Purchasing a home in the UK that utilises a private septic tank system requires some extra due diligence around legal obligations, expenses, maintenance, and environmental impact compared to properties on main sewer lines.
This extensive guide by our team at ADP Enviro aims to clearly explain considerations around septic tanks to allow buyers to make well-informed decisions.
What Exactly is a Septic Tank System?
So, how does a septic tank work? A septic tank in-house system treats and disposes of wastewater and sewage without connections to main sewage lines. The key components include:
- Septic Tank – Buried, watertight tank that receives all household wastewater and separates solids from liquids. These concrete, steel, or fibreglass tanks range from 1000-1800 gallons for typical households.
A series of baffles allows heavier sediments to settle to the bottom forming sludge while lighter greases and fats float to the top as scum.
- Drainage Field – Network of perforated pipes (about 13mm in diameter) dispersing liquid effluent from the septic tank into permeable shallow soil trenches for further treatment. Also called a leach field or absorption bed. The size depends on the system capacity needed.
A typical drainage field may contain over 40 metres of buried filter piping. Older houses may have just a single drainage pit rather than piped drainage fields.
- Soil Absorption System – The soil and biome processes that remove contaminants, nutrients, bacteria, and viruses from the effluent as it permeates through the absorption trench.
Cation exchange and filtration occurs along with microbiological processes. Proper soil structure, porosity, and properties play a key role in these natural treatment processes.
- Vent Pipes – Release sewer gases produced by the anaerobic biological breakdown of waste within the sealed septic tank. These vent pipes extend above the roof line to safely disperse methane, hydrogen sulphide, and other gases while preventing pressure build up.
General Binding Rules for Homeowners
In 2015, General Binding Rules for septic tanks came into effect, enforcing strict regulations on septic tank systems to protect water quality under EU and UK statutes. Key rules include:
- Tanks in sensitive groundwater areas must have secondary effluent treatment using systems like package sewage treatment plants that disinfect bacteria and reduce biochemical oxygen demand before discharge into drainage fields. Older septic tanks may require upgrades to meet environmental standards.
- Effluent discharged from the tank to drainage fields must meet quality standards for solids, organics, nutrients, and dissolved oxygen or additional stages of treatment may be mandated. Regular effluent testing may apply in some regions.
- Drainage fields cannot be located near buildings, watercourses, or groundwater sources designated for human consumption. Mandated buffer zones apply between drainage fields, ponds, wells etc. Access for inspections and maintenance must be ensured. Any decommissioned cesspits on the property will also need approval.
- Local authorities require regular inspections based on risk ratings. Upkeep logs should be maintained by homeowners including sludge depth, maintenance contracts, pumping schedules, inspection reports and any compliance certificates.
Septic Tank Installations and Planning Permission For Homeowners
New septic tank installations require approval to ensure compliance with building regulations for drainage fields, soil percolation, system capacity calculations, and environmental obligations.
Applications require detailed project documents with maps, technical specifications, construction plans, and environmental impact assessments.
Homebuyers may need planning permission before upgrading outdated or non-compliant systems. In some cases where existing systems have caused pollution, property buyers may be legally responsible for remediation costs.
Carefully review all permissions and compliance documentation with professionals when purchasing a home, taking nothing for granted.
Homebuyer Checklist: Key Septic Tank Questions
Prospective buyers should thoroughly investigate the property’s septic tank including:
- Age, Type and Design: Request detailed schematics. What materials and drainage system design were used? Check for fibreglass, concrete, metal, or plastic construction. How old are key components? Newer advanced systems with multiple integrated tanks, syphons, pumps, alarms and tertiary treatment may be more efficient whereas older overflow systems can contaminate groundwater and necessitate upgrades.
- Condition and Capacity: Inspection reports will detail current state of tank, absorption trenches, pumps, seals etc along with the hydraulic capacity matched to property size, projected flows based on occupancy, and headroom for future expansions. What is the estimated remaining lifespan? Recent upgrades completed?
- Maintenance History: Review accessible detailed records of past pumpings, repairs, issues detected, solutions implemented and compliance inspections. Are there guarantees or warranties in place? Has a regular maintenance contract been maintained?
- Regulation Compliance: Confirm current adherence to General Binding Rules around drainage field placement and buffers, effluent standards, groundwater separation distances and required upgrades. Is the system registered? Request copies of all compliance certificates.
- Location considerations: Impact on property planning permission for extensions, patios, driveways or drainage modifications? How might renovations affect the buried system locations? Are accessible covers provided to all system access points?
Understanding Septic Tank Expenses
- Inspection Costs: £150+ for detailed written condition reports performed by specialists. Additional costs for percolation tests, system diagnostics, effluent sampling and environmental surveys.
- Emptying/Pumping: £200-300 every 3-5 years depending on tank size and household occupancy. Additional fees for emergency blockage clearing, removal of difficult sludge consistencies, and contaminated waste disposal.
- Maintenance: Annual costs around £100+ for inspections, upkeep, repairs of pumps, seals, alarms, ventilation and minor part replacements. Ongoing costs for water quality and groundwater testing may also apply.
- Installation: £5000+ depending on complexity, soil factors, site access and system type. Total costs for drainage field excavation and installation, connecting pipework, electrical controls, permitting paperwork and final site restoration.
- Upgrades/Repairs: £2000+ for drainfield restoration involving soil replacement, drainage modifications, re-leveling and reseeding. High costs for full tank replacement, upgrades to treatment plants, electrical pumps and integrated control panels.
Professional Pre-Purchase Septic Tank Inspections
Before completing purchase, it is highly advisable for both the home seller and prospective buyer to independently commission septic tank inspections from qualified wastewater professionals.
Seller’s Compliance Surveys
UK home sellers should arrange an invasive compliance survey as early in the sales process as possible.
This audit will reveal if the existing septic tank arrangement adheres fully to current General Binding Rules around location, capacity, construction standards and environmental obligations.
Following your home sellers compliance survey, any remediation requirements or upgrades to achieve compliance can then be completed ahead of property listings. Sellers should disclose any major works undertaken.
Buyer’s Pre-Purchase System Checks
In turn, home buyers should arrange a thorough examination by an independent specialist prior to sale completion.
This inspection probes beyond visible components to identify leaks, cracks, root intrusion, tank corrosion and other deficiencies. Expert home buyer septic tank surveys also entail water flow gauges, drain camera scoping, soil percolation tests and remaining lifespan estimates.
The buyer’s compliance check both protects their interests prior to property purchase while allowing negotiations on price, required repairs or system replacements.
Identifying major undersized or failed systems early can prevent a painful post-purchase crisis. Seeking specialist second-opinions, beyond basic visual checks, provides home buyers total confidence during a stressful purchase.
Still Unsure? Contact ADP Today
With extensive expertise in all aspects of septic system maintenance, ADP Enviro are the UK leaders in septic tank compliance surveys, installation, upgrade works and wastewater consultancy.
Our professional team can deliver complete septic inspections with detailed condition reports and remedial advice so both buyers and sellers can gain full confidence in their transactions.
Contact ADP Enviro today for further advice and assistance.
