What Is A Septic Inspection: What It Includes?

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Hubert Miles

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According to InterNACHI, it is recommended a septic tank be inspected once a year. The average household needs to have a septic tank pumped every three to five years. It’s best to have a thorough septic inspection performed when the tank is being pumped because all sides and the tank’s floor are visible.

So, what is a septic inspection, and what does it include?

A septic inspection is a full review of the septic tank to check the water level. The inspector will remove the septic tank cover and observe the flow of wastewater through the septic system by running water from the house to the septic tank and the leach lines. Leach lines are a system of perforated pipes that disperse the effluent from the septic tank into the ground. In some cases, a septic system may need to be pumped to perform the inspection.

Below is an in-depth look at what to expect when you have a septic inspection scheduled.

Inspection Of The Drain Pipes

This part of the inspection focuses on checking the drain pipes to see if they are in good condition without any leaks.

The pipes you can expect in a septic tank are typically made from PVC plastic. That means they can easily crack and begin to leak if something heavy or hard is forced onto them where they run in the yard.

Septic inspectors can tell if there are cracks in the pipes by inspecting the ground around the piping. The ground where the pipes underneath have cracked will be saturated with wastewater.

During the inspection, the inspector will also check to see the water flow from the house into the tank and whether there is an overflow when more water is introduced into the tank.

If the team comes across such a saturation of wastewater, they will dig down until they reach the leaky pipe to see the extent of the damage.

Once this is done, the team will fix the problem.

septic tank

Review The Effectiveness Of The Septic Tank

The septic tank can become inefficient over time because it is backed up. In addition, sludge in the tank builds up due to solid waste that won’t decompose even with aerobic bacteria. The buildup is normal and to be expected with any septic tank.

Sludge lines up the floor of the septic tank in layers. With time and without proper pumping and inspection, the sludge will continue increasing until it eventually overflows.

The inspector will check whether the tank is performing efficiently for the volume of waste running through it. If it is not, they will advise on the correct size or using solutions like

  • Using a different microbe blend or bio-activator
  • Installing and maintaining an aeration system with diffused air in the tank
  • Breaking up compacted sludge
  • Increasing the amount of your current microbe blend

Measurement Of Septic Tank Sludge

measuring solid waste buildup 2d

The inspector will measure the sludge depth in your septic tank.

Typically, a septic tank should be pumped when the scum and sludge layer displace 30% of the tank’s overall volume.

The team will use a sludge judge for the measurement. A sludge judge is a hollow, long plastic tube with a valve at the bottom for measuring the sludge/scum layer.

Scum develops when grease or oil enters the tank.

To measure the scum, they will stick the sludge judge into the tank until it breaks past the scum layer. Then, when they pull out the tube, the level of the scum layer is visible on the tube.

For sludge measurement, the team pushes the tube until it reaches the bottom of the tank. As the tube is removed, the measuring valve at the bottom captures the liquid versus solid profile of the tank. That is how the inspector can tell the amount of sludge in the tank.

The inspector can also calculate for you how much sludge you should expect over two years. 

They do this using the following metrics:

  1. Sludge layer thickness
  2. Scum layer thickness
  3. The capacity of the septic tank
  4. The amount of solid waste in the wastewater
  5. The amount of wastewater
  6. The septic tank retention time

This information helps the inspector tell when you need to schedule the tank’s next pumping and cleaning session.

  1. Checking The Leach Field

During the installation of your septic tank, a leach field is created. The leach field is the soft absorption field with unsaturated soil.

A shallow excavation is made and laid with gravel. Then, perforated pipes, known as leach pipes, are laid in the area before they are covered back with the soil.

The perforated pipes leak the effluent (liquid from the septic tank) slowly into the soil. The effluent trickles through the gravel draining into the earth below. Of course, the wastewater is treated with microbes and bacteria before it reaches the water table.

The inspector will walk over the leach field, looking for any squishy ground or odors that indicate a leak in the leach lines.

Suppose the wastewater is rising to the top of the soil. In that case, it may be because of a layer of biomaterial sludge known as biomat, a gelatinous, water-tight, black layer that covers the leach lines.

It blocks the leach pipes from percolating the effluent into the soil.

Typically, biomat is not a bad thing because it stems from the flow of water by allowing only a small portion out of the pipes at a time. But it becomes a problem when there is overgrowth. Too much of it, and you have a backed-up system.

The inspection team will also check the field’s risers for any leaks. Risers are the pipes sticking out of the ground in the leach field that allow you to check the drain’s system.

They will remove the caps off the risers and check inside the pipe with a flashlight. If there is water in the pipe, the system is not draining correctly and needs repair.

Watch a professional septic inspection for a real estate transaction.

It Is Possible To Fail A Septic Inspection

It is crucial to pass a septic inspection because this is a critical expectation when refinancing, buying, or selling a home with a septic tank.

Passing a septic inspection is dependent on the following

  • No sign of scum, trash, or other foreign debris inside the tank
  • A natural flow of wastewater through the tank
  • No evidence of sludge in the tank

During the inspection, these are the three main areas the inspector will focus on. A healthy septic tank is like a well-oiled machine so that the inspector will focus on the tank components.

The inspector will be focused on the following sequence to determine the health of the tank:

  1. All water coming out of your house enters the tank via one main drainage pipe.
  2. It enters the septic tank, which effectively holds the wastewater until the solids (sludge) settle to the bottom, and the grease (scum) floats. The wastewater is treated in the tank.
  3. The wastewater leaves the tank into the leach field, while the T-shaped outlet doesn’t allow the scum and sludge to leave the tank into the field.
  4. The wastewater enters the soil through perforated pipes, where it is treated again as it filters through the soil.

If any of the above steps doesn’t flow naturally, you will fail the inspection.

The good news is that if you fail an inspection, the inspector will recommend what should be done. Then, after you finish with the repairs, you can schedule another inspection.

Preparing For A Septic Inspection

Before a septic inspection, it is best to call in a professional to check out your tank and repair wanting areas.

Shop around for a licensed septic inspector to come and identify areas that require work. Home inspection companies have licensed inspectors on staff to offer these services.

Retrieve past installation and maintenance records to help the inspector understand the health of your tank. These documents also provide a history of the tank and any previous problem areas.

Create a budget for any of the potential items that you may need to replace. That includes water pipes, leach pipes, and the septic tank itself. You may need to budget for a complete overhaul of the leach field depending on the extent of biomat in the area.

If your leach field is leaking, begin reducing the water use by 30% to allow the field to drain and begin to recover. Check out this video to see how to address an entire leach field.

Inspecting The Four Common Septic Tanks

There are four common materials used worldwide in making septic tanks. These are

  • Concrete
  • Plastic
  • Steel
  • Fiberglass

Concrete Septic Tanks

concrete septic tank will remain in good shape with regular pumping and maintenance for 40 years. That means that it will probably need about 13 inspections during that period.

What to expect

The cover of a concrete septic tank is typically rated thick enough to have a car driven over it. So on that front, it means that it is hard for the cover to break.

However, an inspection of the concrete septic tanks focuses more on the tank’s body and seepage into the soil and water table.

Cracks in the body of the tank can occur if it was built using poorly mixed concrete. The sub-standard mix will erode quickly and badly, leaving the tank vulnerable to cracks.

The inspector will check for any cracks along the body of the tanks.

If the cover is not secure, surface runoff can cause the tank to flood and overflow during the rainy season. Groundwater can also seep into the tank, increasing the volume and causing an overflow. Flooding on the ground will tip the inspector to a leaning problem.

Baffles (the drains that prevent solids from flowing out of the tank) are also likely to get damaged, allowing soil into the leach field.

Lastly, the inspector will check if the concrete tank is well settled in the soil. That is because the concrete can settle poorly, causing the tank to tip, which results in leaks and poor operation.

Steel Septic Tanks

steel septic tank has a lifespan of 20 to 25 years. After that, it will succumb to rust which causes it to collapse and spill the contents.

What To Expect

Unfortunately, even before the tank itself deteriorates, its baffles will be long gone. So a septic tank inspector will be checking the baffles and overall integrity of the steel.

Once the baffles rust, they will release sludge and scum into the leach field. So, the inspection team will be looking for any signs of rust and deterioration on the cover. That is because rusted covers can collapse when one is standing on top of them, resulting in death.

Children are especially vulnerable to this hazard as they play in the yard.

Also, the team will look at the leach field for any signs that solids have seeped into it. They will also check the soundness of the bottom of the septic tank.

Plastic And Fiberglass Septic Tanks

Plastic and fiberglass septic tanks are inspected similarly because their materials are also similar in composition.

They are both very resistant to corrosion and cracks, unlike steel and concrete. You can expect to use a fiberglass septic tank for 30 to 40 years, while a plastic tank can go for at least 30 years.

What To Expect

The inspector will check whether the plastic/fiberglass plug at the bottom of the tank has been lost. If it is dislodged, it could mean there has been seepage into the surrounding soil.

The team will also check for any damage during installation that may cause breakage on the tank. Unfortunately, such a crack may not be evident at first until the tank is pumped. But the leak in surrounding areas will give the inspector an idea of what is going on.

Also, shallow levels of effluent can signify a crack or leak.

Finally, they will check for any underground water forcing the tank upward. Fiberglass and plastic are particularly buoyant, especially when empty, like at the initial installation.

If installed too close to the water table, the water pushes the tank upwards, cracking connections like baffles and pipes. The inspector will look out for any loose connections and inquire about the last records of pumping the tank.

Are you looking for instructions for a DIY septic inspection?


A septic inspection is essential for the overall health of your family, pets, and the environment.

Since the septic tank is buried in the ground, a leaky tank introduces harmful bacteria into the soil. These bacteria find their way into the water table, contaminating the water and making it unsafe to drink.

Regular inspection of the septic tank prevents that from happening.

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Hubert Miles

I've been conducting professional home inspections since 2002. I'm a licensed Home Inspector, Certified Professional Inspector (CPI), Certified Master Inspector (CMI), and FHA 203k Consultant. I started to help people better understand the home inspection process and answer questions about homeownership and home maintenance.
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