How To Size A Soakaway For A Septic Tank Or Sewage Treatment Plant
If you are installing a septic tank and some times a sewage treatment plant you will have to also construct a soakaway for the waste water to discharge to.
Fill the 300mm square hole to at least the 300mm mark and allow to soakaway over night.
On the next day, fill to the 300mm mark again and observe the time it takes to soakaway in seconds, from 70% full to 25% full.
Divide the time taken by 150. The answer gives you the average time in seconds (V).
Carry out this test at least 3 times in at least 2 different places.
How to Perform the Percolation Test Calculations:
Pipes should be laid on a 300mm layer of shingle or medium of up to 50mm.
The trenches must be filled 50mm above perforated pipe and covered with a membrane and then filled in with soil.
The trenches for the soakaway should be between 300mm and 900mm wide with a distance of 2m between trenches.