Below we will outline how to perform a percolation test for foul water. A percolation test requires at least two test pits. Locate the test pits where you are planning to install the soakaway system and dig to the planned depth below ground. Dig the test holes, mm square to a depth at least mm below the required invert level of the infiltration pipe. Once dug, you should fill them with water. If, after six to twelve hours, the water has not drained away, the percolation test has failed.
The answer gives the average time in seconds Vp required for the water to drop 1mm. You have to repeat this percolation test three times in each pit. How to calculate the required surface area for the soakaway system With the previous result Vp , you can now calculate how much surface area you need to house your soakaway system:.
The result A will be the area in m2 required for the soakaway system. Our installer will perform further calculations to find out the length of pipes required. How does a soakaway system work? A soakaway system or drainage field discharges the effluent from septic tanks and sewage treatment plants to ground.
It is a series of perforated pipes placed in trenches and arranged so that the effluent disperses through the ground for further treatment. This way, there is no risk of contamination. The solids from the sewage sink to the bottom of your septic tank, or packaged treatment plant, and get removed when the tanks are emptied every years. Licensed waste disposal companies do provide this maintenance service in the UK if you need it. Why is the type of soil of my property so important? A site assessment will determine whether or not a particular site can achieve this.
In all cases where an application involves a proposal to use a septic tank or other on-site treatment system, a site assessment is required.
Applicants must carry out a site assessment in advance of making a planning application. A percolation test or a perc test is a test to determine the water absorption rate of soil that is, its capacity for percolation in preparation for the building of a septic drain field leach field or infiltration basin.
The results of a percolation test are required to properly design a septic system. In its broadest terms, percolation testing is simply observing how quickly a known volume of water dissipates into the subsoil of a drilled hole of known surface area. While every jurisdiction will have its own laws regarding the exact calculations for the length of line, depth of pit, etc.
We had our percolation test done by a local tester. Sound man he was anyway. Holes were dug an tested. I believe the test took over one hour despite our assumption its a quick 5 to 10 minute percolation test! Rookies making assumptions I suppose. After an hour — we learned that we had passed! Anyway, we got the job done and it was a great feeling.
We drove away very satisfied that day. Divide this time by mm. The answer gives the average time in seconds Vp required for the water to drop 1 mm. The test should be carried out at least three times per trial hole with at least two trial holes. The average figure from the tests should be taken.
Drainage field disposal should only be used when percolation tests indicate average values of Vp of between 12 and and the preliminary site assessment report and trial hole tests have been favourable.
This minimum value ensures that untreated effluent cannot percolate too rapidly into ground water. Where Vp is outside these limits effective treatment is unlikely to take place in a drainage field. However, provided that an alternative form of secondary treatment is provided to treat the effluent from the septic tank, it may still be possible to discharge to a soakaway. Please contact Building Control if your Vp falls outside this band.
Record the results of your percolation test on the percolation test - results and drainage field calculation form and return it to us with the Environment Agency Consent to Discharge. Read about cookies we use , which are small files that go onto your computer to collect information about how you browse our website.
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