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How To Do A Soil Percolation Test

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An integral part of a septic system is the leach field. The leach field is used to collect the effluent water coming from a septic tank and disperse it into the soil throughout the field. As the effluence passes through the soil, it is naturally treated by organisms in the ground until it is no longer a biological hazard in a healthy field. However, over time the bottom of the leach field can become compacted and cause back-ups into the tank and house. You should do a percolation test to make sure the field is still draining like it should be for the soil type and conditions in the field. Here is how you can do a soil percolation test.

You Will Need:

  • Spade Shovel
  • Water
  • Timer
  • Wood Stakes

Digging Test Holes

You have to be extra careful when digging holes in an operating leach field. A leach field is basically a series of pipes that run through the field to disperse the effluence coming from the septic tank, and breaking one or more of those pipes could lead to further problems and repairs. So, you should also avoid using heavy machinery like a backhoe to dig the holes unless you know exactly where the pipes are located. Instead, use a hole digger to dig a hole 3 to 6 feet deep with a diameter of between 6 to 8 inches. You should at a minimum dig a hole in the middle of the leach field and at each corner – the holes should be uniform in diameter and depth.

The Test

Fill each hole up with water and time how long it takes the water to drain out of each hole with a timer. Place a wooden stake in the ground that you can write on by each hole. Give each hole a number and write the number on the stake – you should also mark the depth and diameter of each hole on the stake. Write the time you filled up the hole with water on each stake, too. Leave the stake in the ground by the hole. Write the end time on the stake as each hole completely drains out. Repeat this process several times for each hole to get an accurate reading of how long it is taking for the water to drain out of each hole. The holes should drain at an average of 10 minutes per inch if the leach field is draining well. If it drains too fast or too slow, you should consult with a leach field specialist like Mr Bob to talk over your options.