Mantair Instalation.

Specialists for all Septic Tank, Sewage Treatment Plant & Soakaway Problems

Septic Tank History

Septic tank systems ( also known as septic tank sewage treatment systems ) were first reported being used for serving the sewage disposal needs for properties in France around 1870. The septic tank invention is credited to Frenchman John Louis Mouras, who was able to patent the septic tank invention on 2nd September 1881. It is believed that the septic tank was first introduced to the UK in 1895.

Septic Tank Regulations

According to Part H2 of the 2000 Building Regulations, a septic tank should be sited at least 7 metres from any habitable parts of buildings. A septic tank should also be sited within 30 metres of a vehicle access, to allow emptying by a Licensed Waste Carrier and should be ventilated. Ventilation should be kept away from buildings.

A septic tank should have a capacity below the inlet of at least 2700 litres for up to 4 users. The tank size should be increased by 180 litres for each additional user.

Any owner of a septic tank is legally responsible to ensure that the tank does not cause pollution, a health hazard or a nuisance.

It is an offence under the Water Resources Act 1991 ( as amended by the Environment Act 1995 ) for septic tank effluent to be discharged into natural watercourses and renders the offender liable to prosecution by the Statutory Authorities, such as the Environment Agency or the local Council, depending on bylaws.

Septic Tank Types

Septic tank systems were historically made from traditional materials such as brick or concrete and comprised two rectangular chambers with dip pipes at the inlet and outlet of the septic tank, these were designed to prevent floating matter from passing through the tank.

A modern septic tank is normally made from GRP or Polyprothene and incorporates an internal baffle. This type of septic tank is most commonly spherical in shape with an access shaft leading to ground level.

Septic tank access covers should be of durable quality having regard to the corrosive nature of the septic tank content.

Septic Tank Process

A septic tank operates by using a process called ‘Anaerobic Digestion’ – a biological process promoted by the action of bacteria in the absence of dissolved oxygen. Inside a septic tank sewage solids settle to the floor of the tank whilst materials such as tissue or fat float to the top of the liquid level. The bacteria inside a septic tank help ‘digest’ the solids. The liquid in the septic tank then passes into a soakaway network, this liquid still contains about 70% of the polluting matter in the sewage. It is essential that the sewage is held in the septic tank long enough for decomposition to take place, if the septic tank is too small the resulting discharge will be even more polluting than normal and may even include “gross solids”. These solids can block the septic tank soakaway system.

A septic tank operating under normal use would require emptying annually. Failure to empty the septic tank when required, could again result in solids blocking the septic tank soakaway.

Septic Tank Effluent Soakaway

An effective soakaway for the septic tank effluent is critical to the effective performance of the system. The most commonly used form of septic tank soakaway is a sub-surface irrigation area comprising a herringbone pattern of land drains, laid in shingle filled trenches. The area of land and length of soakaway required must be to established by means of a percolation test.

If a septic tank soakaway is used where ground conditions are not suitable i.e. high water table or impermeable sub strata, then this may result in a high liquid level in the septic tank and in most cases flooding in the foul drains.

Septic Tank Advantages

A septic tank has relatively low capital costs with low maintenance requirements. A septic tank also does not require an electrical power supply.

Septic Tank Disadvantages

A septic tank can cause a smell nuisance and is totally reliant on the efficiency of the soakaway system. The effluent produced from a septic tank cannot be discharged to a ditch or stream.

Innovation in Septic Tank Design

There is now a move away from traditional septic tank systems with the Environment Agency preferring the installation of sewage treatment plants.

Septic tank conversion units are ‘retro fit’ units which can be installed within existing septic tanks. The Mantair conversion unit was first designed in 1984. Read more about septic tank conversion.