Soil infiltration
Timed observations indicate whether water moves through the ground at a suitable rate.
Percolation testing
Measure how water moves through the soil
On-site testing to help assess ground suitability and inform the design of a drainage field or infiltration system.
What a percolation test helps establish
The results provide evidence about how quickly water drains through the soil at the proposed location.
Drainage-field sizing
The measured percolation value forms part of the calculation used to establish the required infiltration area.
Early design confidence
Testing can identify unsuitable conditions before a proposed drainage layout is taken further.
A controlled test carried out on site
The precise method and number of test locations depend on the proposed drainage arrangement and site conditions.
Review the proposal
Confirm the property, proposed discharge area and information already available.
Prepare test holes
Create representative test locations and complete the necessary preliminary checks.
Run timed observations
Record the fall in water level using the relevant test procedure.
Use the results
Apply the percolation value to the drainage-field or infiltration-system design.
The result is one part of the wider site assessment
Environment Agency guidance states that percolation testing is used to understand soil drainage characteristics and calculate drainage-field floor area. Groundwater depth and other environmental constraints also need consideration.
When testing may be useful
Projects vary, but the need usually arises when a new or replacement infiltration area is being considered.
Is a percolation test the same as a site survey?
No. It provides specific information about infiltration. A wider survey considers access, levels, the existing system, groundwater and the proposed drainage route.
Does a passing test guarantee the whole project?
No. The result informs design, but other site, environmental, regulatory and construction requirements still apply.
Can you also discuss the treatment plant or drainage field?
Yes. Testing can be coordinated with a wider conversation about the property, the proposed drainage field and a suitable sewage treatment plant.
Ask about a percolation test
Share the property location and what the test is needed for so we can discuss the appropriate next step.