To have a good soak away you must have good soil.  When the subsoil is well drained and well oxygenated (has a supply of oxygen) then it will typically be a reddish, brown or yellow color.  The best subsoil is made out of chalk, gravel, sand, clay loam and sandy loam, whereas silty clay, clay and sandy clay are not very good for percolation.    Take note that the first place to look should be with the Environment Agency as well as the local authorities to find out if your land will be eligible for a soak away system.  If you application for a septic tank as well as soak away system is denied then you will need to install a cesspool.

To begin the percolation test you should dig a hole at least one meter squared and two meters deep, or one and a half meters below the invert of where you want the drainage field to be.  It is worth noting you should take into consideration the likely groundwater levels in the winter and in the summertime to get the most legitimate test.  This might requires a test in both seasons.

Within the hole already dug, dig an additional hole 300mm cubed, and take out any loose debris.  You should then fill the 300mm square hole with water and permit it drain naturally over night.  The following day you should refill the test hole, however this time you should see how long it takes, in seconds, to seep away.  Record the outcomes from 75% full to 25 percent full.  For example the depth at 225mm, then 150mm and finally at 75mm.    You need to then divide the answer by 150, it will give you the average time it takes in seconds for the water level to drop 1mm.  To find the most accurate results you should carry the test out a minimum of three times, with at least two different trial holes. Take note that you should never take the test out when it is raining heavy, when you have a drastic drought or frost.

It is best to only install a soak away when the test implies that the typical outcome for the liquid to drain away is within twelve and one hundred.  Should your test results are beyond these limits then soak away isn t likely to be efficient.  Having said that this could be overcome if you have an alternatively 2nd treatment for the sewage effluent.

To calculate the dimensions of the soak away you require you should use the subsequent 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 individuals that the septic tank is made 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 that you should first times V by p before times the outcome by either 0.25 or 0.20

Septic tank area = Vp x 0.25

Sewage treatment plant = Vp x 0.20