Septic Tanks

 Septic Tanks and Subsequent Drainage

About 800,000 septic tank systems operate in England and Wales. The design of the septic tank and its subsequent drainage is critical in ensuring the efficient working of the system. Approved Document H2 of the Building Regulations sets out the minimum requirements to be followed.

Here are some points to consider:

The Septic Tank

When installing a new septic tank always allow for future extensions to the property. Don't choose the minimum permissible capacity it may not be cost effective.

Septic tanks can be constructed on-site using brickwork or concrete but factory made units manufactured from glass reinforced plastics etc. are the norm. Ideally only tanks possessing a British Board of Agreement (BBA) Certificate should be installed and the leading manufacturers have this certificate.

The siting of septic tanks is important. They should be accessible for future maintenance or emptying and ideally not nearer than 15 metres to a dwelling.

Just as you would take advice from a Structural Engineer or Architect, you should consider taking technical advice from Environmental Engineering Consultants.

Subsequent Drainage

Effluent from a septic tank is usually disposed of by soakage into the ground provided that the disposal does not generate a pollution risk to surface waters or groundwater resources.

The most commonly used form of soakaway is a sub-surface irrigation area comprising a herringbone pattern of land drains laid in shallow shingle filled trenches.

The area of land required for the soakaway system has to be established by means of a percolation test. It is recommended that this test is conducted by an independent professional who is able to provide a certificate stating that the ground it suitable and that the test has been done satisfactorily.

TAKE CARE WHEN MAKING THE TEST TO AVOID ABNORMAL WEATHER CONDITIONS SUCH AS HEAVY RAIN, SEVERE FROST OR DROUGHT

Before effluent can be disposed of by soaking into the ground the consent of the Environment Agency will be required under the provision of the Water Resources Act 1991...see Useful Addresses below.

Useful Addresses and Contact Numbers

Environment Agency Regional Offices

North West

Richard Fairclough House
Knutsford Road
Warrington
Cheshire
WA4 1HG

Tel 01925 653999
Fax 01925 415961

Welsh

Rivers House
St Mellons Business Park
St Mellons
Cardiff
CF3 0LT

Tel 01222 770088
Fax 01222 798555

For Building Regulations Advice

Chester City Council
Building Consultancy
The Forum
Chester
CH1 2HS

Tel 01233 402224
Fax 01244 321876

Manufacturers of GRP septic tanks include...

Klargester Environmental Engineering Limited
College Road
Aston Clinton
Aylesbury
Buckinghamshire
HP22 5EW

Tel 01296 633000
Fax01296 633001

Entec
(Pollution Control)
West Portway
Andover
Hampshire
SP10 ELF

Tel 01264 353222
Fax 01264 366446

HELPFUL READING

Septic Tank Systems: A Users Guide: CIRIA

Code of Practice for the Design of Small Sewage Treatment Works and Cesspools BS6297:1983

Septic Tanks and Small Treatment Works: A Guide to Current Practice and Common Problems: 1993 CIRIA Technical Note 146

If you would like to speak to a member of the Building Consultancy Team please contact us, details below.

Contact Details

Building Consultancy

Email - buildingconsultancy@chester.gov.uk

Opening hours - 8.45am - 4.45pm

Phone number - 01244 402224

Fax - 01244 321876

Address - Building Consultancy, Development Directorate, Chester City Council, The Forum, Chester, CH1 2HS