Septic Tanks

Our range of modern and efficient septic tanks

Septic Tanks

Traditionally, most homeowners used a septic tank in order to treat domestic wastewater. It was the most popular and economical solution available, especially in areas where mains drainage was not available. Many septic tanks are non-compliant and don’t adhere to the General Binding Rules set out by the Environment Agency. A percolation test must be conducted in accordance with the guidelines and the septic tank replaced with a suitable sewage treatment plant. Septic tanks are designed to provide only basic treatment of wastewater, which is not ideal for this type of sewage waste management process. While they are a cost-effective solution, their performance heavily depends on an adequately designed soakaway system. Furthermore, they are not equipped to handle changes to the water table, which can significantly affect their efficiency. Consequently, septic tanks often perform poorly and cause substantial mental and financial stress to homeowners, in addition to polluting nearby watercourses.

Septic Tank Treated Wastewater cannot  be discharged into a watercourse.


The Environment Agency has therefore enforced the rules of discharging wastewater treated by septic tanks directly to a watercourse such as a river or a stream. Any septic tank that discharges directly to a watercourse such as a river or a stream will need to be replaced or upgraded to a sewage treatment plant or a package treatment plant. Wastewater discharged from a sewage treatment plant is safe, clean and permitted to be discharged into a watercourse. Our range of septic tanks has now been replaced with the more modern and efficient solution of Sewage Treatment Plants, all of which come with a life expectancy of over 20 years, so you can enjoy absolute peace of mind.
HydroClear GRP 6 Sewage Treatment Plant product image

HydroClear GRP 6 Sewage Treatment Plant

The GRP HydroClear 6 (HC6) can efficiently treat wastewater from bathrooms, toilets, laundry and kitchens before being safely discharged into a watercourse such as a river or a stream and drainage field. Wastewater discharged from the HC6 is absolutely safe and clean enough to be discharged into a watercourse or a drainage field. With a life expectancy of over 20 years, you can enjoy absolute peace of mind.

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CAP6 Sewage Treatment Plant product image

CAP6 Sewage Treatment Plant

The Harlequin CAP6 is a compact and small sewage treatment plant that is specifically designed for smaller residential homes with up to 6 people or 4 bedrooms. This powerhouse efficiently treats wastewater from bathrooms, toilets, laundry, and kitchen, ensuring an environmentally friendly solution for your septic system.

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HydroClear 6 Sewage Treatment Plant product image

HydroClear 6 Sewage Treatment Plant

The HydroClear 6 (HC6) is a compact and efficient domestic sewage treatment plant, ideal for small homes with up to 6 people. This system discreetly handles wastewater from your bathrooms, toilets, laundry, and kitchen, making it suitable for discharge into a watercourse, drainage field, or for further treatment if required.

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CAP9 Sewage Treatment Plant product image

CAP9 Sewage Treatment Plant

The Harlequin CAP9 sewage treatment plant is engineered for the efficient handling of domestic sewage within a compact system. It is suitable for households with up to 9 occupants or a 7-bedroom house, guaranteeing the treated water's safety for discharge into watercourses.

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Frequently Asked Questions

What Is a Septic Tank?

Septic tanks act as a vessel for sewage waste, with the associated dwell time allowing solids / sludge to fall to the bottom of the tank, while the liquid flows from the septic tank to a drainage field / soakaway.

Septic Tanks are suitable for specific applications where either further treatment or soil conditions can treat the outgoing untreated liquid. Only partial treatment occurs, with bacteria breaking down some solids. It’s typically used in rural areas or properties where centralised sewage treatment is not feasible.

What Is a Sewage Treatment Plant?

A sewage treatment plant provides a higher level of treatment than a septic tank. It usually involves multiple stages that involve mechanical and biological processes to break down and remove more organic matter and pollutants, before producing treated water that can be safely discharged.

Is It Difficult To Replace a Septic Tank With a Sewage Treatment Plant?

Replacing a septic tank with a sewage treatment plant involves several steps and considerations, and the ease of this process can vary depending on specific circumstances. Here are key factors that affect the complexity of the replacement:

  • Site Assessment: Initially, a thorough site evaluation is necessary. This includes understanding the size of the area, soil type, water table level, and accessibility for construction equipment.
  • Regulatory Compliance: Before proceeding, you must check local environmental regulations and obtain necessary permits. Different areas have varying rules about sewage treatment and discharge.
  • System Design and Selection: Choosing the right sewage treatment plant for your needs depends on the number of users, the environmental conditions, and the desired level of treatment. This step requires professional advice from an expert wastewater treatment team like us at Harlequin Manufacturing.
  • Removal of Old Septic Tank: This can be a complex task, particularly if the old tank is large or buried deep. Care must be taken to prevent contamination during removal.
  • Installation of New System: Installing a sewage treatment plant is generally more complex than a septic tank, despite having fewer mechanical parts, it still involves some complexity due to the necessary electrical components, including the power supply. Professional installation is highly recommended to ensure optimal functionality and compliance with relevant standards.
  • Landscaping and Restoration: After installation, the area may need landscaping or restoration work to return it to its original condition or to make it better.
  • Cost: Upgrading to a new system includes the cost of removal of the old tank and installation of the new system.
  • Maintenance Requirements: Finally, consider the maintenance requirements of the new system, which will be different from those of a septic tank.

Given these factors, replacing a septic tank with a sewage treatment plant can be a complex process and often requires professional assessment, installation, and maintenance. It requires a substantial investment of time, money, and expertise, but it does provide better functionality and efficiency in the long run.

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If you’d like to enquire about our range of Septic Tanks or simply need advice, do get in touch by filling this short form. Do include any additional information that would help us manage your query better. Alternatively, you can call us on +44 28 9261 1077.

Septic Tanks for Sale; UK and Ireland

At Harlequin Manufacturing, we’re dedicated to helping you find the optimal sewage treatment plant solution that not only meets your specific needs but also complies with eco-friendly waste management practices. We engineer a diverse range of specialist products, including advanced wastewater treatment plants for our clients throughout the UK and Ireland. 

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