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Harlequin CAP18 (up to 18 Person)

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 The Harlequin CAP18, compact sewage treatment plant, is specifically designed to treat domestic sewage in a simple and compact system making sure it is safe to be discharged into a watercourse such as a river or stream. It is suitable for domestic installations of up to 18 people. With a life expectancy of over 20 years, you can enjoy absolute peace of mind.

Manufactured from durable Medium Density Polyethylene (MDPE) material, the CAP18 is one of the most stable and easy to install sewage treatment plants. It’s unique bio media system delivers a pollutant removal level of 96.2% whilst also combatting common problems associated with small packaged domestic plants. Contemporary design engineering and analysis software and state-of-the-art manufacturing facilities combine to create this unique product which dominates the domestic sewage treatment plant market. Market-leading performance, easy installation, super quiet operation, low maintenance costs, reliable bio media system and durability are all qualities that make the product best suited for a wide range of off-mains sewage treatment requirements.

CAP18 comes in both gravity and pumped outlet versions. Its equipped with an external blower for optimal performance. The blower is conveniently located in a weatherproof aboveground external housing. This compact system comes with a 2-year warranty (only when product is registered on our website) and is certified for use in the UK in compliance with EN12566-3.

 Please call us if you are need additional risers on 01388 537 050.

Population Served 15-18
Desludging Interval 12 months (depending on usage)
Inlet Invert 600mm
Outlet Invert 750mm
Blower Rating 105W
Length 3615mm
Width 1620mm
Height 2140mm
Weight 600kg
Manhole Cover Size 600mm x 450mm


  • Tank body moulded in one piece from durable Medium Density Polyethylene Material (MDPE)
  • 110mm inlet and outlet connections
  • 110mm services duct
  • Integrated lifting eyes for ease of handling and installation
  • Fully secured 600x450mm pedestrian duty flush fitting manhole cover to comply with statutory regulations
  • Above ground air blower housing delivers more reliable and efficient operation; allows easy access for maintenance
  • Moving Bed Biofilm Reactor (MBBR) system ensures there is no fixed media, eliminating blockages
  • Easy access to the bubble diffuser within the tank
  • Compact size and lightweight ensures lower installation costs
  • Super quiet when installed correctly
  • 12-month service period reduces operating costs
  • Mechanically reliable with no moving parts or electrics within the tank
  • Certified for use in UK in compliance with EN12566-3
Super Quiet – With a high performance Linear diaphragm blower housed in a weatherproof aboveground external housing, the operation of the plant is super quiet.

Low Maintenance Costs – There are no mechanical moving parts or electrical components within the plant allowing for extremely safe and easy maintenance. At full occupancy the systems need to be emptied only once every 12 months which effectively means you spend less on maintenance of the plant.
Odourless – The plant is hermetically sealed eliminating any odour emanating from within the tank.

Market leading performance – Producing an excellent 96.2% pollutant removal level, the final effluent can be directly discharged into a stream or soakaway.
Reliable Bio Media System - The plant operates with a unique bio media system meaning there is no fixed media eliminating blockages that are commonly found in smaller treatment plants.

Durable & Stable Product - Made from MDPE, this is one of the most durable and stable sewage treatment plants you will find in the market. The wide base gives it the added stability. Once installed, you can enjoy complete peace of mind.

Harlequin CAP18 Installation Guide 

Harlequin CAP 18 Product Drawing

Harlequin CAP 18 Specification Sheet

  Commissioning and Servicing Information

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