Request Service Today

Why test soil before installing a septic system?

Soil testing for septic systems

Soil testing is important before a septic system is installed. It measures the water absorption rate of the soil, determines the ability of the soil to absorb wastewater and predicts the required size for the leach field.  It also analyses the subterranean conditions and the level of water table.

For example, soil with high clay content drains slowly so the wastewater will remain near the soil surface. This can lead to water logging of the area. Testing can also enable property developers to modify the design or make changes to the building structures at early stages of planning. Soil testing in the design phase saves money and time. It also prevents the septic system from breaking down due to poor soil drainage characteristics and save you time and money on expensive repairs in the future.

How are Perc Tests conducted?

  1. Dig holes (6-12 inches in diameter) in the soil 
  2. Pour water in the holes and allow the water to saturate the soil. Note the time. 
  3. Allow the water to drain away and refill the hole again with water and once the hole is empty, note down the time.
  4. Calculate the time needed to drain the hole.
  5. The percolation rate is measured in minutes/inch. 

Deep hole testing is also done to determine the drainage conditions of the soil and to determine the level of the water table. These holes are 8-10 ft deep, and the soil sample collected is inspected and tested to evaluate the subterranean conditions. 

Who can conduct the Perc Tests? 

Perc tests are mandatory and need to be submitted to the local council for approval before the septic systems are installed. Although you can do-it-yourself and dig holes in the ground, the DIY test won’t be enough to get approval from your local council. It is recommended to take professional help for perc tests and deep hole tests. Professionals can conduct the test accurately, are aware of the local rules and can suggest the appropriate wastewater treatment system for your property.

Looking for a Septic System? Let our septic system experts help you.

What kind of soils are perfect for septic systems and drain fields?

  • Sandy soils
  • Soils with low clay content
  • Loamy soils
  • Soil with gravel and clay (not too dense or too loose)

Can Perc Test fail?

A soil percolation test can fail due to reasons like:

  1. Highly permeable soil
  2. Steep slopes
  3. High water table
  4. Property located near environmentally sensitive areas - wetlands, streams, waterways or flood zones.
  5. Leach field in the path of runoff
  6. Small property lot
  7. Rocky areas 
  8. Thickly forested areas 
  9. Low-lying swampy areas 

When is a Perc Test necessary?

As the soils in each location varies, a perc test conducted by a professional is crucial. So when do you need to get a perc test done?

  • If your property doesn’t have access to the council’s sewer system and you need to install a septic system.
  • If your existing septic system is failing - poor soil drainage can lead to frequent problems.
  • You need to relocate the septic tank. 
  • New property development - house, pools, duplex, units, garage,decks etc.
  • Extensions or renovations in the property.

What to do if the Perc Test fails?

Take professional advice on the type of septic system or wastewater treatment system suitable for your property. Installing on-site wastewater management systems and placing gravel field trenches and subsurface drain pipes to transport water away from the leach field are common ways to resolve the problem.

Professional and reliable Perc Test for septic system installation 

Experienced wastewater experts can conduct perc tests and recommend solutions for wastewater treatment plants, sewage and septic systems. Schedule your professional perc test with Express Wastewater Solutions. We provide services throughout South-East Queensland. Contact us today at 1300 722 517 or complete our online booking form.

Why test soil before installing a septic system? Let our experts help you.

Not what you're looking for?

Try our search below for more information relating to septic, sewage and wastewater systems.

Search Help Section by Service

Search our information section by a specific service. Simply click the tile below.

Septic Tanks

Sewage Systems

Wastewater Treatment

Why Use Express Wastewater Solutions?


    Because we are not a manufacturer and not tied to one particular system we can always offer the best solution for your wastewater needs.


    Because we do this every day we have developed a close knit expert team for every step of the process – from plans and council paperwork to excavations, electrical and plumbing. We handle it all to make the whole process as stress free and quick as possible.


    Most people have never installed a home sewerage treatment plant and don’t know the next step, that is why we offer a free 30 minute phone consult with one of our experts to point you in the right direction.


    We handle your wastewater installation from start to finish we can deal with all the trades, council everything so you don’t have to worry about a thing.


    Have peace of mind knowing that Express are licensed, insured professionals that will do your job right the first time.


    Not sure what system is right for you, or want to know if your system is working properly? Just give one of our friendly wastewater experts a call and they will be more than happy to help.


    We will always look to repair your system rather than replace it if it does not need to be, which will generally save large amounts of money sometimes up to and over $10,000.