What you need to know about the changes to off mains drainage

Anyone with a septic tank, or any type of off mains drainage, will need to brush up on the dramatic changes to environmental law effective from January 2020. In the most read article of the week published on probuildermag.co.uk, Mark Grantham of Lincolnshire Drainage Solutions explains all.

Most builders will have clients with off mains drainage, rural properties, businesses such as pubs, golf courses– the list is endless. All will be affected by the new rules and need the help of builders to get compliant.

The key objective of the law change is to prevent untreated sewage effluent entering our watercourses. Currently it is illegal to discharge effluent from a septic tank to a watercourse, and has been since the current law came into force in 2015. This issue has been hugely under published and the date of January 2020, when everyone is expected to have made the required changes to become compliant, is barely six months away. People currently selling a property with off mains drainage are discovering these changes as conveyancing solicitors are insisting on compliance with the General Binding Rules now.

Without compliance the property sale cannot proceed, and this is coming as a massive shock to most vendors. Unfortunately, most existing systems fail to meet the requirements in some way. Many clients presented with this issue are going to pick up the phone to their regular builder, or a contractor, locally known for this type of work for assistance.

This is potentially a huge source of work for builders and groundworkers across the country. The scale of the amount of work needed for all off mains drainage systems to comply with new regulations is massive and hardly anyone has yet become compliant unless selling a house, or are perhaps aware of the changes for environmental reasons, such as rural estates and farms anxious not to breach their own environmental rules.

Builders’ merchants across the country have a huge range of products available in order to provide a compliant solution. The leaders in manufacturing these products are UK based and, through the local merchant networks, builders can access technical support to ensure they advise clients correctly. Most of the leading suppliers offer on-site support and have hugely knowledgeable staff out on site advising builders.

Each individual situation will present different challenges to achieve compliance, a typical scenario of a rural property with an existing septic tank discharging its output/effluent to a watercourse could possibly be solved and compliance achieved in several ways, subject to the circumstances and conditions on site. If there is sufficient space on site it could be as simple as constructing an appropriately designed and installed “infiltration field” (often referred to as a soakaway but completely different in construction).

That is assuming permeability is acceptable, and a formal permeability test needs to be done. Then, if acceptable, a infiltration field can be designed accordingly. Permeability test requirements and infiltration field design and sizing criteria are all readily available online) Most merchants stock all the required materials and can advise accordingly. If the ground conditions fail the permeability test it will probably be advisable to consider replacing the septic tank with an appropriately sized package treatment plant, and discharge the clean water output to the adjacent watercourse as before. As this is not a ‘new’ installation planning permission will probably not be required, but it’s always advisable to contact the local council planning department to check. In all instances Building Regulations approval must be sought. It is vital to follow the guidelines provided in the “General Binding Rules” to ensure your clients are left with a fully compliant installation.

All the leading manufacturers of treatment plants can help, and supply installation guidance notes – basic building and groundwork skills are all that’s then needed for these works. Small plant, such as a 3 tonne mini excavator, and a small dumper, are usually all the plant needed to facilitate a typical installation.

Most builders and ground workers insurance covers excavation to max 3m deep. Most modern small scale sewage treatment plants are available in a “shallow”, version usually requiring a excavation of less than 2m deep, making them simple and safe to install with compact plant. Always ask the homeowner for details of incoming service positions, such as water, gas, telecomms, and electrics. Utilise a cable detection device and hand dig to ascertain the position of incoming services, and if unsure you can then position possible tank excavations and associated trench works to avoid these.

 

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