Building Regulations Approved Document H: Drainage and Waste Disposal Standards Explained

Building Regulations Approved Document H sets out the legal requirements for drainage and waste disposal in buildings across England and Wales. Whether you are constructing a new property, extending an existing one, or upgrading your plumbing systems, understanding these regulations is essential to ensure your drainage infrastructure is safe, functional, and compliant. This document covers foul water drainage, rainwater disposal, and solid waste storage, making it one of the most important regulatory documents for any construction project.

Approved Document H is divided into six distinct sections covering foul water drainage, wastewater treatment systems, rainwater drainage, building near existing sewers, separate drainage systems, and solid waste storage. By following these regulations, homeowners and builders can prevent health hazards, avoid structural damage, and protect the environment. This guide explains each section in practical terms so you can apply the rules to your own project.

H1: Foul Water Drainage Requirements

Foul water is defined as water that has been used for sanitary purposes, including wastewater from toilets, bidets, washing machines, and kitchen sinks. Section H1 requires that every building must have adequate means for draining foul water away safely. The preferred method is connection to a public sewer, but alternative options are permitted when this is not feasible.

The approved methods for foul water disposal, in order of preference, are:

1. Connection to an existing public sewer
2. Connection to a private sewer that feeds into the public system
3. Discharge into a septic tank or wastewater treatment system
4. Disposal into a properly constructed cesspool

When designing a foul water drainage system, several performance requirements must be satisfied. The system must minimise the risk of blockages and leakages, prevent foul air from entering the building, and ensure adequate ventilation throughout. Every discharge point must incorporate a water seal trap that retains at least 25mm of water, preventing odours from escaping back into the living space. These traps must be accessible for cleaning in case blockages occur. If your project involves connecting new pipework to existing drains, read our guide on how to connect waste pipes to main drainage systems for practical installation advice.

The regulations also specify that pipework diameters must be suitable for the expected volume of use and that ventilation pipes must be integrated to maintain airflow and prevent pressure fluctuations that could compromise trap seals. For larger buildings with multiple storeys, additional design considerations apply, including properly sized discharge stacks and branch pipework configurations.

H2: Cesspools and Wastewater Treatment Systems

When connection to a public sewer is not possible, section H2 provides guidance on alternative wastewater treatment solutions, including septic tanks, sewage treatment plants, and cesspools. These systems must be designed and installed to strict standards to protect public health and the environment.

Any septic tank, cesspool, or treatment system must satisfy the following requirements:

• It must not pose a risk to the health of any person living or working nearby
• It must not contaminate any water supplies, including groundwater sources
• It must provide adequate access for maintenance, cleaning, and emptying
• It must remain operational during power cuts if it relies on electrical components
• It must not be located in an area susceptible to flooding

The tank or storage vessel must be of sufficient capacity, constructed to prevent leaks and ingress of groundwater, and fitted with suitable ventilation. One important requirement often overlooked is the need for a permanent notice displayed in a prominent position near the system explaining how it operates and should be maintained. Regular preventive pipe maintenance is also essential to keep wastewater systems functioning properly and avoid costly blockages.

H3: Rainwater Drainage Standards

Effective rainwater drainage is critical to protecting a building from damp and structural damage. Section H3 sets out the standards for draining rainwater from roofs, paved areas, and surrounding land. If rainwater is not properly managed, it can saturate walls, penetrate cavities, and cause thousands of pounds worth of damage through rising damp, mould growth, and foundation instability.

The regulations specify that rainwater must be drained away from buildings using one of the following methods, listed in order of preference:

1. A soakaway system that allows water to percolate into the ground
2. A natural watercourse such as a stream, river, or ditch
3. A public surface water sewer
4. A combined sewer (only where separate systems are not available)

The size and fall of gutters, downpipes, and underground drainage runs must be calculated based on roof area, local rainfall intensity, and surface type. Paved areas around the building also fall under these regulations, as they generate significant surface runoff. Proper gutter cleaning and maintenance ensures rainwater is effectively channelled away from the building fabric.

Rainwater harvesting systems, which capture rainfall for reuse, are exempt from certain requirements of section H3. However, they must not compromise the primary drainage function. Where drainage systems serve extensions or new buildings, the design must be submitted for building control approval before work begins.

H4: Building Near or Over Existing Sewers

When carrying out construction work such as extensions, underpinning, or groundworks, section H4 requires that existing drains and sewers must not be damaged or disturbed. Damage to a sewer can cause pollution, subsidence, and serious health risks. Before starting any excavation, check whether any drains or sewers run beneath your site.

The Sewerage Undertaker maintains records of sewer locations under section 199 of the Water Industry Act 1991. These should be consulted during the planning phase. If a drain or sewer is found on your site, discuss the situation with your architect, local authority, and building control office to determine the best approach.

The protection measures required depend on the depth and position of the sewer:

During construction, barriers should be erected to protect drains from heavy machinery. If you are planning an extension near a sewer, check whether you need planning permission for home improvement projects before proceeding.

H5: Separate Drainage Systems and H6: Solid Waste Storage

Section H5 establishes a fundamental principle of modern drainage design: foul water and rainwater must be kept in completely separate systems. Rainwater cannot drain into the foul water system, and foul water cannot be discharged into surface water drains. This separation prevents sewage overflows during heavy rain and ensures treatment plants receive only the waste they are designed to process.

The requirement for separate systems applies particularly to extensions where surface water can drain into a mapped sewer or one being constructed by the sewage undertaker. Meeting the regulations requires that:

• The rainwater is not contaminated by foul waste
• The drainage connects into a public system with separate foul and surface water sewers, or one under construction

Your architect and local authority can help determine the most suitable system. In buildings with bathroom extractor fans and ventilation systems, proper drainage separation ensures moist air and wastewater are handled correctly without cross-contamination.

Section H6 addresses the storage and removal of solid household waste. Suitable space and amenities must be provided, and residents must have adequate access to deposit waste and for collection services to retrieve it. The requirements vary by building type:

• Domestic low-rise buildings (houses and flats up to four storeys): Must have space for separate bin storage or at least two communal storage containers, with sizes agreed with the Waste Collection Authority.
• Domestic high-rise buildings (over four storeys): Flats up to the fourth floor can have individual waste storage. Above the fourth floor, a single chute-fed unit should be provided for non-recyclables, with separate storage for recyclables.
• Non-domestic buildings (shops, offices): Discuss with the Waste Authority how waste types will be separated, what volumes are expected, fire risks, hygiene, and where storage will be located.

The Waste Collection Authority can specify bin type and number under sections 46 and 47 of the Environmental Protection Act 1990. Where damp issues below damp proof course level are a concern, ensuring waste storage areas are properly drained and ventilated can help prevent moisture problems.

Practical Compliance Tips

Ensuring compliance with Approved Document H requires careful planning from the earliest stages of your project. Determine the most appropriate drainage solution based on proximity to public sewers, soil conditions, and local authority requirements. Early consultation with building control is strongly recommended to identify potential issues before construction begins.

When designing your drainage system, pay close attention to pipe gradients, access points for rodding and cleaning, and proper ventilation. Every system must include inspection chambers at key junctions and changes of direction to allow for maintenance. The minimum pipe diameters in the regulations should be treated as the lower limit, not a recommended size.

For properties with cavity wall insulation and damp prevention measures, coordinate drainage and wall construction to avoid bridging the damp proof course. All pipework passing through walls should be properly sleeved and sealed.

Approved Document H is updated periodically. Always check you are referencing the most current version before finalising your plans. Your local building control office can provide guidance on recent amendments. Following these regulations protects the long-term value and safety of your property. For guidance on building tools and construction techniques that can help with drainage installations, explore our library of practical guides.