Septic Tank Soakaway

8 Jan, 2014

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Is your soak away failing on your septic tank?  If so here is some information you will find useful

First of all what are the symptoms of a failing septic tank soak away?

  1.  Septic tank backing up and over flowing, if your soak away has failed your septic tank will fill up very quickly, it could be also that you have a high water table where you live and the soak away even though constructed adequately will not work due to poor ground conditions.
  2. Soggy polluted ground and bad smells, another symptom is visible pollution on the ground surrounding the soak away this tends to be caused by either the whole of the soak away area becoming polluted and not having any percolation or because part of the soak away has been damaged or collapsed and all the effluent is discharging to a small area of the ground stoping the ground from being able to cope with the discharge from the septic tank.

If you are experiencing either one of these symptoms what should you do?

First of all you need to find out what your ground conditions are like, it maybe the case that the ground conditions have changed since your soak away was constructed so you need to do some tests, here are the steps you will need to take to carry out a proper percolation test for a septic tank soakaway

  1. Excavate a hole 300mm square to a depth 300mm below the proposed invert level of the soakaway pipes.
  2. Fill the 300mm square hole to at least the 300mm mark and allow to soakaway over night.
  3. On the next day, fill to the 300mm mark again and observe the time it takes to soakaway in seconds, from 70% full to 25% full.
  4. Carry out this test at least 3 times in at least 2 different places.

Once you have carried out the percolation test you can workout how big your soak away needs to be and weather it is viable for you to install a soak away in the area you have, this is what you do next.

Divide the time taken by 150.  The answer gives you the average time in seconds (V).

Drain fields or soakaways should only be installed when the results are between 12 -100.  If the value is outside these parameters you might need to install a sewage treatment plant.

Now that you have done the percolation test you can start to plant your new septic tank soak away or drainage field, here is how you can calculate the size of area to cover using the information from the percolation test

To calculate the size of the soakaway, use this formula:

Area = P x V x 0.25

Where:

P= the number of persons served

V= percolation test value

 

 

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