Percolation Tests in Horsham: A Step-by-Step Guide
If you are planning a new septic tank drainage field, a sewage treatment plant or a soakaway in Horsham, you will almost certainly need a percolation test. It tells you how quickly water drains into your ground.
Why the test is needed
Building Regulations Approved Document H requires proof that the ground can absorb treated effluent or surface water. Building Control and planning officers will usually ask to see the results before work is signed off.
How the test is carried out
The method follows the British Standard approach. In outline:
- Test holes are dug where the drainage field or soakaway will go
- The holes are pre-soaked so the soil is properly wet
- Water is added and the time it takes to drop is recorded
- The test is repeated and an average percolation value is calculated
What Horsham ground conditions mean
Much of the Horsham district sits on Weald Clay, which drains slowly. A poor result does not mean you cannot build. It may mean a larger drainage field, a raised mound system or a treatment plant discharging to a watercourse instead.
We supply a clear written report you can pass straight to your architect or Building Control.
Frequently asked questions
How long does a percolation test take?
Usually one to two days on site, depending on how quickly the ground drains.
Can a test fail?
A test does not pass or fail as such. It gives a value that decides which drainage design is suitable.