Choosing/building a suitable septic tank
There are several key properties that your septic tank requires to be legally compliant and satisfy health and safety regulations.
- Any factory-made septic tanks should meet the British Standard EN 12566-1.
- If you have constructed your septic tank out of brickwork or concrete, ensure that it is roofed with heavy concrete slabs. Bricks used in the walls of the tank must be an engineering brick model that is at least 220 mm thick. Mortar used must be a 1:3 cement-sand ratio. In-situ concrete should be at least 150 mm thick.
- The septic tank must have ventilation and this should be installed such that there is no leakage of the contents and the ventilation is kept from buildings.
- The capacity below the level of the inlet of the septic tank should be 2,700 liters for up to 4 users then an additional for 180 liters for each user above that.
- Ideally, there should be two chambers within the tank that operate in series and prevent immediate disturbance upon the entry of new waste through the inlet.
- If the septic tank has a width of 1.2 metres or less then the inlet must be a dip pipe.
- Steeply laid drains should limit velocity of incoming waste by laying the last 12 metres at a gradient of 1/50 or flatter to prevent turbulence.
Required marking of your septic tank
- Nearby habitation must have a notice regarding the septic tank affixed to a wall.
- The notice must state that the septic tank is in use for foul drainage discharges, the type of secondary treatment used, the maintenance required and that the owner is legally responsible the system does not cause nuisance, pollution or a health hazard.
Choosing where to place your septic tank
- Ensure that your septic tank is at least 7 metres from any habitable sections of buildings.
- If possible, place the septic tank downslope from any habitation.
- Place the septic tank in a position such that it is within range of a hose such that the tank can be cleaned and emptied but does not endanger any occupants of nearby buildings.
- The septic tank should be no more than 30 metres from any vehicle access point (to allow access for a tanker to take and remove the waste.
- Ensure that the invert level of the tank is a maximum of 3 metres below the level of vehicle access.
Maintenance of your septic tank
- The septic tank must be emptied at least once every 12 months by a licensed contractor.
- An inspection must be carried out monthly of the outlet chamber or the distribution box to observe the effluent is free-flowing and clear.
- The septic tank must be used in conjunction with a secondary treatment such as a drainage field, drainage mound or a constructed wetland & this will have its own maintenance procedure.