The definitive guide...

Hutchinson Environmental Solutions’ definitive guide to the Environment Agency’s General Binding Rules for Small Sewage Discharges in England

Listed and explained one by one below are the Environment Agency’s General Binding Rules for Small Sewage Discharges.

Your legal obligations in respect of off-mains sewage and wastewater treatment are explained on numerous pages of the gov.uk website:

The Environment Agency (EA) is part of the Department for Environment, Farming and Rural Affairs (DEFRA). The EA operates only in England, where its main responsibilities are:

• regulating major industry and waste
• treatment of contaminated land
• water quality and resources
• fisheries
• inland river, estuary and harbour navigations
• conservation and ecology

Regarding water quality and resources, the EA work to reduce or prevent water pollution, preferably before there’s a pollution incident but also as soon as possible after one. If you cause water pollution, knowingly or unknowingly, the EA will act – as its mandate requires it to do - to stop and prevent further pollution. EA staff will try to work with you in the first instance and then against you if you fail to react or cooperate - whether that’s as an individual, as a group of individuals, or as a business.

The EA has jurisdiction over all water resources in England:

• fresh surface waters, e.g. lakes, tarns, streams, rivers and ponds, wherever they are
• marine surface waters, e.g. estuaries and coastal waters to 3 miles out
• groundwater, i.e. all water underground (even if it’s 1mm below the surface)

in order to protect and improve them in line with legislation.

Want to know more about the legislation around water pollution in the United Kingdom, Europe and internationally?

The EA uses General Binding Rules to protect water resources from pollution caused by Small Sewage Discharges as a quid pro quo for not having to apply for a permit. In making a Small Sewage Discharge without a permit, by the very fact of making the discharge you agree to be bound by the General Binding Rules. Ignorance of the General Binding Rules is not a defence, in the same way as not knowing the speed limit is 50mph is not a defence against breaking that limit.

Before we explain the rules in detail, here are the answers to the three most common questions.

1. Where can I discharge my treated sewage to?

  • Under the General Binding Rules, Small Sewage Discharges can be made without a permit to 3 types of “receptor”
    • fresh surface waters, e.g. inland lakes, tarns, streams, rivers and ponds, wherever they are (i.e. even if you built it yourself on your own land the EA still manages discharges into it)
    • marine surface waters, e.g. estuaries and coastal waters, to 3 miles out
    • groundwater, i.e. any and all water underground (even if it’s 1mm below the surface)

2. How much treated sewage effluent can I discharge under the General Binding Rules to one of these receptors?

  • discharges totalling less than 2000 litres of wastewater per day can be made from a septic tank or from a package sewage treatment plant “to ground”, and therefore sooner or later to groundwater, through a drainage field, infiltration field, leachfield, call it what you will, but what it’s most often called, incorrectly, is a “soakaway”
  • discharges totalling less than 5000 litres of wastewater per day can be made “to surface waters” from a package sewage treatment plant

3. What does 2000 and 5000 litres represent in terms of people’s daily wastewater production?

  • Wastewater production is accepted by the EA to be 150 litres/person/day in a domestic situation
    • 2000 litres equals 13 people’s domestic wastewater production per day
    • 5000 litres equals 33 people’s domestic wastewater production per day
  • Outside the home, e.g. in offices, hotels, cafes and restaurants, leisure centres, camping and caravanning sites with toilet blocks and showers, etc., the figure is not 150 litres/person/day: the total volume to be discharged per day must be calculated by site and at peak usage in high season by referring to British Water’s Code of Practice: Flows and Loads – 4: Sizing Criteria, Treatment Capacity for Sewage Treatment Systems, e.g.
    • in a rural office, 2000 litres could equal as many as 40 staff’s wastewater production per day – a large office
    • in a luxury hotel, 2000 litres could equal as little as 6 guest’s wastewater production per day – a very small hotel

4. Why is it wrong to call a drainage field after a septic tank or package sewage treatment plant a “soakaway”?

  • A soakaway’s purpose is only to attenuate the flow of rainwater into the ground. It offers no dispersal over a wider area or any form of treatment, rainwater being clean enough to soak away back into the water table without treatment.
  • A soakaway has traditionally been a rubble- or gravel-filled pit measuring approximately 1m x 1m x 1m for upto 100m2 of roof area. “Crates” are now often used to create the necessary supported underground void to fill with rainwater.
  • “Do crates work for sewage treatment?” No: why would they? It doesn’t matter what the soakaway is filled with, what matters is that a 1m x 1m x 1m soakaway concentrates the flow of water into the ground in a 1m2 area which quickly becomes saturated and therefore cannot support the aerobic microorganisms that digest the contaminants in the sewage.
  • “What about anaerobic bacteria?” Good question. Anaerobic bacteria are about 10 times slower than aerobic bacteria at doing the same job, so the wastewater would need to pass by them 10 times more slowly. But soil doesn’t just contain bacteria: it contains a whole food chain of microorganisms, all of which are aerobic, and it’s their total effort that’s necessary. And in the meantime, you have a soggy, black, foul-smelling wet patch in your garden, over your soakaway.
  • If a contractor builds you a soakaway for sewage treatment, you (and not the contractor) are contravening Building Regulations. Does that matter? Only when you come to sell your house and you either have to spend the money you should have spent in the first place to put it right or accept a lower price from the new purchaser for them to put it right.
  • If you use a rainwater soakaway in an attempt to treat sewage you will pollute the water table. How would you know? You probably wouldn’t because you can’t see the pollution. How do we know? Experience: we’ve dug them up, seen what they look like and know what that means in terms of effective physical and biological treatment.

The General Binding Rules explained, in order, one by one.

1.The discharge must be 2 cubic metres or less per day in volume [to ground]

  • See 2 above

2.The discharge must be 5 cubic metres or less per day in volume [to surface waters]

  • See 2 above, again.

3.The sewage must only be domestic [to ground and to surface waters]

  • Domestic sewage can be broadly summarised as sewage produced in activities that would normally be expected to occur in a domestic environment, e.g. bathing/showering/washing and personal hygiene, food preparation and cooking, washing up (by hand or with a dishwasher), going to the toilet, cleaning, laundry, etc. provided that the activities remain in proportion to the domestic scale. For example, a hotel, although it is a commercial enterprise, produces domestic sewage, as does a campsite, since the same activities occur in both of these as they do in the home and in more or less the same proportions as in the home. People still eat, wash up, shower, go to the toilet, etc. when they’re camping, or when they stay in a hotel.

  • Even though a restaurant or a fast-food takeaway is produces a higher proportion of food than in the home, the characteristics of its wastewater don’t present any difficulties for effective treatment provided that other regulatory requirements are met, i.e. the provision and maintenance of a suitably sized and correctly installed grease management system, and that good housekeeping and kitchen management is practised.

  • Where the characteristics of the wastewater differ in volume, strength, composition, etc. from domestic sewage, usually in the pursuit of a single industrial purpose, e.g. a pizza factory or a paper-making plant, it becomes an industrial or trade effluent.

4.The discharge must not cause pollution of surface water or groundwater [to ground and to surface waters]

5.The sewage must receive treatment from a septic tank and infiltration system (drainage field) or a sewage treatment plant and infiltration system [to ground]

  • When you discharge “to ground” through a drainage field, the upstream septic tank or package sewage treatment plant is only part of the whole treatment system; the other part is the drainage field itself.

  • A septic tank separates 30-40% of the pollutants contained in sewage by settlement and flotation; it retains these solids for later removal and disposal elsewhere (see GBR 12). This separation process is called primary treatment. The resulting primary-treated partially clarified liquid flows on into the constructed drainage field where the remaining 50-70% of the pollutants are removed by secondary biological treatment before it reaches any groundwater.

  • The mechanics of this are achieved firstly by distributing the partially clarified liquid from the septic tank as evenly as possible by gravity over an area of ground large enough to accept the flow/volume concerned and secondly by controlling the rate of infiltration of the partially clarified liquid into that ground. Just how quickly or how slowly liquid will soak away into the ground – the ground’s porosity - is a critical factor in working this out. The ground’s porosity is established by carrying out percolation tests.

  • The principal purpose of the drainage field is not “getting rid” of the partially clarified liquid as fast as possible but of making sure it is adequately treated so that it doesn’t have a detrimental impact on the quality of any groundwater or surface water that it will eventually find its way back to. You’re trying to avoid this:

  • You might not see the effects of polluting the groundwater in this way - or you might not care. If you’re not bothered for yourself do you consider others’ health.

  • If your own children, grandchildren or relatives aren’t enough of an incentive not just to “do the right thing” but to abide by the law and money is your only motivator, think about how much the clean water in your tap costs, and how much less it would cost if you didn’t pollute it so badly to make it need cleaning so much.

  • Adequate treatment is assured by carrying out the percolation tests accurately and then constructing the drainage field correctly, using the right materials. Out of sight underground should not be out of mind.

  • Treatment plants offer primary and secondary biological treatment in a single tank. They are far more effective than septic tanks: under test conditions they remove – or, more accurately, convert - broadly speaking, between 80 and 95% of the pollutants in sewage into simpler, less polluting chemical compounds when operating correctly. This is recognised by allowing them a 20% smaller drainage field than a septic tank serving the equivalent number of people. You might think that, given their effectiveness, it should be a greater saving but treatment plants themselves generate organic solids, in the form of dead bacterial husks, that then need to be filtered out of the discharge in a drainage field. (It does beg the question why bother with a treatment plant in the first place if you’re discharging to the ground, to which there are a number of responses).

6.The sewage must receive treatment from a sewage treatment plant [to surface waters]

  • Only the secondary, biologically treated effluent from a package sewage treatment plant is of a high enough quality to be discharged to surface waters (and only then if the plant is regularly maintained and not abused).

  • New septic tank installations are not allowed to discharge to surface waters (and have not been allowed to do so in England for many years).

  • All septic tanks in England that do discharge to a beck, a stream, a river, a pond, a lake or any other form of surface waters, must be upgraded to package sewage treatment plants by the beginning of 2020. Specifically, the gov.uk webpage reads:

"If you have a septic tank that discharges directly to a surface water you will need to replace or upgrade your treatment system by 1 January 2020, or when you sell your property if before this date."

Don't believe it?

  • There is no requirement to replace, wholesale, all septic tanks with package sewage treatment plants by 2020, as some either less-than-scrupulous or otherwise less knowledgeable businesses are claiming.

  • If your septic tank discharges to a land- or field drain that discharges to surface waters – and many do, thanks to the actions of well-intentioned digger drivers trying to solve the problem of backed-up foul drains and soggy gardens over the years - then it must be replaced because it is discharging to surface waters.

  • Why has the Environment Agency sprung this upon us? They haven’t. It was announced – albeit very quietly, due to a lack of promotional funds (there was a lot of flood damage to repair from late 2009) - in 2010, with a 10 year period of grace.

  • Are there any grants available? No, there are no public funds or grants available to facilitate the replacement of a septic tank with a package sewage treatment plant, due to a lack of funds (there was a lot of flood damage to repair from 2012 and late 2015, and EA funding has reportedly been cut by 25% in real terms since 2009). Don’t shoot the messenger…

7.The discharge must not be within a groundwater Source Protection Zone 1 or within 50 metres from any well, spring or borehole that is used to supply water for domestic or food production purposes [to ground]

  • To be 100% certain, you can call the Environment Agency on 03708 506 506 to ask them.

8.For discharges in tidal waters, the discharge outlet must be below the mean spring low water mark [to surface waters]

  • Self-explanatory.

9.All works and equipment used for the treatment of sewage effluent and its discharge must comply with the relevant design and manufacturing standards i.e. the British Standard that was in force at the time of the installation, and guidance issued by the appropriate authority on the capacity and installation of the equipment [to ground and to surface waters]

  • Installing a new septic tank to replace an existing septic tank, installing a package sewage treatment plant to replace a septic tank, installing a package sewage treatment plant to replace another package sewage treatment plant, or constructing a new drainage field to replace a failed drainage field all require Building Control approval because all are material alterations to controlled services. It should ensure that the work is carried out to a minimum acceptable technical standard and is fit for purpose.

  • When you come to sell your house, you are now asked if you’ve done any work to it. If you have, you need to be able to prove it was done to the regulations in force at the time. If you can’t prove it, you will either have to prove it retrospectively, which is expensive because Building Control may want you to dig things up to see for themselves what’s been done, or you could accept a lower offer price on your property, to the value of proving the works comply, plus perhaps a little for inconvenience. Note that the works will have to comply with current standards and regulations, not the standards and regulations in force at the time the work was carried out. You could, of course, tell “ a little white lie, no harm done” – although if you’re selling your property you’re probably buying another, so you’d have to hope that your vendor hasn’t done the same…

  • As these very words were being written, we were called by someone selling their house. Their replacement drainage field, installed 11 years ago and serving a septic tank, has been built too close to a stream. Their prospective purchaser’s solicitor has noticed this. The vendor wanted to know what to do. All that can be done is to replace the septic tank with a package sewage treatment plant, or build a new drainage field that’s more than 10m from the stream. Approximate cost? From experience, £8,000-10,000 plus VAT. If the caller’s installer had read and followed the requirements in the British Standard BS 6297:2007+A1:2008 Code of practice for the design and installation of drainage fields for use in wastewater treatment it would have saved the caller (and probably himself now) a lot of time, expense and frustration.

  • Most septic tanks are designed, manufactured, tested and approved to BS EN 12566-1:2000 Small wastewater treatment systems for up to 50 PT. Prefabricated septic tanks. If you want to install one that’s not, you will have to apply for a permit.

  • Most package sewage treatment plants are designed, manufactured, tested and approved to BS EN 12566-3:2005+A2:2013 Small wastewater treatment systems for up to 50 PT. Packaged and/or site assembled domestic wastewater treatment plants. If you want to install one that’s not, you will have to apply for a permit.

  • Draw your own conclusions if your contractor/installer/supplier doesn’t work to these standards or, more disturbing, isn’t even aware of them.

10.The system must be installed and operated in accordance with the manufacturer’s specification [to ground and to surface waters]

  • Manufacturers produce simple installation guidelines and operation and maintenance (O&M) manuals, all of which need to be observed to maintain warranties offered.

11.Maintenance must be undertaken by someone who is competent [to ground and to surface waters]

  • “Competence” in off-mains wastewater treatment field can be defined as someone who has been trained in and/or has practical experience of, and understands, the mechanical, electrical and, most importantly, the biological processes involved in the treatment of sewage, rather than someone who’s “willing to have a go”, even with the best intentions.

  • Competence can be achieved by attending a British Water Accredited Engineer’s training course. A list of such competent engineers is maintained on the British Water website, which you can access to check.

  • We stress the biological aspect of sewage treatment enormously because that, ultimately, is the purpose of this whole exercise: the vessel, the mechanics, the electrics, the design - everything else is just supports an effective treatment process. If the treatment process itself is not working, you want someone who can diagnose what that is and implement some corrective action.

12.Waste sludge from the system must be safely disposed of by an authorised person [to ground and to surface waters]

  • Authorised in this case means having a waste carrier’s licence to transport controlled waste between its source and its legal place of disposal, in this case and for the most part the local municipal wastewater treatment plant. A farmer’s field, via the slurry pit or by immediate application to land, is not considered a legal place of disposal, and makes a mockery of all the measures put in place so far.

  • Desludging the septic tank or treatment plant ensures not only its effective continued operation, it also prevents solids from entering the watercourse and polluting it or from entering the drainage field and blocking it up, causing the partially treated sewage to appear on the ground surface, usually in black, smelly pools. There’s a useful British Water Code of Practice: Guide to the Desludging of Sewage Treatment Systems.

13.If a property is sold, the operator must give the new operator a written notice stating that a small sewage discharge is being carried out, and giving a description of the waste water system and its maintenance requirements [to ground and to surface waters]


  • When a property is sold any solicitor worth their salt will ask for this and any estate agency/panel surveyor worth their salt will realise the impact that a poorly installed, badly maintained system will have on a property’s value.

  • If you’re buying a house with an on-site sewage treatment system and want to know about its condition before you proceed, contact us. We don’t charge for advice over the phone

14.The operator must ensure the system is appropriately decommissioned where it ceases to be in operation so that there is no risk of pollutants or polluting matter entering groundwater, inland fresh waters or coastal waters [to ground and to surface waters]

  • This basically means disconnect and desludge the system if it is to be abandoned so that it cannot be used inadvertently without maintenance in the future. Fill it in with inert material so that it isn’t left as a void in the ground, with no indication at surface level of the dark unpleasant hole below.

15.New discharges must not be within 30 metres of a public foul sewer [to ground and to surface waters]

  • Self-explanatory: always connect to a mains sewer if possible, even way over 30m away.

16.For new discharges, the operator must ensure that the necessary planning and building control approvals for the treatment system are in place [to ground and to surface waters]

  • A new discharge is, as you might expect, one to where a discharge has not been made before. That means an extension to an existing failing drainage field, a new drainage field adjacent to an existing failed drainage field, a drainage field discharge to ground converted to a discharge to surface waters because the drains are backing up (in which case if you have a septic tank then you need to upgrade it to a package sewage treatment plant).

  • Note that it’s the operator’s responsibility to fulfil this rule, not the supplier’s or the installer’s. Good customer service and commercial responsibility dictates that a responsible provider makes the client aware, of course. The EA has a long definition of what an operator is.

  • Building Regulations have been covered under General Binding Rule 9, and the guidance there is clear. Planning is a different matter altogether. What follows is more a summary of our experience rather than specific advice and is more to prepare you for what you might have to face.

  • The following is the content of an email received from a Local Planning Authority. It explains the situation very well, hence its reproduction in full. The question was, “Is planning permission necessary to replace a septic tank with a package sewage treatment plant when the only visual change is the type and location of one, possibly two, manhole covers?”

    • “You are correct in that planning permission assesses visual impact where development of or change to buildings is proposed however, there is also a requirement under planning legislation for the Local Planning Authority (LPA) to assess any proposed development. The text below is an extract from the Planning Practice Guidance webpage which clarifies the definition of ‘development’ and includes Engineering Operation (groundworks) within that definition. The installation of a septic tank/sewage treatment plant would fall under this category and as such, would require planning approval.

    • The LPA are responsible for managing the use and development of land and buildings. The overall aim of the system is to ensure a balance between enabling development to take place and conserving and protecting the environment and local amenities. There are a number of different sorts of assessment required but unfortunately, due to the complexities of the legislation and the various kinds of development, it is not possible to give a short summary of these. The ‘Plain English Guide to Planning’ document should assist you in this matter and will, I hope clarify the process.

    • Extract from ‘Planning Practice Guidance:

    • Planning permission is only needed if the work being carried out meets the statutory definition of ‘development’ which is set out in Section 55 of the Town and Country Planning Act 1990.

    • Development’ includes:

    • building operations (e.g. structural alterations, construction, rebuilding, most demolition);
    • material changes of use of land and buildings;
    • engineering operations (e.g. groundworks);
    • mining operations;
    • other operations normally undertaken by a person carrying on a business as a builder;
    • subdivision of a building (including any part it) used as a dwellinghouse for use as two or more separate dwellinghouses

    • The categories of work that do not amount to ‘development’ are set out in Section 55(2) of the Town and Country Planning Act 1990. These include, but are not limited to the following:

    • interior alterations (except mezzanine floors which increase the floorspace of retail premises by more than 200 square metres)
    • building operations which do not materially affect the external appearance of a building. The term ‘materially affect’ has no statutory definition, but is linked to the significance of the change which is made to a building’s external appearance.
    • a change in the primary use of land or buildings, where the before and after use falls within the same use class.”

  • Another Local Planning Authority was asked to refer us to the source of the following statement made in a guidance document they published, and if the guidance is still valid (no response a week later):

    • "Provision of a new or replacement septic tank or packaged sewage treatment plant may require Planning Permission, unless it is to serve a single dwelling, within the property boundary and not located between the house and the highway.”

  • The same authority, when consulted previously, informally and verbally, on the requirement for planning permission to replace a septic tank with a package sewage treatment plant, said that it wasn’t necessary because it couldn’t really be seen from the very minor adjacent road.

  • It’s quite easy to find planning applications on Local Planning Authority websites solely, and most commonly, for the replacement of a septic tank with a package sewage treatment plant, but the number of planning applications falls far, far short of the number of treatment plants and septic tanks sold in England.

  • The planning process does perform another function: the engagement of “statutory consultees” whose responsibilities the general public may be impacted.

  • Amongst the statutory consultees relevant to the prevention of water pollution which may be detrimental to human health, wildlife and the environment generally are Environmental Health, the Environment Agency and Natural England. (Note that it was the current government through Defra that resuscitated the General Binding Rules at the start of 2015 as being “less burdensome” to business and individuals.)

17.New discharges must not be in or within: 500 metres of a Special Area of Conservation (SAC), Special Protection Area (SPA), Ramsar site, biological Site of Special Scientific Interest (SSSI), freshwater pearl mussel population, designated bathing water, or protected shellfish water; 200 metres of an aquatic local nature reserve; 50 metres of a chalk river or aquatic local wildlife site [to surface waters]

  • How could you be sure of any of the above? Applying for planning permission will ensure consultation with the necessary bodies, but you or your architect might want to know what you’re facing. We use a mapping system that will give you a very good indication, so you could contact us, and we’d be happy to hear from you. We can also prepare and submit your application for a permit to the EA if you don’t have the time or specific experience to do it yourself. If you do want to do it yourself, the forms are below. Beyond that we can advise you what sort of systems are available to meet the treated effluent discharge quality standards that may be required in a sensitive location.

18. New discharges must not be in, or within 50 metres of, a Special Area of Conservation (SAC), Special Protection Area (SPA), Ramsar site, or biological Site of Special Scientific Interest (SSSI), and must not be in an Ancient Woodland [to ground]

  • See above

19.New discharges must be made to a watercourse that normally has flow throughout the year [to surface waters]

  • Although a package sewage treatment plant removes far more pollutants and contaminants than a septic tank, what comes out of it is by no means Evian, even if it might be “as clear as gin.” It still contains pathogens - disease-causing microorganisms in the form of bacteria and viruses – and enough pollutants and contaminants still to represent a public health risk and cause unpleasant odours and environmental damage if they’re not diluted and transited away by oxygenated, flowing water. It may be that the stinking, stagnant ditch to which you discharge isn’t close enough to your property to affect you but it might be close enough to someone else’s to affect them.

20.For new discharges, any partial drainage field must be installed within 10 metres of the bank side of the watercourse [to surface waters]

  • The logic behind this rule is to maintain a distinction between discharges to ground via a drainage field, which require a permit at a lower volume because of the potential impact on groundwater, and discharges to surface waters, which have a higher volume threshold for permitting because of the dilution, transit and oxygenation afforded by flowing water. If you were to install a “seasonal soakaway”, i.e. a slotted pipe in an infiltration trench that leads to a watercourse you’re discharging both to groundwater and to surface water, depending on the seasonal ground conditions. The EA considers that having only the last 10m of a treated effluent discharge pipe as a “partial drainage field” (i.e. slotted pipe) is close enough to the water course to be defined as a discharge to surface waters.

21.New discharges must not be made to an enclosed lake or pond [to surface waters]

  • Even well-treated effluent still has a detrimental effect on the dissolved oxygen content of the receiving water course, i.e. it can still have a negative impact on the “receptor”, especially if it is allowed to build up. In a flowing water course oxygen is continually entrained in the water which allows the bacteria that continue to reduce the pollutant load to respire; in a still lake or pond that doesn’t happen. What oxygen there is is used up quickly and anaerobic processes (they’re the very smelly ones) take over.

  • Nutrients such as nitrates and phosphates in the wastewater facilitate the growth of algae on the surface which, although it produces oxygen in daylight, blocks sunlight to the water below to stop the same process in plants beneath the surface. When the algae dies, as it will, it decays and becomes a source of “organic load” – pollution, in this context – causing eutrophication.

We hope this helps you, whether you’re looking to build a new house without access to mains sewerage, an architect designing someone’s dream home, buying a house with a septic tank or are already the owner of a problematic package sewage treatment plant. If you have any questions or would like some impartial advice on how to treat your wastewater responsibly and effectively please do just get in touch: the benefit of our experience over the phone is free, as is a site visit if you really want one. In England we concentrate our domestic installation work in and around our home county of Northumbria, so Cumbria, Durham, Tyne and Wear, Cleveland, north, east and west Yorkshire and across into Lancashire. Although travelling further afield costs more our national clients tell us that we still offer very good value for money and peace-of-mind for more involved commercial installations on difficult sites where compliance is critical.

So, how can we help you?

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