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Building Regulations Part H


Reading time: 8 minutes


What is Part H of the Building Regulations?

The Building Regulations Part H - drainage and waste disposal (also known as Approved Document H) gives in-depth information on drainage, surface water and foul (waste) water in both homes and non-dwellings. The Part H Building Regulations has technical guidance on workmanship and materials for drainage and waste disposal, covering sewage pipes, treating wastewater, septic tanks, storing solid waste and installing hygienic pipework. Approved Document H also discusses building over and around existing sewers.


Building Regulations Part H is split into 6 main 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


Part H tells you how to comply with the latest Building Regulations for building work in England - including extensions, new builds and most conversions - as well as excepted energy buildings in Wales


Have there been any changes to the drainage and waste disposal Building Regulations?

The Building Regulations Part H (drainage and waste disposal) took effect on 1st October 2015, following updates from the 2002 edition. The latest changes in 2015 were:

  • New guidance on solid waste storage (part H6) and

  • New limits to part H3 following updates to Approved Document M


What is requirement H1 and H2 of the Building Regulations Part H?

Parts H1 and H2 relate to foul water drainage (H1) and wastewater treatment (H2), including cesspools. H1 states that ‘an adequate system of drainage shall be provided to carry foul water’ (meaning waste water from appliances, water from the kitchen sink and sanitary waste including toilets and bidets) in the building to one of the following:

  • A public sewer

  • Private sewer

  • Septic tank

  • Cesspool

H1 gives detailed trap and seal measurements, pipe materials, safe connections and ventilation pipe diagrams. H1 also discusses materials and workmanship for foul water in detail. Pipes, fittings and joints should withstand an air test of at least 28mm. Every trap should maintain a water seal of at least 25mm. A pressure water test is also needed for pipes up to 300mm. The Part H Building Regulations can alternatively follow BS EN 12056.


H2’s wastewater treatment systems and cesspool info covers properties which aren’t connected to a main public sewer. H2 states that it must:

  • Not harm people’s health

  • Not contaminate water supplies

  • Have access for maintenance and emptying

  • Still function during a power failure

  • Be waterproof

  • Have a large enough capacity

  • Have proper ventilation

  • Notice must be put in the property to alert users of the septic tank/cesspool


Section H2 in Part H of the Building Regulations covers drainage fields and drainage mounds, in both design and construction, to give secondary treatment for properties with septic tanks or package treatment plants. Drainage fields or mounds must:

  • Be at least 10m away from drains and watercourses

  • Be at least 50m from the ground water supply

  • Be 15m or more from any building

  • Be far enough away from other soakaways to not go over the ground’s soakage capacity

  • Be downslope of water sources

  • Not be near water supply pipes

  • Not be put near roads, driveways or paved areas


What is requirement H3 of the Part H Building Regulations?

H3 relates to drainage of paved areas, and covers design and materials to make sure small car parks and patios or driveways up to 4,000m2 divert or drain water away from the buildings. The document refers to rainfall intensities and flooding risk in different areas of England. As well as using porous paving, the Part H drainage and waste disposal guidelines suggest the use of gullies, outlets, drainage channels and soakaways.


What is requirement H4 of the Building Regulations?

Section H4 of the Building Regulations Part H covers building over sewers, drains and disposal mains, during extensions and new projects, to ensure that the work doesn’t damage the sewer and still leaves access for maintenance and repair. The work must not overload the drain, and H4 includes in-depth guidance on diverting sewers when needed. A developer must contact the drain owner before work starts, as well as getting the relevant permission from the water company or sewage company which operates the sewers.


What is requirement H5 and H6 of the Building Regulations?

H5 (separate systems of drainage) and H6 (solid waste storage) are discussed in detail in the Part H document. H5 covers separate foul water and rain water drainage, as well as contaminated runoff, and states:

  • ‘Any system for discharging water to a sewer…shall be separate from that provided for the conveyance of foul water from the building’.


H6 deals with the design and location of solid waste storage, and says:

Section H6 of the drainage and waste disposal Building Regulations covers both domestic and non-domestic buildings.

Do I need building regs for a new drainage?

All new builds and extensions which involve pipes and drainage must conform to Building Regulations. If you’re renovating a home or changing its use, and are moving sinks, baths, toilets or installing new pipes, you’ll usually need Building Regs approval too. Any alterations to outside drainage or septic tanks will need to conform to Part H of the Building Regulations and will need to be signed off by an approved Building Control Officer (BCO) or inspector. 


What is the law on land drainage?

The Land Drainage Act 1991 says that a watercourse must be maintained by its owner to make sure that it’s in good condition and is free-flowing. Section 23 of the Land Drainage Act states that property owners and developers must have approval from the relevant local authority before obstructing, changing or diverting a watercourse - either permanently or temporarily. This also usually includes repairs and maintenance. The Building Regulations Part H covers the need to separate pipe systems for waste or rain water, as well as how to build over or divert a sewer once permission is given.


Normally, wastewater pipes (or foul water pipes) should not be connected to the rainwater system, to avoid contamination and/or flooding if the drain is overwhelmed. If rainwater does drain from a property to a public sewer, you might be charged by the water company as part of your water drainage bill.

You can find more information on all the current Building Regulations on our dedicated Travis Perkins Building Regs hub.


Disclaimer: Information displayed in this article is correct at the time of publication, but note that legislation changes periodically. Please refer to the latest publication of each approved article. The information contained on this page is intended as an overall introduction and is not intended as advice from a professional building control officer. The definition of ‘building work’ and when Building Regs approval is required is set out here. Travis Perkins aims to avoid, but accepts no liability, in the case that any information stated is out of date. Always consult the approved local authority building control team when considering any exemptions, and before undertaking any work.