To get a effective soak away you must have good soil. If the subsoil is well drained along with well oxygenated (has a supply of oxygen) then it will typically be a reddish, brown or yellow shade. The most effective subsoil consists of chalk, gravel, sand, clay loam and sandy loam, whereas silty clay, clay and sandy clay are certainly not very good for percolation. Please note that the first place to look should be with the Environment Agency and the local authorities to find out if your land will be eligible for a soak away system. In case your entreaties to get a septic tank as well as soak away system is denied then you will need to install a cesspool.
To begin the percolation analysis you should dig a hole at least one meter squared and 2 meters deep, or one and a half meters under the invert of where you wish the drainage field to be. It is worthy of acknowledging that you must take into consideration the likely groundwater levels in the winter and in the summer to obtain the most accurate test. This may requires a test in both seasons.
Inside the hole previously dug, dig another hole 300mm cubed, and remove any free debris. You should then fill the 300mm square hole with water and let it drain naturally over night. Day after today you should refill the test hole, however now you need to see how long it takes, in seconds, to seep away. Record final results from 75% full to 25 percent full. For example the depth at 225mm, then 150mm and at last at 75mm. You need to then divide the answer by 150, this will provide the average time it takes in seconds for the fluids level to drop 1mm. To find the most accurate results you should carry the test out no less than three times, with at least two unique trial holes. Take note that you should not carry the test out when it is raining heavy, when you have a drastic drought or frost.
You should only install a soak away when the experiment implies that the average outcome for the liquid to drain away is between twelve and one hundred. In case your test results are outside of these limits then soak away isn t likely to be affective. Nonetheless this could be overcome should you have an alternatively 2nd treatment for the sewage effluent.
To calculate the dimensions of the soak away you require you should use the following equation -
The area in meters squared = [the typical time in seconds for your water to drop by one mm in the test hole (V) x the maximum number of people that the septic tank is designed for (p)] x 0.25 for septic tanks (in case you have a sewage treatment plant then times the amount by 0.20) Please note you should first times V by p before times the result by either 0.25 or 0.20
Easier mathematical arrangement -
Septic tank area = Vp x 0.25
Sewage treatment plant = Vp x 0.20
