Burford Concrete Tanks have developed a Dosing Septic Tank
that is suitable for effluent-dosing to soil absorption systems.
Suitability
The Burford Dosing Septic Tank has a built-in dosing chamber (second septic chamber) equipped with a shallow-draught automatic dosing siphon.The effluent distribution pipe in the infiltration trench or bed must be 500 mm or more lower than the sewer into the septic tank.
Examples include deep infiltration trenches/beds on level sites and shallow trench systems that are down-slope of the septic tank on hill sites.
The dosing siphon is made of PVC plastic and has no moving parts.
It operates automatically, with discharge starting when water in the dosing chamber reaches the 'trip' level, and stopping when discharge has brought the water level down to 160 mm below the trip level (corresponding to a dose volume of approximately 220 litres).
System Design requirements for using the Burford Dosing Septic tank
Effluent distribution pipes should be designed to discharge at a flow rate between 60 litres/minute and 180 litres/minute.The standard dose volume is approximately 220 litres.
For a Burford Dosing Septic Tank buried with the top of the tank 300 mm below ground level, the invert of the outlet from the tank will be 1000 mm below ground level.
Effluent distribution pipes in soil absorption systems can be of two basic types:
- Large diameter (100 mm) pipes with large (10 mm diameter) discharge holes
- Small diameter (32-40 mm) pipes with small (3-4 mm diameter) discharge holes
This type of distribution pipe is flooded during dosing and requires only minimal water pressure in the pipe (less than 100 mm).
Soil absorption systems using this type of distribution pipe require a 1:100 grade on the 100 mm DWV conveyance pipe from the dosing tank to distribution pipe(s) of the soil absorption system.
The distribution pipe(s) can be as little as 100mm lower than the outlet from the siphon dosing tank.
For soil absorption systems using the smaller type of distribution pipe (called Low Pressure Pipe) there should be a minimum of 1000 mm water pressure in the distribution pipe(s) during discharge, implying a similar amount of fall from the dosing tank outlet to the soil absorption system.
Examples of such systems are cross-slope sand filter-mounds and shallow contour-trenches located down hill from the dosing tank.
Customised Dosing Siphons
The 160 mm draw-down is for the standard siphon.Siphons can be adjusted in the factory for draw-downs up to 185 mm, if required, thereby increasing the dose volume by up to 15%.
Paired siphons can be installed in the dosing chamber for automatic alternating dosing to two effluent distribution systems.
Maintenance
The dosing siphon should not require cleaning or maintenance.However, if a blockage should occur, the top of the siphon 'bell' is removable and all parts of the siphon can be cleaned.
For more detail, contact us directly for customised advice.
Tagwords: dosing, septic tanks
