Before a septic system can be properly designed and installed, a percolation test, also called as a perc test, proves to be one of the most important aspects in such a process. Which of septic systems will be appropriate for the given conditions will entail knowing more about the ground characteristics, for instance the suitable soil texture as well as absorptivity and filtration of wastewater.

Describes a Percolation Test.

A percolation test determines the rate at which water drains away from the soil and how many hours or days it would take this water to completely leave the soil. This lets one know if the depleted effluent from the septic tank can be adequately absorbed by the soils in the drain field. The waste water can be reinfiltrated into the ground since the soils retain and break down the pathogens and many chemicals that may come along hence adequate percolation is very important.

When is a Percolation Test called for?

Typically, one needs a percolation test in the following situations:

Prior to installing a new septic tank to make sure that the center will be able to accommodate it,

Changing a septic system either replacement or upgrade: In a process of replacing or upgrade such existing system particularly where residential units are being expanded, with installation of such pumps.

Building on virgin land: If you are putting up a house on a new piece of land, the local welfarists may require you to undergo a perc test before they issue you with a building permit.

What are the procedures involved in conducting a percolation test?

This often involves taking a series of test pits in a proposed drainfield area and measuring time taken for water to evaporate. The typical steps are outlined below:

This is done away from wells, streams and buildings usually on a flat piece of land known as the drain field site; in which the effluent from the septic tank will be discharged.

This is often determined by local laws where distances known as setback distances require that the drain field maintains a given distance away from any water sources, site boundaries and buildings.

In accordance with the health department’s regulations very many holes may be dug on the particular spot with the aim on creating a septic drain field often size 6 to 12 inches wide and 12 to 36 inches deep at times.

Some areas actually specify that the best method of boring the holes is that there should be a variation in the depth to simulate the entire drain field area.

Normally done in a number of places within the field, test holes guarantee a degree of reliability in the findings from the field.

Soaked holes are soaked with enough water before the experiments and therefore allow clay saturation to take place, thereby imitating situations that the drain field is likely to experience when the system is operational.

This step of pre-soaking of soil is usually performed 12 to 24 hours prior to the actual percolation test and it is done in order to evaluate the natural absorption rate of the soil.

Each of the holes is filled with water and the time taken to percolate through the test hole with a given volume of water is measured.

Normally, the tests are carried out in stepwise manner that is, every 30 minute or 1 hour duration or other intervals until a constant decline of the water is observed.

In the case of water test families – the percolation rate is measured by the speed at which water drops one inch and its recording interval is minutes per inch MPI.

Outcomes in Percolation Rate:

Coarse sand or gravel which can be noted to be very well drained soil presents little time for the effluent to be adequately treated thus enhancing the risk of water contamination.

Perc rate: This could be fit with a traditional system and may require additional treatment.

Moderately permeable soils are ideal for means with a steady water drainage rate as septic systems help in treating the effluent by allowing the soil sufficient time to work on it.

This percolation rate, generally suitable for standard septic systems, is suitable for 1 to 30 MPI rates.

Conversely, if the soil is too permeable, that is has too little clay such that flood water drains too fast, it may distribute wastewater incorrectly leading to system unresponsiveness and failures.

Perc rate > 60 MPI: This might be too a standard systems and management practices, such as aerobic treatment systems or mound systems may need to be employed.

Factors Influencing Results of the Percolation Test:

Nature of The Soil:

Sandy soil: possibly, many do not drain hinder enough to soil.

Loam soil is best for septic systems and this only allows limited drainage.

Clay soil: Very poorly draining soil and will often need alternative systems.

Ground Water Fluctuations:

High water tables may hinder the drain field’s ability to spread the effluent over a large area. Wetland areas may call for certain options such as mound systems.

Time of The Year:

The time of the year, the perc test is done may affect the test results. A wetter season may cause the soil to have a longer off-season, as opposed to dry seasons.

Land and Gradient:

Drain fields are best located in flat areas, but problem might arise with steep slopes.

What Happens When Percolation Test Fails?

A percolation test fails; this means that a standard septic system cannot be adequately installed in the ground you have. You may immediately investigate other options in this situation:

These include Mound wastewater treatment systems systems, aerobic treatment units or ATUs and irrigation systems.

Site grading adjustments or importing soil amendments like gravel may also be useful sometimes in improving drainage.

Shift the Drain Field: If any portion of the lot fails the perc test, other portions of the lot may be investigated for better results.

State and Local Laws:

Many governments such as states, counties, or municipalities have established broad differences in the criteria for percolation testing. While local health departments typically set the criteria for passing perc tests according to Ebersole et al (2010), other areas could have their own rules on the frequency, depth, and methods of the tests Donegan et al (2012). To find the rules in your area, make sure you seek consultation from a septic system contractor or any other local health department.

Essentially, a percolation test helps to determine if a septic tank system can be accommodated within the basin. Knowledge of the rate at which perc estimates a high hydrodynamic loading system does not help in avoidance of treatment disposal and treatment without pollution or back-ups. If there are indications that the soil is not conducive for putting up a conventional septic tank then other alternatives exist to rectify the situation.