How To Carry Out A Percolation Test

1.35 Fill the 300mm square section of the hole to a depth of at least 300mm with water and

allow it to seep away overnight.

1.36 Next day, refill the test section with water to a depth of at least 300mm and observe the

time, in seconds, for the water to seep away from 75% full to 25% full level (i.e. a depth of 150mm).

Divide this time by 150. The answer gives the average time in seconds (Vp) required for the

water to drop 1mm.

1.37 The test should be carried out at least three times with at least two trial holes. The

average figure from the tests should be taken. The test should not be carried out during abnormal weather conditions such as heavy  rain, severe frost or drought.

1.38 Drainage field disposal should only be used when percolation tests indicate average

values of Vp of between 12 and 100 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 groundwater. 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 tanks, it may still be possible to discharge the

treated effluent to a soakaway.

1.35 Fill the 300mm square section of the hole to a depth of at least 300mm with water and

allow it to seep away overnight.

1.36 Next day, refill the test section with water to a depth of at least 300mm and observe the

time, in seconds, for the water to seep away from 75% full to 25% full level (i.e. a depth of 150mm).

Divide this time by 150. The answer gives the average time in seconds (Vp) required for the

water to drop 1mm.

1.37 The test should be carried out at least three times with at least two trial holes. The

average figure from the tests should be taken. The test should not be carried out during

abnormal weather conditions such as heavy rain, severe frost or drought.

1.38 Drainage field disposal should only be used when percolation tests indicate average

values of Vp of between 12 and 100 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 groundwater. 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 tanks, it may still be possible to discharge the

treated effluent to a soakaway.

For more free information please visit https://www.septictank.co.uk