How To Do A Percolation Test (Soakaway Size Calculator)
21 Aug 2021
The purpose of a percolation test is to see how long a length of field drain (soakaway) you need for your Sewage Treatment Plant. One might also call it a soakaway size calculator. See this document for more information. You'll need to record your results here.
Step 1: Dig
Excavate at least three holes 300mm square to a depth at least 300mm below the proposed invert level (300mm) of the infiltration pipe, spacing them along the proposed line of drainage.
If the water table is reached, please note at what depth.
Step 2: Fill
Fill with water to 300mm and allow to seep away completely. If the water drains rapidly (within 10 mins), then the hole should be filled again up to a maximum of 10 times.
Is It Suitable?
If the water continues to drain away rapidly, then the ground is not suitable.
Also if the water has not soaked away within 6 hours, the area is not suitable in this case either.
We will calculate the length of drains needed. We will need the number of dwellings involved and the number of bedrooms.
Record the results on this chart:
Here is an example of a completed form: