Septic Systems:

Inspecting Aerobic and Conventional Septic Systems: What Home Inspectors and Homeowners Need to Know

When you’re buying, selling, or maintaining a property with an on-site wastewater treatment system (OWTS), a thorough septic inspection is essential. Many Texas homes—especially in rural or semi-rural areas—use either conventional septic systems or aerobic treatment units (ATUs). These two systems function very differently, and as a home inspector (or a homeowner), understanding how they work can make the difference between a smooth sale and an expensive surprise.

This article covers:

• The difference between conventional and aerobic systems

• How each system works

• What inspectors look for

• Failure signs

• Maintenance expectations

• How to properly document findings for clients

The goal is to provide clear, useful, SEO-friendly information without fluff.

1. Understanding the Two System Types

Conventional (Anaerobic) Septic Systems

A conventional septic system uses a buried tank and a drain field (also called a leach field) where wastewater separates into solids and liquids. The solids settle in the tank, and the effluent flows into the soil, where natural bacteria break it down.

Pros:

• Simpler design

• Lower upfront cost

• Fewer mechanical components

• Cons:

• Requires a large drain-field area

• Dependent on proper soil conditions

• More prone to overload if not pumped regularly

Aerobic Treatment Units (ATUs / Aerobic Septic Systems)

Aerobic systems use oxygen and mechanical aeration to break down wastewater more efficiently. These systems often include multiple chambers, an aerator, and a pump tank. Effluent quality is significantly higher than in a conventional system.

Pros:

• Better effluent quality

• More flexible site placement

• Smaller footprint

  Cons

• Requires electricity

• More mechanical parts to fail

• Higher maintenance costs

Why the difference matters

Inspection requirements vary significantly:

• Aerobic systems include electrical and mechanical components that must be checked.

• Conventional systems rely more on tank condition, sludge/scum levels, and drain-field performance.

2. Pre-Inspection Preparation

Before stepping foot on the property, preparation ensures a more accurate inspection.

Review property information

• Ask for septic permits, installation records, or maintenance logs.

• Look for system type, age, size, pump-out history, and last service date.

• If no records are available, note that in your report—it matters for valuation and risk.

Gather necessary tools

Flashlight, probe rod, gloves, wastewater-safe PPE, camera, basic sludge sampler, and your standard septic inspection checklist.

Initial on-site observations

• Confirm tank location(s), risers, lids, control panels (for aerobic), and drain-field boundaries.

• Observe site conditions: puddling, lush green patches, depressions, odors, or any evidence of surfacing effluent.

3. Inspection Checklist for Conventional Septic Systems

Step 1: Plumbing Fixture Evaluation

Inside the home, check for:

• Slow drains

• Gurgling sounds

• Sewage odors

• Backups under load

A brief flow test can help identify whether the system is handling normal wastewater volume.

Step 2: Inspecting the Septic Tank

• Open risers/lids safely. Never place your head or body directly over the opening.

• Inspect for cracks, infiltration, rusted lids, unsafe covers, or missing bolts.

• Look at the scum and sludge layers (if possible). Excessive buildup suggests overdue pumping.

• Confirm inlet and outlet baffles are intact. Broken baffles allow solids to enter the drain field.

• Check the liquid level—too high may indicate a clog or drain-field issue; too low may indicate a leak.

Step 3: Inspect the Drain Field

Walk the entire dispersal area:

• Look for standing water or soggy soil

• Observe for unusually green or thriving grass

• Feel for spongy ground underfoot

• Note any visible settling or depressions

• Ensure no driveways, structures, or heavy landscaping were built over the field

Step 4: Report Deficiencies

Sample report wording:

“Elevated liquid levels were observed in the septic tank, which may indicate restricted flow or drain-field saturation. Recommend further evaluation by a licensed septic service provider.”

4. Inspection Checklist for Aerobic Treatment Units (ATUs)

Aerobic systems require all the checks of conventional systems plus mechanical and electrical testing.

Step 1: Inspect Control Panel

• Ensure power is on

• Test alarms (audible and visual)

• Look for corrosion, water intrusion, or loose wiring

• Check timer settings if the system uses timed dosing

Step 2: Aeration System

• Verify the aerator is running

• Listen for proper pump tone (not straining)

• Check for visible bubbling in the aeration chamber

• Look for signs of odor—strong odor may indicate aeration failure

Step 3: Pump Tank & Dispersal System

Depending on system type, this may include spray heads or subsurface drip lines. Inspect for:

• Functioning pump

• Float switch operation

• Proper spray patterns

• No ponding around spray heads

• Secure and upright spray risers

• No surfacing effluent over drip lines

Step 4: Disinfection

Many aerobic systems use chlorine tablets or UV disinfection. Check that:

• Chlorine tablets are present and correctly placed

• Chlorine tablet type is appropriate (non-pool tablets)

• UV units (if present) have no visible damage

Step 5: Report Deficiencies

Example wording:

“Minimal aeration was observed in the aerobic treatment chamber and a strong sewage odor was present. This suggests aerator malfunction. Recommend evaluation and servicing by a licensed aerobic system technician.”

5. Common Failure Signs Both Systems Can Show

Whether conventional or aerobic, some symptoms indicate trouble:

For Conventional Systems

• Lush grass over the drain field

• Backups inside the home

• Slow drains

• Standing water over the drain field

• Sewage odors near tank or field

• Tank overfilled or underfilled

• Settling or depressions in drain-field area

For Aerobic Systems

• Aerator not running

• Alarm light/siren activated

• Odors from tank or spray area

• No chlorine tablets

• Ponding around spray heads

• Drip field surfacing water

• Short cycling of pump

6. Maintenance & Lifespan Considerations

Conventional Systems

• Pump every 3–5 years (more with high occupancy)

• Protect drain field from vehicles and structures

• Avoid flushing grease, wipes, chemicals, or excessive water

• Repair dripping faucets or running toilets—these overload the system

Aerobic Systems

• Usually requires professional service 2–4 times per year

• Keep chlorine tablets stocked

• Ensure constant electrical power

• Check alarms monthly

• Spray nozzles should be kept clear and upright

• Expect periodic replacement of mechanical parts like pumps and blowers

7. Communicating Findings to Your Client

Clear communication builds trust and helps clients make informed decisions.

Tips for effective reporting:

• Break the report into sections: tank, aeration/pumps, dispersal field, alarms, maintenance needs

• Use simple, direct language

• Include photos of every component

• State clearly whether a system is functioning, marginal, or not performing

• Identify any immediate health/safety concerns

• Recommend appropriate specialists

• If records were missing, document that

Sample clarity-focused statement:

“The aerobic system’s alarm panel was inoperative at the time of inspection. This prevents the system from alerting the occupants to a malfunction. Recommend repair by a qualified aerobic system technician.”

8. Why Septic Inspections Matter

For buyers, sellers, and homeowners, septic inspections:

• Prevent costly repair surprises

• Help negotiations when buying a home

• Protect groundwater and the environment

• Ensure the system is properly sized for the home’s use

• Increase confidence in the property’s overall condition

• Protect health by preventing sewage exposure

9. Quick Summary Checklist

Conventional System

• Check sludge/scum levels

• Verify baffles

• Inspect tank structure

• Evaluate drain-field performance

• Confirm liquid level

• Recommend pumping if needed

Aerobic System

• Check aerator function

• Inspect control panel and alarms

• Evaluate pump tank and spray/drip dispersal

• Ensure proper disinfection

• Document any odors or ponding

10. Final Thoughts

Whether it’s a simple conventional system or a more complex aerobic unit, septic inspections require attention to detail, understanding of wastewater behavior, and the ability to communicate findings clearly. A well-conducted inspection protects the homeowner, the buyer, and the property itself.