Frequently asked questions

Our expertise across the four divisions allows us to work across a both domestic and commercial projects from single dwellings to large scale housing developments and commercial contracts.

Our Consulting Engineers handle design, Environment Agency permitting, planning-related drainage assessments and expert witness work.

The WCI Nutrient Neutrality team produces NNAMS and sHRA reports for developers, sells council-approved phosphate credits, and operates the Free Upgrade Scheme for eligible homeowners in Somerset.

The team of Water & Wastewater Engineers deliver the full scope of installation and groundworks, from straightforward domestic septic tank replacements to complex commercial multi-system contracts.

Our Service Engineers carry out maintenance servicing, commissioning, emergency call-outs, compliance surveys and all forms of survey and testing for existing systems.

Four divisions, one point of contact with WCI Group.

WCI does not operate tanker emptying services directly, but we are happy to recommend trusted emptying contractors in your area.

The frequency with which a system needs emptying depends on its type, size and loading. Small domestic systems are typically emptied once every one to three years; commercial systems may need emptying every two to six months.

When WCI services your system, we take a sludge reading and measure ammonia values in the discharge, which allows us to advise precisely when emptying is required.

WCI is not affiliated with any single manufacturer. This means we always recommend the system that best meets the individual needs of the site and the client, rather than the one we are commercially incentivised to sell. We are accredited installers and service providers for a range of systems and have experience installing, commissioning and servicing all makes and models of water and sewage-related equipment, including GRAF, Marsh, WSc, Premiertech Aqua, Klargester, Tricel, Xylem and TT Pumps, among many others.

Yes. WCI carries professional indemnity insurance, contractors all risks insurance, and public, employers and products liability insurance. All staff are trained and qualified to the appropriate level for their roles. Our Civil Engineers hold relevant engineering degrees, our Project Engineers are fully qualified surveyors and site managers, and our Service Engineers are in-house trained and British Water accredited. Our Workmanship Warranty for installation services is available on request.

In our experience, the five most common compliance failures are:

A septic tank discharging directly into a ditch, watercourse or highway drain. Septic tanks must discharge to the ground via a drainage field.

A system that has failed due to a lack of maintenance – for example, a blocked or collapsed drainage field, damaged tankage, or ingress of rainwater into the system.

A tank that is significantly undersized for the current property, typically where bedrooms have been added without the foul drainage system being upgraded accordingly.

A system that requires a permit – for example, where discharge exceeds 2m³ per day to the ground, or the drainage field is within 50 metres of a private drinking water supply.

A system where the old septic tank has been replaced by a package sewage treatment plant, but the effluent was directed into plastic rainwater crates rather than a properly designed drainage field or watercourse – which is not a legal discharge point.

Yes – in principle. If you are purchasing a property without a mortgage, or you can satisfy your lender that the system will be brought into compliance within 12 months (the Environment Agency’s standard requirement), a sale can proceed. However, in practice, lenders will often refuse to lend on a property with a confirmed non-compliant system. If the sale does go ahead, the obligation to bring the system into compliance passes to you as the new owner. Most buyers in this situation negotiate a reduction on the purchase price to offset the cost of replacement. If you are involved in buying or selling a property with a private drainage system, contact us early – a compliance survey and a clear remediation plan can prevent delays and abortive costs.

Under Section 23 of the Land Drainage Act 1991, consent is required before piping, culverting or obstructing a watercourse – whether permanently or temporarily. This can include installing new headwalls or outfall pipes, and in some cases may apply to repairs and maintenance works.

Who you need consent from depends on the location and classification of the watercourse:

If the watercourse is a Main River, you will need Flood Defence Consent from the Environment Agency.

If the watercourse is within a Drainage Board area (for example, the Axe Brue, Parrett or North Somerset Levels in Somerset), consent must be obtained from the relevant Drainage Board. Note that any activity within 9 metres of a watercourse in these areas requires Drainage Board consent.

If the watercourse is an ordinary watercourse outside a Drainage Board area and is not a Main River, consent must be granted by the local council.

WCI can advise on the correct consenting route for your project and assist with applications.

No – not directly. However, where the only available discharge point is a watercourse that happens to flow through a pond, it may sometimes be possible to demonstrate to the Environment Agency that the treated water is carried through the pond quickly and does not stagnate. This is a technically complex argument and can be difficult to make successfully. Where possible, discharging directly into a watercourse leaving a pond is always preferable and will be the Environment Agency’s expectation. Contact us to discuss your specific site situation.

You are the legal operator of a private drainage system if you own the property that uses it – including where the system is shared with another property – or if your property deeds or tenancy agreement state that you are responsible for maintaining it.

Under the General Binding Rules, if a property is sold, the outgoing operator must provide the new operator with a written notice stating that a small sewage discharge is being carried out, along with a description of the wastewater system and its maintenance requirements. You are not legally required to prove compliance at the point of sale, though questions about compliance are increasingly common during conveyancing – often late in the process, which can cause delays. If you are selling a property with a private drainage system, we strongly recommend commissioning a compliance survey in advance so you can answer any questions promptly and with confidence.

A soakaway is a pit or crate-based structure used for the attenuation and gradual release of rainwater (surface water) into the ground. Soakaways were historically used to receive septic tank effluent, but this has not been legal since 2007 and should not be confused with a drainage field.

A drainage field (also called an infiltration system) is the legal method of discharging treated effluent from a septic tank or sewage treatment plant to the ground. It consists of parallel, gravel-filled trenches fitted with perforated pipes, through which the effluent slowly percolates into the surrounding soil. Drainage fields must be designed and installed in accordance with British Standard BS 6297 and the relevant Building Regulations.

No. Rainwater and surface water should never enter a septic tank or sewage treatment plant. These systems are designed to treat sewage only, and are sized accordingly. Rainwater entering the system will overwhelm the treatment process, carry settled solids and bacteria into the drainage field or watercourse, and block or destroy the drainage field over time. Building Regulations (Part H) require rainwater and surface water drainage to be kept completely separate from foul drainage. If you suspect rainwater is entering your system, contact us – identifying and eliminating this is one of the most common and important maintenance interventions we carry out.

Yes. WCI has over 40 years of experience delivering foul drainage solutions for a wide range of commercial and large domestic applications, including systems serving multiple dwellings, campsites, hotels, visitor centres, care homes and industrial complexes. For commercial projects, we provide a full service: design, value engineering, installation, Environment Agency permitting, Building Control sign-off and ongoing maintenance. Call us to discuss your project.

Yes. For clients who already have a groundwork team on site, or who have the skills and resources to complete the installation themselves, WCI can design the system, supply the required tankage and components, and commission the system once it has been installed. We can also be available to provide technical guidance during installation if required.

Typically, the existing septic tank is emptied, decommissioned, infilled with suitable compressible material and the surrounding area is levelled and reinstated. If the new sewage treatment plant must be installed in exactly the same location as the existing tank, the old system will be fully excavated and the spoil disposed of responsibly.

Yes. All tankage and components installed by WCI come with the relevant manufacturer’s product warranty. WCI also provides a Workmanship Warranty covering our installation services, which is available to view on request.

See the answer in the Servicing section above. In short, yes – but only a competent, British Water-accredited technician can lawfully carry out the work.

Yes. WCI works with several UKAS-accredited laboratories. Our service engineers can collect effluent samples and arrange for laboratory analysis to demonstrate that your system is meeting the conditions of its Environment Agency permit.

Yes. Under Building Regulations, a trial hole must be excavated alongside the percolation test to determine the depth of the seasonal groundwater table. This information is required to ensure any drainage field designed and installed at your property meets Building Regulations and the relevant British Standards.

A percolation test determines how quickly water drains through the soil on your land. This data is required to calculate whether a British Standard drainage field can be adequately designed and installed at your property. If the soil drains too slowly (common in heavy clay soils) or too quickly (common in sandy soils), a conventional drainage field may not be viable. A percolation test will confirm what options are available to you.

WCI can carry out a compliance survey and issue a formal report confirming whether your system meets the General Binding Rules or the conditions of its Environment Agency permit. Where defects or non-compliances are identified, the report will include a costed plan for repair or replacement. This survey is frequently requested during property sales and conveyancing.

Foul odours from a private drainage system are usually caused by one of the following: an underperforming system; poor ventilation of the drainage pipework; a dry water trap (flush your toilets and run your taps to refill them); a broken pipe or seal; or a failed air admittance valve. WCI can carry out a smell investigation using dye, CCTV and smoke testing to identify the source of the odour and recommend a remediation plan.

See the answer in the Servicing section above. In short, yes – but only a competent, British Water-accredited technician can lawfully carry out the work.

Yes. WCI works with several UKAS-accredited laboratories. Our service engineers can collect effluent samples and arrange for laboratory analysis to demonstrate that your system is meeting the conditions of its Environment Agency permit.

Yes. Under Building Regulations, a trial hole must be excavated alongside the percolation test to determine the depth of the seasonal groundwater table. This information is required to ensure any drainage field designed and installed at your property meets Building Regulations and the relevant British Standards.

A percolation test determines how quickly water drains through the soil on your land. This data is required to calculate whether a British Standard drainage field can be adequately designed and installed at your property. If the soil drains too slowly (common in heavy clay soils) or too quickly (common in sandy soils), a conventional drainage field may not be viable. A percolation test will confirm what options are available to you.

WCI can carry out a compliance survey and issue a formal report confirming whether your system meets the General Binding Rules or the conditions of its Environment Agency permit. Where defects or non-compliances are identified, the report will include a costed plan for repair or replacement. This survey is frequently requested during property sales and conveyancing.

Foul odours from a private drainage system are usually caused by one of the following: an underperforming system; poor ventilation of the drainage pipework; a dry water trap (flush your toilets and run your taps to refill them); a broken pipe or seal; or a failed air admittance valve. WCI can carry out a smell investigation using dye, CCTV and smoke testing to identify the source of the odour and recommend a remediation plan.

Nutrient neutrality catchment boundaries can be found on Defra’s Magic Maps application at magic.defra.gov.uk. The relevant map layers are: Designations > Land Based Designations > Statutory > Nutrient Neutrality Catchments. Alternatively, send us your site’s postcode and we will check for you.

If your site falls within a designated nutrient neutrality catchment, it is very likely that a NNAMS and sHRA will be required as a condition of submitting a planning application. These requirements vary by LPA, so always check with your local planning authority early in the project. You can also contact WCI with your site’s postcode and we will confirm whether it falls within an affected catchment.

A Shadow Habitats Regulations Assessment (sHRA) is a preliminary screening report that assesses whether a proposed development is likely to have a significant effect on a protected habitat site – typically a Special Area of Conservation (SAC), Special Protection Area (SPA) or Ramsar site. The report is submitted to the LPA, which uses it alongside its own Habitats Regulations Assessment. Like the NNAMS, it is frequently a validation requirement for planning applications in affected catchments.

A NNAMS is a Nutrient Neutrality Assessment and Mitigation Strategy. It is a technical report that calculates the nutrient load associated with a proposed development and sets out the measures – whether on-site or off-site – that will be used to achieve nutrient neutrality. Many Local Planning Authorities (LPAs) require a NNAMS as a validation document before they will accept and register a planning application.

Nutrient neutrality is a planning requirement, introduced in 2020, designed to ensure that new development does not increase the load of nitrogen and phosphorus entering sensitive water environments – particularly rivers, lakes and wetlands that are designated for their ecological importance. In simple terms, if a new development will generate nutrient pollution, the applicant must demonstrate that an equivalent or greater reduction in nutrients has been secured elsewhere before planning consent can be granted.

Option 1: Standard Terms – Most Common

• 10% non-refundable deposit upon credit reservation
• Up to 90% balance due on commencement

Minimal upfront exposure protects your project if planning is refused.

Deferred Payment – Large Outline Applications

• 10% non-refundable deposit upon credit reservation
• Balance payment deferred until Reserved Matters approval or closer to commencement

Designed for strategic allocations or outline permissions where construction commencement is years away. Improves cash flow management across long planning horizons.

Option 3: Upfront Payment

• Full payment upon credit reservation
• Potential discount for immediate settlement – discuss with WCI Nutrient Neutrality team

Suitable for funded developments seeking maximum cost certainty and potential pricing benefits.

Option 4: Bespoke Terms (Complex Developments)

• Custom payment structures for phased developments, land promotions, or unusual circumstances

Every project is different. Speak to our Nutrient Neutrality team to structure commercial terms that align with your specific planning and funding timeline.

Temporary phosphate offsetting for developments where permanent solution timing remains uncertain.

Useful for:

Outline permissions where construction timing is uncertain
Developments where on-site mitigation may become viable in future
Strategic allocations with long build-out programmes

WCI is uniquely positioned to deliver nutrient neutrality solutions. Our Consulting Engineers have produced more than 500 NNAMS reports and have a thorough understanding of development, planning and the regulatory environment. Our construction division has been installing sewage treatment plants for over 40 years. Our British Water-accredited Service Engineers are qualified to commission and maintain the treatment plants that generate our credits. And our balance sheet means we can deliver on our promises. We are a single source of expertise across the full nutrient neutrality process – from calculation to credit generation to monitoring.

Payment terms depend on how and when you purchase credits:

If you have secured your credits via a Reservation Notice prior to a planning decision, a 10% non-refundable deposit is due upfront, with the balance typically payable on planning approval. For large outline planning applications, payments are often deferred until closer to commencement.

If you purchase credits after planning approval has been granted, full payment is due on agreement of the purchase.

Please refer to the contract issued at the time of purchase for full payment terms.

Yes. WCI has bridging credits available across all of the catchments in which we operate. Contact our Nutrient Neutrality team to discuss eligibility and availability for your development.

Bridging credits are temporary phosphate credits that can be used to cover the difference between a development’s phosphate balance immediately after planning and its expected long-term balance. They are a tool to allow development to proceed while permanent mitigation is being put in place.

WCI’s Free Upgrade Scheme offers eligible homeowners in Somerset a completely free replacement of their existing septic tank with a modern, fully compliant Graf sewage treatment plant. There is no cost to the homeowner for the installation. The scheme is funded by developers who need to purchase phosphate credits to satisfy nutrient neutrality planning conditions in the Somerset Levels and Moors catchment area. When WCI installs a new sewage treatment plant and decommissions the old septic tank, the improvement in wastewater treatment quality generates the phosphate credits that developers need.

Yes – there is no charge to the homeowner for the installation of the new sewage treatment plant. The scheme covers the full cost of supply, installation and decommissioning of the old system. Please note that the scheme does not cover additional drainage work that may be required outside of the core installation scope – for example, removing rainwater connections from the foul drain, replacing damaged pipework upstream of the tank, or remedying failed drainage fields. If a site survey reveals that additional work is needed before installation can proceed, we will advise you and provide a separate quote for that work.

The scheme is funded by developers who require phosphate credits to satisfy nutrient neutrality conditions attached to their planning consents within the Somerset Levels and Moors Ramsar catchment. When WCI upgrades a septic tank to a sewage treatment plant, the measurable reduction in phosphorus loading generates phosphate credits that can then be allocated to a developer’s planning mitigation. The homeowner pays nothing because the developer purchasing the credits is effectively covering the cost of the upgrade.

WCI has over 40 years of established presence in Somerset’s water and wastewater sector. We install, service, and maintain thousands of systems across the region. Our Managing Director, Brad Taylor, pioneered this upgrade credit model – an innovation now replicated nationwide. We are here for the long term.

To qualify for the scheme, you must: own a residential property with an existing septic tank; be located within an eligible catchment area in Somerset; and be willing to enter into a legal agreement with the Council committing to the ongoing maintenance of the new system. The scheme currently applies only to residential properties – it does not cover businesses, village halls, church halls or other non-residential uses, though residential properties with some commercial use (such as residential care homes) may be considered on a case-by-case basis.

Because the eligible areas do not neatly follow postcode boundaries, the simplest way to find out if your property qualifies is to register your interest and we will check your location using our mapping system.

Eligible areas do not follow postcode boundaries neatly. The quickest way to check is to register your interest – we’ll confirm your location using our mapping system advised by Natural England. There is no obligation at this stage.

Shared systems can be upgraded. However, all owners whose properties feed into the shared tank must register and agree to proceed – we cannot advance the upgrade for one property if another owner declines. If you wish to separate your drainage from your neighbour’s, this may be possible where a technically suitable separate discharge point exists, and we will assess this during the site survey.

Please speak to your neighbours before contacting us – we are not able to negotiate with them on your behalf.

Most installations take between three and five working days. Here is what to expect:

Day 1: The installation team arrives, establishes site setup, and delivers equipment

Days 2–4: Excavation, tank installation, pipework connections, and electrical hookup

Day 5: Final connections, commissioning, testing, and handover

You do not need to be home throughout. We bring portable toilet facilities so you’re never without access. Working areas are controlled to minimise disruption, and excavated areas are restored to a level finish on completion.

We ask that you minimise heavy water usage – such as running multiple laundry loads – for approximately 48 hours while the system is being connected.

Typically, the existing septic tank is emptied, decommissioned, infilled with suitable compressible material and the surrounding area is levelled and reinstated. If the new sewage treatment plant must be installed in exactly the same location as the existing tank, the old system will be fully excavated and the spoil disposed of responsibly.

Once complete, the only visible above-ground element is a small compressor housing – similar in appearance to a ventilation unit – positioned near a wall, hedge, or outbuilding. You will also see one or two new inspection covers at ground level. The installation area will be left level and tidy.

WCI does not re-landscape, re-seed, or re-turf gardens following installation under the scheme – you will need to finish the garden to your own preference or request this as a quoted job.

In almost every case, you will continue to have full use of your foul drains throughout the installation. We provide portable toilet facilities on site as an additional measure.

WCI installs Graf sewage treatment plants under the free upgrade scheme. Graf is a German manufacturer and their treatment plants are approved by Natural England for use in nutrient neutral areas under this type of scheme. The system is sized according to your property and in line with current Building Regulations.

Yes. The tank body carries a 15-year manufacturer’s warranty, and the serviceable mechanical components are covered for 2 years.

Warranty remains valid as long as annual servicing is maintained – another important reason to keep up with the service schedule.

Yes. WCI supplies and installs the new system at no cost to you, but ownership transfers to you on completion of the works. The system is yours in the same way your boiler or your roof is yours – it will need routine maintenance over its operational life.

The performance difference is dramatic:

• Old septic tank: typically discharges 1.5–2.5 kg of phosphate annually

• Modern treatment plant: discharges less than 0.1 kg of phosphate annually – a reduction of over 95%

Beyond phosphates, modern treatment plants are simply more effective across the board: better treatment of all pollutants, more reliable operation, better handling of variable loads, and full compliance with current environmental standards.

WCI produces a Technical Mitigation Report (TMR) demonstrating the phosphate reduction for council approval – this proves the environmental benefit is real and measurable.

When you proceed with installation, you will sign a document called a Unilateral Undertaking. The name sounds daunting, but it is simply a formal agreement with Somerset Council that confirms:

• You will maintain the upgraded system in good working order

• You will allow annual discharge monitoring (WCI carries this out free of charge for the first five years)

• You will only replace the system with one offering equivalent or better treatment

• You will allow the Council access on 21 days’ notice to inspect the system

• These obligations transfer to future owners if you sell the property

The agreement is registered with the council and runs with the land – meaning any future owner of your property will inherit the same obligations.

In practice, it simply means keeping up with the standard maintenance any treatment plant requires: annual servicing and periodic desludging every two to three years. Nothing unusual or burdensome.

Failure to maintain constitutes a breach of covenant, which the council can enforce. In practice, problems are rare – proper maintenance is straightforward and the annual service is quick and routine.

Yes – at any point before signing the Unilateral Undertaking, and with no financial charge. Once signed, you are committed for the system’s design life. However, if you later sell the property, the obligations simply transfer to the new owner and we update our records accordingly.

There are three main running costs to factor in:

Electricity – the Graf sewage treatment plant is highly efficient. For an average domestic property, electricity consumption is less than that of a 60-watt lightbulb, equating to approximately £65 per year.

Emptying – the tank will need to be emptied on average every two to three years. You can arrange this with any approved tanker operator.

Annual servicing – under the General Binding Rules, sewage treatment plants must be serviced annually by a competent person. The cost is approximately £150 + VAT per year and will rise in line with inflation. WCI covers the cost of discharge monitoring for the first five years following installation under the scheme.

Yes. Under the Environment Agency’s General Binding Rules, all sewage treatment plants – whether installed through our scheme or purchased privately – must be serviced annually by a competent person. Think of it like an MOT for your car: essential maintenance that keeps everything working safely and legally. This obligation exists for any treatment plant owner under current environmental law.

Yes – you are free to use any approved contractor for annual inspections and maintenance. WCI Service Engineers offer this service (and know the systems inside out, having installed them), but your choice of provider is never required and is entirely yours.

The survey, equipment, and installation are entirely free. However, a small number of situations involve additional costs that the scheme does not cover:

Solicitor fees

Most homeowners proceed without needing a solicitor. However, if your mortgage lender requires you to instruct one regarding the Unilateral Undertaking, any legal fees are between you, your solicitor, and your lender. WCI does not require you to use a solicitor.

Pre-existing drainage problems

If your current foul drainage has a fault that requires repair before the new system can connect – such as cracked pipes or collapsed drains – you would need to arrange and fund that repair separately. Our site survey identifies any such issues upfront, so there are no surprises.

Rainwater diversion

Many older septic tanks incorrectly receive rainwater from roof gutters mixed with foul water. Current regulations require these to be separated. If your existing guttering discharges into your septic tank, you will need to arrange diversion to a suitable soakaway before installation begins. This is usually straightforward groundwork.

Third-party land access

If installation requires crossing a neighbour’s land beyond our standard access agreement, any additional costs or arrangements are between you and that landowner. We always discuss foreseeable requirements during the survey.

The upgraded system and its maintenance obligations transfer to the new owner on sale – we simply update our records. This does not negatively affect your property’s value or saleability. You are transferring a modern, compliant wastewater system, which most buyers view positively, particularly in areas where septic tank replacement costs are a concern for purchasers.

Your solicitor will disclose the Unilateral Undertaking during conveyancing. If you let us know ahead of sale, we will update our records with the new owner’s details.

Mention this during the survey. We can design system capacity to accommodate planned extensions, ensuring your upgraded system won’t limit future development. If extensions arise after installation, contact us – many systems have spare capacity, or modifications may be possible.

Does the upgrade affect my council tax?

The Free Upgrade Scheme is not designed to respond to urgent or emergency situations. Funding for the scheme is directly linked to developer activity in the Somerset Levels and Moors catchment, and current market conditions – combined with a policy change allowing developers to receive planning consent without first securing a Reservation Notice – have significantly slowed the release of upgrade funding. A substantial wait is currently expected for scheme upgrades.

If your current system is failing and you cannot wait, WCI can still help – we have over 40 years of experience in off-mains drainage and can carry out a fast, fully funded paid installation outside of the free upgrade scheme. Contact us to discuss your options.

WCI Service Engineers can help keep your existing system functioning reliably in the meantime:

• Routine servicing to prevent breakdowns

• Compliance surveys if required for property transactions

• Smell investigations if you’re experiencing odour issues

• Rectification work for ageing systems in need of repair

Or, if you’d prefer not to wait, WCI Project Engineers can quote a paid installation with no waitlist – contact us on 01984 623 404.

No. If you decide not to proceed with an upgrade, or if your property does not qualify for the scheme, your details will not be shared with any third party. All personal data is held securely in line with our privacy policy.

Every system has emergency contact details displayed on the kiosk for urgent issues. For routine questions or service scheduling, contact WCI Service Engineers: 01984 623 404.