Percolation Test: What is it? 

What Is Percolation Test?

A percolation test is a process for evaluating water drainage in various soils. It is useful for a variety of purposes; for example, if you are thinking about a new septic tank installation, naturally, a leach field should also be constructed. For this, you need to know the soil’s permeability. Other beneficial reasons for a percolation test can be planning a building design, or if you are interested in agriculture, you can assess whether your land is suitable for agriculture. If the waste and pollutant cannot be filtered out properly by the soil, you will end up with collected sewer water, unfortunately, and this will quickly turn into a foul-smelling health issue that needs very expensive repairs.
A percolation test also ensures that the drainage field will allow discharge to soak into the soil without making any pools at the ground and filters the waste at a rate that fully removes contaminants.

How Is It Done?

• Step 1: First, you need to dig out the percolation hole. The hole should be 300mm x 300mm broad and 300mm lower than the anticipated invert level of the septic tank output pipe.
• Step 2: After clearing away any loose debris inside the hole, fill the hole with water up to 300 mm deep and let it get absorbed overnight.
• Step 3: The next day, redo the whole test again with water to a depth of at least 300 mm. Then, observe how rapidly the water seeps away. When the water level decreases to about 225 mm, begin timing in seconds to see how long it takes for the water level to reach 75 mm. This shows how long it took the water level to decrease by 150 mm. Divide this amount by 150 to get the average time it takes for the water level to drop 1 mm—this is known as the Vp number. We recommend repeating the test at least three times to ensure accurate results.

Interpreting Results

A VP number between 15 and 100 is essential to allow wastewater to penetrate the soil. Any other numbers can indicate something is wrong with the soil’s permeability. In this case, we advise you to talk to professionals of a septic company like Septic Blue. You can ask any questions you might have regarding septic systems if you want them installed or may need septic tank pumping if the tank hasn’t been maintained for a while now.