What is a percolation test used for?
A percolation test is a requirement needed before you can install a new soakaway system or make changes to an existing soakaway. It helps you to determine the amount of time it takes for water to soak into your soil.
Do I need to do a percolation test?
If you are thinking of adding a soakaway system or replacing an old soakaway you will need to check the suitability of your ground beforehand. Some soil types are not suitable for soakaway systems.
Can I do my own percolation test?
Best to check with your local council, depending on your area and size of soakaway you may need a company registered with the council to perform the test for you. Otherwise, your good to go yourself.
Is a percolation test mandatory?
It is an important test if you want your soakaway to be successful. In some areas it is a requirement of adding a soakaway system.
What does a percolation test for?
A percolation test measures how long it takes an amount of water to drain from a set area. This will allow you to measure the suitability for drainage.
Please note If you want to install a septic tank or other dispersal systems you will additionally need to test for suitability.
How do I perform a percolation test?
- Dig 2 test holes within your proposed soakaway area.
- Dig the holes 300mm square
- Dig the holes below the planned level of the crate /outlet pipe 300mm
- Fill the hole with water to 300mm
- Time how long the water takes to drain. If the water does not drain, then your soil type is unsuitable for a soakaway system.
- When the water in the test hole is ¾ full, time how long it takes until the water has drained away to ¼ full.
- This time measurement will help you work out the Vp number.
- Repeat test at least 3 times and average your results for both test holes.
- First multiply your average time by 60
- Then divide your answer 150 (the amount the water has gone down) to give you the time it takes for the water to disperse.
- If your result is between 15-100 you have a perfect soakaway situation. Your ground will provide a slow and steady soakaway solution.
How are percolation test results calculated? – Vp
Example
45 minutes to reduce from ¾ to ¼ in the test hole. (Average over at least 3 tests in 2 test sites)
45×60=2700
2700/150 = 18
Vp – 18
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