Percolation Test: Failure or Victory?!

CM Environmental undertake percolation tests for our customers, in order to size a suitable soakaway or drainage field for the site. We also offer instructions if this is something the customer is capable of doing themselves, if this is the preferred option.

A percolation test normally involves digging 2 or 3 holes, at the depth of the prospective outlet of any tank, in order to flood it with water, then timing how long it takes to drain away, to determine the permeability of the ground. This indicates what size drainage field (also known as a soakaway) is required for a septic tank (also known as a cesspit in years gone by.)

One of our engineers recently showed real CM determination to get the best result for our customer, digging more than 5 holes to try to find a place to locate a suitable soakaway. He dug these at varying depths and locations and stayed on site all day to get this done (we didn't charge any more for this service- it was what the customer required.) Unfortunately, he repeatedly digging into the existing failing soakaway, meaning the ground was not safe to install a new soakaway in that location. In the spot he did eventually find, the percolation failed to get a suitable reading, meaning the ground was not suitable to drain away efficiently. On this occasion the ground he excavated was solid clay so it meant no water drained away. Ground can also "fail to get a reading" by actually being too permeable for a soakaway; it can flow away too quickly (meaning it has not achieved a safe level of cleanliness to discharge to ground.)

It isn't a problem though - as with all of our customers, CM Environmental have striven to find the best solution to this problem. We are planning to install a secondary foul water treatment tank on the existing septic tank, effectively turning an old septic into a brand new treatment plant. The customer is happy to guarantee the structure of the existing septic tank (after seeking advice from a structural engineer we recommended) so we can fix the soakaway problem by eliminating it. Once we install the secondary treatment tank, the customer will be able to discharge clean water into a nearby running ditch or watercourse. CM are even helping with the Environment Agency Binding Rule adherence by providing a "first year free of charge" ongoing service contract to the unit following install.