumping. The Diamond DMS range can be specified with an EPC which can deliver up to 100 litres per minute of effluent at a head of 4m. The EPC can be simply retro-fitted and is easy to maintain.

The external pump chamber consists of:

  • 240v, 0.25kw submersible pump, integral float switch with stainless steel internals
  • High level alarm beacon
  • Junction box
  • 32mm MDPE pipe outlet
  • Invert extension kit for the EPC also available (optional extra)


How it’s installed
Stepped excavation minimises the amount of backfill material required and the Diamond’s lightweight design means it can be moved easily around the site.


How the process works
The central aeration chamber (1) is a circular tank with a sloped open base, which empties into the bottom of the outer clarifier chamber (2).


Located in the centre of the aeration chamber is a 200mm diameter draft tube (3), which extends to 100mm from the bottom of the clarifier. Air is released at the bottom of the draft tube through a disc plate diffuser (4).


As the diffused air rises in the draft tube it causes an upward flow of process fluid. This draws the settled solids (5) from the bottom of the clarifier up through the draft tube where they are discharged at the surface of the aeration chamber.

The design of the draft tube ensures continuous and complete mixing of oxygen with the sewage. This oxygenation allows the various aerobic organisms that biologically degrade the wastewater contaminants to grow. Gravity causes the aerated solids to settle at the bottom of the tank where they are again drawn back up through the draft tube.

As raw sewage enters the aeration chamber, it displaces biological solids from the aeration compartment to the clarifier. Less turbulent conditions in the clarifier allow the digested solids to settle to the base where they are returned back to the aeration compartment.

The clarified (treated) effluent flows slowly up through the clarifier and over a weir (6), which extends around the periphery of the tank.


The effluent collects in an outer trough where it is discharged through a 110mm pipe connection. The scum baffle (7) located inside the overflow weir prevents floating solids (8) from passing over the weir.


How the process works
The Diamond is designed to “clean” the wastewater to a standard of 20mg/l Biological Oxygen Demand (BOD) and 30mg/l Suspended Solids (SS) 20mg Ammoniacal Nitrogen (AMM-N) on a 95 percentile basis. Additional filtration equipment is available to extend the treatment process to meet standards as high as 10mg/l BOD and 15 mg/l SS. If more stringent environmental requirements are specified, please contact Drainability for details.


Blower installation
Each blower is supplied complete with an alarm and an enclosure to protect it from outdoor conditions. It should be connected to a single-phase supply (240v) via a suitable IP55 rated weatherproof socket or fused spur (not supplied) by a competent electrician. Included is 10m of airline to connect between the blower and the tank, however, blower installations of up to 30m from the tank can be accommodated. Please contact WPL or your authorised distributor for advice


WPL manufactures the full range, and units are delivered ex-stock.


WPL is a world-leading designer and manufacturer of high-quality package and turnkey sewage treatment systems, rainwater harvesting and grease management solutions.


With over 16 years’ industry experience, WPL services an extensive customer portfolio comprising the UK’s major water utilities, all areas of the commercial sector and the domestic market place. The company’s consistent focus on ecology, coupled with extensive research & development into new technology, have enabled it to far exceed all existing and proposed discharge consent standards enforced by the Environment Agency, SEPA and other regulatory authorities.