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Understanding Part H Building Regulations: What It Means for Wastewater Treatment Systems

When planning a new build or upgrading an existing drainage system in the UK, understanding Part H of the Building Regulations is essential—especially if your project includes a wastewater treatment plant, septic tank, or drainagefield system.

In this blog, we’ll break down what Part H covers, how it applies to wastewater treatment systems, and what you need to know to stay compliant.

🔍 What Is Part H of the Building Regulations?

Part H – Drainage and Waste Disposal is one of the approved documents under UK Building Regulations. It provides guidance on the design, installation, and maintenance of drainage systems for domestic and commercial properties.

The document is split into several sections:

  • H1: Foul water drainage

  • H2: Wastewater treatment systems and cesspools

  • H3: Rainwater drainage

  • H4: Building over sewers

  • H5: Separate systems of drainage

  • H6: Solid waste storage

For those working with wastewater treatment systems, Sections H1 and H2 are the most relevant.

💧 What Does Part H Say About Wastewater Treatment?

H1: Foul Water Drainage

This section emphasises that all buildings must have an adequate system for the disposal of wastewater from toilets, bathrooms, kitchens, and utility rooms.

Where mains drainage is available, connection to the public sewer is always the preferred option. However, when a mains connection isn’t feasible—typically in rural or remote areas—an alternative method such as a septic tank or packaged sewage treatment plant is permitted under H2.

H2: Wastewater Treatment Systems

Here’s what H2 outlines for off-mains drainage solutions:

  1. Hierarchy of Drainage Options
    The regulation sets out a "hierarchy" for selecting a drainage method:

    • Public sewer (where available)

    • Packaged treatment plant (preferred over septic tanks)

    • Septic tank

    • Cesspool (only as a last resort)

  2. Discharge Permits and Environmental Considerations
    Any system discharging to surface water or ground must comply with the Environment Agency’s General Binding Rules, and in some cases, a discharge permit may be required.

  3. System Capacity and Design
    The treatment system must be appropriately sized based on the number of people using it (Population Equivalent or PE). It must also be:

    • Located to avoid contamination of watercourses or drinking water sources

    • Installed with adequate ventilation and access for maintenance

    • Positioned at a safe distance from buildings and boundaries (e.g., typically at least 7m from a dwelling and 10m from a watercourse or soakaway)

  4. Drainage Field Design
    Where effluent is discharged to the ground, a properly designed drainage field must be installed, complying with BS 6297 standards. This includes percolation tests to determine ground suitability.

🏗️ When Is Building Control Approval Required?

Building Control must be notified if:

  • You're installing a new septic tank or sewage treatment system

  • You're upgrading or replacing an existing system

  • You're connecting to a new or existing discharge point (e.g., new drainage field or outfall)

  • You're changing the position of drains or access covers

In many cases, a Building Control Officer will need to inspect the system both during and after installation to ensure it complies with Part H.

📋 Additional Tips for Compliance

  • Use certified products: Make sure any treatment plant or septic tank is UKCA marked and complies with EN 12566-3 standards.

  • Hire qualified installers: Work with professionals who understand the regulations and can provide the right documentation.

  • Plan ahead: Site access, ground conditions, and distances from watercourses can all affect your options and costs.

  • Maintenance is key: Regular emptying and servicing is not only good practice—it’s part of your legal obligation for keeping the system effective and safe.

✅ Summary

Part H of the Building Regulations plays a crucial role in ensuring that wastewater is handled safely and responsibly. Whether you're a homeowner, developer, or installer, staying compliant is not just about ticking boxes—it’s about protecting people, property, and the environment.

If you’re planning a new system or need help upgrading an existing one, our expert team at Direct Drainage is here to help. We supply a wide range of Klargester, Clearwater, WPL, Graf, Tricel, Harlequin and other leading wastewater treatment systems, along with all the technical advice you need to meet regulations.

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