Foul Drainage Systems

We have installed many systems over the years and we have seen great advances in the treatment of foul waste in private systems.

No longer is there any concern when a property is beyond the main sewer – we have systems which will cope with all situations and can exceed Water Authority main sewers.

The Environmental Agency has played a large part in contolling pollution from old and outdated systems – further stringent controls were introduced in November 2019 which are detailed below. We believe Graf drainage systems provide the technical knowledge to ensure their plants will meet the requirements now and for the future.

Foul drainage systems – 4 main categories

• Mains Sewer – a network of sewers connected to a large sewage plant controlled by Local Authority or Water Authority. Each house has a separate connection in a town or village – rural properties seldom have a main sewer available.
• Cesspit – a tank below ground as a sealed vessel with no outlet. These tanks require emptying every 3/6 months by tanker and safely disposed to a recognised plant.
• Septic tank – series of chambers or a partitioned tank below ground to allow bacterial breakdown of waste to discharge effluent into ground via a drainage field with good porosity. Septic tanks should be emptied every 6 months or annually.
• Treatment plant – a partitioned tank below ground with chambers capable of allowing Aerobic and Anaerobic bacteria to break down solids using compressed air or slowly revolving discs – the resulting solution or effluent is relatively harmless and can be discharged to a drainage field or to a river or stream subject to controls by the Environmental Agency. Treatment plants should be emptied and serviced annually.

General Binding Rules

Whether the discharge is existing 31.12.2014 or new discharge 01.01.2105, the same rules apply below:

• Use the correct treatment plant – you must use a septic tank or treatment plant to treat the sewage and then discharge the effluent to ground via a drainage field. NB You cannot use a soakaway (designed for rainwater), well or borehole for discharging effluent to ground. Upgrading is required to a drainage field or apply for a permit to the Environmental Agency to assess the type of system required in your location.
• Your treatment plant must meet the right British Standard – the standards currently in force for new systems are: BS EN12566 for septic tanks and small sewage treatment plants BS 6297:2007 for drainage fields.
• Your treatment plant must be installed correctly and have enough capacity.
• Have your system regularly emptied and maintained.
• If you sell your property: tell the new owner about the sewage treatment system.
• If you stop using your treatment system; make sure it’s properly decommissioned.

Nutrient Neutrality (Nn)

Within our Solent Catchment area, there is a focus from Natural England to reduce levels of nitrates and potassium within coastal regions. High levels have been recorded which can cause algae growth within coastal waters. Graf have generated control systems within their plants to reduce the finished effluents to very low levels – they are leaders in this technology.

Septic Tanks

Septic tanks remain an option, but over time these units are likely to be phased out since they will not be able to provide acceptable levels of finished effluent.

• GRAF Septic tanks – Read more
• Surveys
• Design and approval
• Installation
• Drainage Fields
• Replacement House Drainage
• Re-instatement Works
• Commissioning
• Compliance Certificate
• Onward Maintenance

Rainwater Harvesting

• GRAF Rainwater Harvesting Systems – Read more
• Surveys
• Design system and management
• Installation
• Replacement system
• Storm Water Management
• Garden Water
• Re-instatement Works
• Commissioning
• Compliance Certificate
• Onward Maintenance