How to Find Septic Tank with Metal Detector

by Michael Bernzweig

Sewage and other wastewater from your home are stored in septic tanks. If you're looking to buy a house with a septic tank, finding them can be difficult if they're hidden under grassy areas or in wooded lots. And while inspecting for them in advance isn't practical, knowing where to find them when needed can come in handy. Daily, we get the question, can you tell me "how to find a septic tank with a metal detector?" This article answers that common question and should prove helpful.

Metal detectors are useful for finding septic tanks: 

  1. Find Your Main Sewer Line
  2. Determine Septic Tank Material
  3. Using a metal detector, Mark the areas of the highest signal strength
  4. Search Perpendicularly, Using the Same Method
  5.  Mark The Location For Future Maintenance

In this article, we'll show you how to find a septic tank with a metal detector. Additionally, we'll touch on determining the tank material and what to do with all that information.

Infographic: Steps to Find a Septic Tank with a Metal Detector

As we can see from the infographic above, locating a septic tank with a metal detector is fairly straightforward. Septic tanks are generally installed around 10 to 25 feet away from the building they are attached to. Finding where your septic tank is located can be done with a metal detector if you have a concrete or steel septic tank. It is important to perform regular septic tank maintenance on fiberglass and plastic tanks because they usually last 20 years.

1. Find Your Main Sewer Drain Line

Your main city sewer drain line will most likely be found in a basement, garage, or crawl space. Look for a pipe with a screw cap on top and a notched or square knob at the top that is about four inches in diameter. Some houses have an indoor sewage line cleanout point, while others may be found outdoors. Mark your main sewer pipe drain pipe line's location on the exterior of your home. 

A septic tank drain field drains sewage from a home's septic tank into the ground. Pipes are buried underground and connected to the main sewer line. In this way, sewage is prevented from entering the public water supply. The air that fills the concrete tank of a septic tank must be vented just like the vent pipe of a hot water heater. 

Ideally, you should contact your homeowners' association or sewage company if you live in a planned community. Furthermore, if the property is located in a residential zone, you may need to get local governmental approval before digging.

County health departments will keep public records of where household septic tanks and their drainfield are located and include septic maps, so if there is a problem, you can get help from the county. In some states, sellers have to disclose whether the house has a septic system or not. In other areas, local drainage laws may require testing of your soil before you buy a property.

2. Determine Septic Tank Material

Clay, precast concrete tanks, plastic, steel corrugated polyethylene, and plastic small-b pipes can all be used in septic systems. The cheapest septic tank is made of corrugated polyethylene, large enough to hold the solids that are not absorbed by the soil. Unlike a septic tank, oil tanks are typically made completely out of iron or steel and are easily found while metal detecting. 

A plastic SSP septic tank costs more but is cheaper in the long run because it doesn't clog up as easily. These tanks have septic tank lids made of heavy-duty plastic that are located just a foot or two beneath the soil. 

Size of Septic Tank

What type of soil you have in your yard and how quickly water passes through your septic tank determine its size. Generally, a one-bedroom house will need a 400-gallon septic system, while a four-bedroom house would need at least 1,200 gallons. For every 100 feet you add to your home; you need to increase the size of your septic system by 25 percent.

Refer to the public records mentioned earlier for details on the type, size, and septic tank components you have installed.

3. Septic System Location

Your septic tank must be installed at least 15 feet away from your home's foundation to prevent problems with soil contamination. It should also be 2-3 feet below the ground level for easy access and maintenance. Some codes allow you to go as deep as 50 feet underground (or more), but we recommend keeping the lid accessible at all times.

Septic Tank Materials

Iron, concrete, and fiberglass are some of the materials that can be used for septic tanks, depending on their design and purpose. The most common type is a corrugated metal construction which works fine with properly sized access covers.

  • Concrete - A concrete septic tank is the most durable and generally last 40 years or more. Compared to fiberglass models, they cost about three times as much and can handle both wastewater and rainwater. 
  • Steel - Steel septic tanks are relatively inexpensive and can be used for both wastewater and rainwater. Their lifespan is usually 20-25 years.
  • Fiberglass - Fiberglass septic tanks are lightweight and easily installed. Their lifespan is usually 20-25 years.
  • Plastic - Plastic septic tanks are relatively inexpensive and can be used for both wastewater and rainwater. Their lifespan is usually 20-25 years.

Which Septic Tanks Can I Find With a Metal Detector?

While there is no metal detector specifically designed to detect septic systems or any other underground features, these devices can help you pinpoint your septic tanks location in several different ways. 

Metal detectors can detect concrete and steel tanks, but not plastic or fiberglass tanks. This is because the metal detectors can detect steel and the rebar used as reinforcement bars for concrete tanks. Locating your old septic tank location is important if you plan to install a new tank.

If you can determine that your septic tank is either steel or concrete, locating it with a metal detector shouldn't be too difficult. 

With a Metal Detector, Mark the areas of the highest signal strength as you go. 

To find your septic pipes and septic tank, refer to the marked area on the exterior of your home. Septic tanks are typically installed around 10-25 feet from your home. From this mark, measure out at least 10 feet and begin to sweep this area with your metal detector. When detecting, you may find multiple areas that have high readings. There is a possibility that this may be the case if you have an oil tank in your home. 

When searching for a septic tank with a metal detector, having a helper present will make things much easier. Do a thorough search of areas where you believe there may be one if you do not have a partner available. Depending on how long it takes for this process to be completed, you may have to wait for a while. 

The public records from the septic tank installation for your specific tank can also be consulted. Most records will include a diagram of the installation that will show the location of the tanks. 

More advanced tools used by professionals include a metal detector with magnetic locator abilities. This type of tool can differentiate between ferrous, non-ferrous, and conductive metals - essentially telling technicians exactly what materials lie below. By using this type of tool, locating an underground storage tank should be easier and faster than with the first method.

What Type of Metal Detector Do I Use to Find a Septic Tank?

There is no type of metal detector specifically designed to detect an underground septic tank (or any underground features). If your septic tank is made from either steel or concrete, finding it with a metal detector isn't too difficult because these types of detectors can detect those materials. 

To find your underground tank, most metal detectors will do the job. The Bounty Hunter Tracker 4 is an ideal metal detector to use for this job. 

4. Search Perpendicularly, Using the Same Method

Once you've exhausted the search area in one direction, sweep across it perpendicularly, and 

mark areas of the highest signal strength. Sweep a perpendicular area between 10 and 25 feet away from your home. Repeat for all areas with increased signal strength.

In some cases, your septic tank may be equipped with a riser. A septic tank riser is a pipe made of either plastic, fiberglass, or concrete that serves as a ladder to access an individual's septic tank. It creates a vertical passage for easy access for septic tank inspection and pumping out. The riser is topped with a septic tank cover and makes for easy locating. 

5. Mark The Location For Future Maintenance

Perform the original search method again to confirm the results. Using both methods should produce consistent results, but it's always best to double-check. 

Mark the location of your septic tank, ideally the tank's perimeter, with wooden markers, or if you need to do a shallow excavation to ensure you have the right location, dig a small hole around the exact location you identified. It's crucial to mark the location in case of future problems or maintenance like septic tank pumping. 

Regular drain cleaning can reduce the chances of your septic tank filling up. Over time, hair and other debris can build up in your drain. Despite not being visible to the naked eye, it can cause a backup when your sink or shower no longer drains. Clogs are also possible if foreign objects get into the pipes through your garburator or sink.

The only definitive way to locate the septic tank is to excavate where you've narrowed it down. To do this, dig a small hole around your estimated location of the septic tank, and try using a metal detector (the smaller shovels are for digging into the side of hills). A septic lid can be between 4" (10 cm) to 4' (1.2 m) below the surface.

If you intend on excavating near or around your septic tank, be sure that you have obtained all necessary permits before doing any work in the area. 

How Do I Find a Fiberglass or Plastic Septic Tank?

Fiberglass and plastic septic tanks can't be located with metal detectors. This is because these materials are non-metallic, so that they won't set off the detectors. In some cases, these may come with metal lids, typically if a riser is installed.

The best way to find fiberglass or plastic septic tanks is to probe the ground with a metal probe called a soil probe. Plastic or fiberglass septic tanks are generally not too deep; typically, you will find your buried septic tank just one to two feet deep. 

Soil probes allow you to easily probe the soil without creating a lot of damage to your yard. 

Probe gently in the same area discussed earlier. Start from the sewer line marking on the exterior of your home, working outward. After only a few gentle probes, you may find your septic tank. 

If you're still having trouble finding your fiberglass or plastic septic tank, dig a small hole and check for any visible signs of the tank lid. If the lid is broken and not flush to the ground, it's probably a septic tank. Ensure that there aren't any utility lines running through where you plan on digging before proceeding with any excavating work. 

Locating a septic tank or septic tank lid of either type is done with a visual inspection of the ground after you've narrowed down where it might be. You can use shovels to go around the area and dig slightly into the side of hills to make locating your septic tank easier.

Frequently Asked Questions

The following are some of the most commonly asked questions about septic tanks and where they can be found. 

How Do I Find Out Where My Septic Tank Is Located?

Septic tanks are generally installed around 10 to 25 feet away from the building they are attached to. They can be installed in between, but this is not recommended because it's too close to the property line, and there will be difficulties discharging wastewater onto the property of your neighbor.

Finding where your septic tank is located can be done with a metal detector if you have a concrete or steel septic tank. You will need to gently probe the soil beneath your fiberglass or plastic tank if you have one of those.

What If I Still Can't Find My Septic Tank?

Have difficulty locating your septic tank? Call an expert. Check with your local health department if you cannot locate it yourself. If all else fails, call a septic service company; they should be able to find and fix any tank within a day or two, depending on the size of your property.

If you've used a metal detector or the probing method to locate your septic tank and still can't find it, you should contact a local septic service. They should be able to locate septic tanks within a day or two, depending on the size of your property.

With septic services, ground-penetrating radar (GPR) can be utilized to locate and define the limits of septic leach fields and drain lines.

How Do You Find a Septic Tank In an Old House?

In older homes, plumbing is often under the house. A septic tank can also be harder to locate in older homes because its location was not documented when the home was built. In older homes, septic tanks are usually located between ten to 25 feet away from the home. 

People who are trying to find out how to locate a septic tank in an old house should contact their local health department. A plumber can be found by searching online or asking around at various hardware stores if all else fails.

Are Septic Tank Locations Public Record?

Contact your local health department or check online for your area's specific policy to find more information on your home's septic tank. However, only the septic tank owner will have access to its specific location from these documents without an additional court order.

Septic tanks are a public record. Anyone can request a record of a septic tank by going to their local health department. There, the septic tank location could be found in the department's records. 

Is it possible to have a septic tank without a leach field?

A leach field is an open surface where wastewater trickles down through dirt and rock to rest in the groundwater table. After wastewater leaves your home's plumbing system, it enters the septic tank for initial treatment and then drains into the leach field via pipes or hoses. 

Some people opt to use leach fields even if their property doesn't suit them - like when they live on rocky terrain unsuited for this kind of drainage system - but can still install a septic tank without one if necessary.

Instead of a leach field, the wastewater, in this case, simply drains through an additional pipe to run directly into a nearby body of water.

Although it's possible to have a septic tank without a leach field, doing so poses some risks to the environment, which is why most homeowners don't choose this option.

Not only will installing a septic tank without a leach field mean more wastewater in the local water supply, but it also requires you to be very involved with maintaining your own waste disposal system - much more accountable than if there were already an existing leach field in place.

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