Septic Tanks and Soakaways
These are generally found in rural areas where there is sufficient garden to install a private drainage system. Septic tanks are sealed units, either constructed using concrete blocks with a waterproof render finish or the GRP onion type.
The tanks are designed to be always full with a high level inlet and a high level outlet. When the raw sewage discharges into the septic tank the same volume is displaced out of the outlet and into the soakaway. The soakaway element is notorious for failing and, to ensure the longevity of the soakaway, the septic tank must be designed to have the correct hydraulic volume for the size of the property. The British Water Flows and Loads should be used for sizing septic tanks. The soakaway should also be sized using the infiltration testing methodology BS 6297.
Environmental Permits and do you need one?
Check to see whether the septic tank should be registered with the Environment Agency here.
How do you know your system is operating and is legally compliant?
If you are thinking about purchasing a property which has a septic tank it is strongly recommended that you obtain a Pre-purchase Home Owners Survey Report
NB It is strictly forbidden to discharge septic tank effluent directly into a watercourse
The septic tank should be de-sludged every 12 months.
If you are replacing an existing system, this will also need approval from your local Building Control office.