Using a metal detector for septic tank location can save you time, effort, and a whole lot of unnecessary digging. Whether you’re a homeowner trying to pinpoint a long-forgotten septic system or a contractor working a residential or commercial site, choosing the right detector and using the correct technique can dramatically improve accuracy and reduce guesswork.
While metal detectors can easily locate septic tanks with metal components, like steel lids, rebar-reinforced concrete, or metal access risers, they may not detect tanks made entirely of plastic or fiberglass. Our team at Garrett will walk you through the entire process, from selecting the ideal metal detector to understanding how different tank materials affect detection.
Key Takeaways
- Metal detectors can effectively locate septic tanks that contain steel, rebar, or metal lids.
- Start your search by tracing the main sewer line from the house to the likely tank area.
- Most septic tanks are buried 10–25 feet from the home and 2–4 feet underground.
- Use a grid search technique to scan and confirm signals from buried metal objects.
- For plastic or fiberglass tanks, use alternative methods like soil probes, public records, or visual clues.
- Garrett’s AT Max metal detector offers deep detection, wireless audio, and advanced features ideal for septic tank locating.
Understanding When a Metal Detector Will Work
Not all underground tanks can be found with a metal detector. Detectors work by sensing metal objects beneath the ground, so the tank’s material determines whether detection is possible.
A metal detector for septic tank searches works best on tanks that contain steel, iron, rebar, or metal lids. Compared to ground penetrating radar, metal detection is often cheaper, more inexpensive, and easier for homeowners and small businesses to use.
Plastic and fiberglass tanks require other methods such as a metal soil probe, plumbing records, or radar-based tools.
What Types of Septic Tanks Can Be Detected?
Concrete Tanks
Concrete tanks are common on older properties and often include rebar or metal lids. While concrete itself is not metal, the internal reinforcement and septic lid usually produce a detectable signal, even when covered by dirt or grass.
Steel Tanks
Steel septic tanks are fully metal and highly detectable. These tanks are often buried only a few feet below the surface, making them easy targets for most detectors, even entry-level models.
Fiberglass and Plastic Tanks
These lightweight tanks are durable but contain no metal. A metal detector cannot detect them. Locating these tanks requires ground penetrating radar, probing, or following plumbing lines from the house.
Step 1: Start at the Sewer Cleanout
Before using your metal detector, identify the direction of the septic system.
Locate the Cleanout Access Point
The sewer cleanout is usually a capped vertical pipe found in a basement, crawl space, or garage. This pipe connects your home’s plumbing to the septic tank and provides a reliable starting point.
Trace the Pipe’s Path Outdoors
Mark where the pipe exits the house foundation. This point determines the direction of the drain line and helps you locate the tank area without guessing.
Step 2: Understand Septic Tank Placement Guidelines
Knowing standard placement rules reduces the amount of land you need to search and improves detection precision.
How Far Are Septic Tanks from the Home?
Most tanks are located 10 to 25 feet from the house and buried 2 to 4 feet deep. Tanks are usually placed in open yard areas for easier maintenance and pumping access. Gravity-fed systems often place the tank slightly downhill to help waste flush properly through the drain line.
Step 3: Use a Metal Detector to Begin Your Search
Once you know the sewer line direction, begin scanning for metal objects associated with the tank.
How to Sweep for a Septic Tank
Start at the pipe exit and sweep the ground in slow, straight passes. Focus on areas 10 to 25 feet from the house. Consumer-grade metal detectors are capable of detecting steel tanks, metal lids, and rebar within typical burial depth.
Grid Search Method
Sweep the area in parallel rows, marking strong signals. Then sweep the same area in the opposite direction to confirm consistency. This helps rule out interference from other metal objects like buried debris, old oil tanks, or unrelated underground structures.
Step 4: Cross-Check with Public Records
Use County or Municipal Resources
If your septic tank searches haven’t given a clear hit, it’s smart to double-check with public resources. Local agencies often store important records related to your septic tank, especially if your house was built in the last few decades.
Visit Your Local Health Department
Start with your local environmental or health department. They may have permits or inspection records tied to your property’s septic system or underground tank. These records often include basic drawings showing pipe lines, tank placement, and drain field locations.
Look for Septic System Permits or Plot Maps
Older permits might be hand-drawn, but they can still help locate the general direction and foot distance of your tank from the home. Some counties post these records online, making it easier for homeowners and small businesses to plan their search in detail.
Some Records Show Tank and Drain Field Locations
These plot maps may highlight where concrete, metal lids, or plumbing lines were originally installed. If your metal detector has picked up metal objects like rebar, steel, or iron, you can cross-reference that data with the official documents for improved accuracy.
Step 5: Dealing with Fiberglass or Plastic Tanks
Alternative Detection Methods
Some septic tanks are made from fiberglass or plastic. In these cases, a metal detector for septic tank use may not detect anything, since there are no metal objects present. Instead, try using a metal soil probe or steel probe rod to check suspected locations.
Use a Soil Probe to Gently Poke Suspected Areas 1–2 Feet Deep
A metal soil probe is a simple tool that helps you feel for resistance under the dirt. Poke about 1 to 2 feet deep, moving in a straight line across your yard. Be careful not to hurt yourself or damage the tank.
Look for Riser Lids or Inspection Covers Flush with the Soil
Fiberglass or plastic septic tanks often have septic lids or risers made from lightweight metal, plastic, or concrete. These may be flush with the surface or slightly covered by grass, mulch, or dirt. Use your metal detector to scan near these areas, some have metal handles or rebar supports.
Consider Visual Cues Like Depressions or Slightly Mounded Areas
Scan the terrain for dips or humps. These changes in elevation can signal where an underground structure like a septic tank, oil tank, or drain field might be. Natural settling over time causes uneven ground, especially near pipes or tank lids.
Step 6: Confirm and Mark the Location
Why Marking the Tank Matters
Once you’ve found your tank, marking it saves time, money, and maintenance issues down the road. It helps septic crews locate and access the septic lid for cleaning and inspections and avoids accidental digging over buried metal, concrete, or plastic components.
Use Stakes or Shallow Digging to Expose the Lid Perimeter
Use stakes or small flags to mark the outer edges. You can also dig carefully to confirm the location of the lid. If the tank is deep, you may need to dig further or use a longer probe. Keep in mind, this step improves precision for future access or landscaping plans.
Locate Septic Tanks with Confidence Using the Garrett AT Max
Our AT Max metal detector isn’t just for treasure hunters, it’s an excellent tool for practical jobs like locating buried septic tanks. With its enhanced depth capabilities, this waterproof, all-terrain VLF metal detector delivers serious performance.
Its 13.6 kHz frequency offers improved sensitivity to large, deep targets, while Z-Lynk wireless audio ensures real-time feedback with zero lag. Whether you’re scanning mineralized soil or working near saltwater, the AT Max’s True All Metal Mode, Iron Audio, and advanced ground balance make it easy to differentiate between metal debris and larger buried structures, like septic tanks, without missing a beat.
Recap: How To Find A Septic Tank With a Metal Detector
Locating a septic tank can be tricky, but with the right tools and a smart approach, the process becomes much more manageable. A metal detector is often your best starting point, especially if your tank includes metal components like lids, rebar, or steel reinforcements. At Garrett, we understand how critical accuracy is when it comes to septic system detection. Whether you’re a homeowner or small business looking to avoid unnecessary digging, we can help you choose the right metal detector, just reach out.
