how to find a septic tank

How to Find The Septic Tank
Step by step how to locate septic tanks for inspection or septic tank pumping

POST a QUESTION or COMMENT about all methods for locating a septic tank, drywell, or cesspool as well as other septic system components such as the D-box and septic soakaway bed, leaching field, or drainfield.

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Septic tank location guide:

This document provides suggestions and procedures for finding a septic tank.

This very detailed article series (see links listed at the ARTICLE INDEX the bottom of this article or below) tells how to locate a septic tank or other buried site components such as the distribution box, drainfield, or a cesspool or drywell when it's placement is not already known or when the location of the septic tank is not visually obvious.

This guide explains the septic tank search process and lists sources of information about septic tank location. We describe who may know where buried components are located at the site, how to inspect the site, and what mistakes to watch for in assuming that the information you see, read, or are told is absolutely correct.

We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

How to Find the Septic Tank, Cesspool, Drywell, D-box, or Drainfield

Photo of septic tank sludge and scum layer being broken up prior to septic tank cleanout.

Beginning here and in a series of detailed procedures we explain various methods to locate buried onsite wastewater disposal system components: the sewer line or main drain, septic tank, septic tank cleanout openings, distribution box, septic drainfield, and related site components.

If you prefer to watch a video on how we figure out where a septic tank could or could not be located,

see SEPTIC VIDEOS.

Also see SEPTIC DRAINFIELD LOCATION.

When the septic tank needs to be pumped, a regular maintenance task, the cost of that service will be less if the property owner found the septic tank location and perhaps even uncovered the septic tank pumping access cover.

Other reasons to find the septic tank include inspecting and testing septic systems when buying a home or for safety, to assure that the septic tank cover is in good condition.

If you don't know whether your property even has a septic tank, your building could be connected to a municipal sewer main. To figure this out,

see SEPTIC or SEWER CONNECTION?

Safety Warnings for People Looking for the Septic Tank

Watch Out: Septic System Warnings: Here are a few conditions that may be confusing or dangerous and which you should keep in mind:

Beware of old, collapsing septic systems
falling into a cesspool or septic tank is likely to be fatal. Watch out for evidence of subsidence or sinking soil, rusted-through steel septic tank covers, home-made wooden or flimsy tank covers, or home made cesspools and drywells which risk collapse.

Dig or probe with great care and do not work alone. More guidance about safety when working on or around septic systems can be read

at SEPTIC & CESSPOOL SAFETY. [Thanks to Donica Ben for reminding us that there are other potential hazards such as striking a buried electrical wire.]

Multiple main drains?
At a large property or a property with plumbing fixtures at widely separated portions of a building, the builder may have constructed more than one septic system, or waste lines could leave the building from more than one location even if they go to the same septic system.

This would be uncommon in a modern home. But at a property which has been expanded, say to add an apartment at a far end from where all of the other building plumbing exists, this is a possibility to keep in mind.

Consider the age of the building, the complexity of its layout, and the history of additions of baths or kitchens at widely separated areas as a clue suggesting that more than one septic system or waste line may be present.

Separate drywells?
On properties which have septic drain fields (absorption systems) of limited capacity to absorb wastewater, or for reasons of simple convenience in running drain lines, the building gray water from laundry or even sinks and showers may be connected to a separate drywell which is not part of the main septic system.

In the photo above showing a washing machine in the foreground and the main house waste line in the basement left corner in the background, you might wonder if the washer is connected to a separate drywell. The washing machine in the photo is obviously below the level at which the main drain leaves the house in the distance. What simplifies finding the septic tank in the case of this photo is that there is only one large diameter waste drain leaving the house.

Main drains are bigger
The main house drain lines will be comparatively large in diameter, a minimum of 4" (obsolete) and possibly 6" in diameter. Individual sink or shower drains may be 1.5" or 2" in diameter. So if you can see exposed plumbing, just find the area below a building toilet and follow that drain.

Toilets must be connected to a septic system, even if other building fixtures connect to a separate drywell. Right now we're looking for the septic tank, not a drywell.

Ask Those Who May Already Know the Septic Tank Location

Ask the prior owner: the Building's Most Recent Owner May Know the Septic Tank Location

When the location of a septic tank is not visually obvious ask the building's most-recent owner the location of the septic tank. But beware, people can be mistaken, or may have forgotten, or may have never known where their septic tank is buried.

When a building owner does not know where the septic tank is located that is itself useful information. In that case, if we know how long the owner has been in the building, we know it has probably been been at least that long since the septic tank was last pumped.

When a septic tank has not been pumped on schedulethen even before inspecting the system we must be more pessimistic about the condition of the system and in particular, about the remaining life of the drainfield.

An building owner who has had the septic tank cleaned before is likely to know just where it is located. In an older home an owner may have a drawing of the tank location or may have drawn measurements to the septic tank on a garage or basement wall, perhaps near the main waste line outlet.

Watch out: sometimes the a building owner or prior owner does not really know the tank location, may have forgotten, or have become confused. We conducted a large excavation at the spot where a homeowner told us, with great conviction, where a buried component was located. Ultimately we discovered the component more than 50 feet away.

When we confronted the owner with this confusing data he remembered and explained: "Yeah, I never actually saw it, that's where the previous owner told me he thought it was."

See details at VISUAL CLUES LOCATE the SEPTIC TANK

and

details at SEPTIC TANK PUMPING SCHEDULE

Ask local septic tank pumping companies for help: local septic servicers may know tank location

In addition to asking building owners, if the age of the home means that the septic system has been present for four years or more, it is possible that even though a current owner may not know the septic tank location, a local septic pumping company might.

It's worth a call to each local septic pumper to ask if they've serviced the property. WARNING: don't rush to let a service company or local excavator come out to dig up the yard - it may not be necessary and it may involve unnecessary costs.

Look For Records of Septic Tank Location

PHOTO of how to record measurements to locate the septic tank cleanout cover.

Most often homeowners who have ever had a septic tank installed or serviced record a sketch showing measurements to the septic tank from some visible property feature such as a corner of the building.

At RECORD SEPTIC TANK LOCATION we describe the procedure for making those measurements and the required sketch.

Look in the building basement or crawl space for the point at which the main building drain exits the building.

See FIND MAIN WASTE LINE EXIT - start finding the septic tank by finding where the waste line exits the building for details.

While a septic drain line can turn around on a property and the direction of the exit drain pipe is not a guarantee, often it points right to a septic tank that is close to the building.

Look in this same area in the building for a sketch, sometimes drawn right on the building wall or rim-joist, marking distances to the septic tank and its cleanout cover.

See SEPTIC TANK LOCATION SKETCH - how to make a sketch showing a septic tank, D-box, or drainfield location

Check with local septic tank service companies. If the building is not new, it is possible (we wish we could say likely) that prior owners had the septic tank cleaned or repaired from time to time. If so the company may have notes on where the tank is located.

Just Where to Look for The Septic Tank

Unknown septic tank location procedure: This article tells us how to locate a septic tank when it's placement is not already known or when the location of the septic tank is not visually obvious. We include example photographs from across the U.S. and from other countries illustrating visual clues for finding a septic tank when its location is unknown.

When a septic tank needs to be pumped, a regular maintenance task, the cost of that service will be less if the property owner found the septic tank location and perhaps even uncovered the septic tank pumping access cover.

Other reasons to find the septic tank include inspecting and testing septic systems when buying a home or for safety, to assure that the septic tank cover is in good condition.

Septic tank location by house drain © D Friedman at InspectApedia.com

Videos showing how to find the septic system, septic tank, & septic drainfield are

at SEPTIC VIDEOS.

Also see SEPTIC DRAINFIELD LOCATION - how to find the leach fields.

Find the main building drain exit point. Often the septic tank is 10 feet away in a straight line from that point. (Not always). Our photo (left) shows a wall vent connected to the main building drain line (too close to a window too). We looked for the septic tank in a straight line away from the house starting in this location.

Start looking close to the house wall - perhaps 4 ft. away (which would be too close for modern standards) or at 10 feet away for a better location.

Septic tanks are often buried close to a building because of the convenience of excavation during original construction, and to avoid unnecessary piping costs to a remote tank.

On occasion, particularly in an un-finished basement or crawl area, you may find a septic locating sketch on paper, folded and stuffed nearby, or a sketch drawn right on the building foundation wall or rim joist.

Septic tank marker © D Friedman at InspectApedia.com

Building codes typically require that the tank be located 10' or more from the building so 4' is a bit close but at some old properties we've found the septic tank right next to the foundation wall of the house.

At 12 feet from the home we found this flat stone in the lawn, marking the septic tank cleanout opening.

Watch out: the septic tank may nevertheless be located distant from a building if site conditions such as space, rock, proximity to a well or lake prevent its installation nearby.

Our photo (below left) shows where we spotted a septic system cover downhill from a hilltop restaurant in Molde, Norway. The city, Molde, is visible in the upper portion of the photo.

Septic tank cover Molde Norway © D Friedman at InspectApedia.com

Look downhill from the building main drain if there is no septic pump system installed.
Look at the site itself for obstructions that might have forced the excavator to put the tank into a more remote location, such as large rocks and boulders, streams, property boundaries, wells, similar site features.
Look for subsidence in a round or rectangular pattern that may mark the septic tank location.
Look for bald spots where there is no grass growth or brown grass that's dried out - - marking a shallow-buried septic tank top
Look for green grass that may mark a septic tank that is backing up and leaking.
See SEPTIC TANK GRASS

Snow melt over septic tank © D Friedman at InspectApedia.com

The location of this septic tank was downhill from a home located close to a lake in Grand Marais in northern Minnesota.
If you are looking for septic system components at a building close to a lake or other waterway, the tank may be downhill from the building so that the building does not have to pump wastewater to the septic tank.

But expect to find a pumping chamber at the septic tank that sends effluent to a drainfield that will be located uphill and well away from the waterway.

That electrical box sticking up in the yard pointed out the pumping station for this septic tank, and the rectangular growth over the tank was a rather compelling clue as well.

A septic tank cleanout and pumping station access covers were located within that growth.

Snow melt over septic tank © D Friedman at InspectApedia.com

If there is snow-cover look for a round or rectangular area of thinner snow or melted snow; bacterial action and warm wastewater often mean a higher temperature at the septic tank.
Details are at SEPTIC TANK SNOWMELT.

Our photo (above-left) illustrates melting of light snow cover above septic tank access covers at a property in northern Maine.
In the photo at page top we saw a very rocky hill with thin soil, making the probable septic tank location down in the distant, flat, lower yard.
The septic tank was found to the left of the garage just at the bottom of the hill. The small size of the available area also means that the owner chose to install a pair of high capacity drywells to absorb septic effluent instead of a more space-hungry conventional drainfield.

Look for a 6" or 8" septic cleanout or access pipe such as the one shown in our photo . This septic system is located in Marana, outside Tucson, Arizona. The terrain is not only hot and arid, but also flat - not much worry about having to look "downhill" from the building.

Septic cleanout access © D Friedman at InspectApedia.com

OurSEPTIC VIDEOS show how you can walk a property to find areas that are likely or unlikely to contain the septic tank or drainfield. Locations such as dense mature trees close together, or right next to a drinking water well are not where we'd expect to find the septic tank.

Exploratory Digging to Find the Septic Tank

Our photograph shows a round steel septic tank cover right at ground level and just about 30 inches from the house foundation wall. You can see that if you were jamming a probe into the soil over a cover like this one, you'd easily puncture and ruin it.

(When this septic tank rusts through you may see sewage leaking into the building through the foundation wall.)

Dig or probe very gently in the area where you think the tank cover is located -

Watch out: beware of collapsing tank covers and do not work alone - falling in is likely to be fatal - read my Safety Suggestions article above before beginning this work.

What to do if We Can't Find the Septic Tank?

What if there are no visual clues of tank location and we can't easily find it outside?

The last resort is a bigger digging project which we describe next.

Cross Trenching: At the building wall where the waste line exits, dig a small trench across the suspected pipe location going down until you find the pipe. Note its apparent direction. Move out 3-4 ft. in that direction and dig again.

In other words, follow the pipe by excavating small test trenches across the suspected pipe direction until it leads you to the tank. This is what an excavator does with a backhoe if they can't find the tank by other means.

Tanks may be distant: Beware, while the septic tank is often found close to the building (where it's easier to bury the tank and for other technical reasons), site conditions can make it necessary to locate a tank at quite a distance away.

How to Use a Simple Plumbing Snake or Using Electronic Equipment to Find the Septic Tank

Special equipment using a plumbing snake and electronic sensors and other methods are available when needed.

By inserting the plumbing snake into the main building drain and pushing it until it stops dead, the snake end has usually hit the septic tank inlet baffle. From this procedure we know the maximum distance from the building drain to the septic tank. We say maximum distance because we don't know for sure that the drain line runs straight to the tank.

A combination of conductive metal snake in the plumbing drain and electronic equipment can trace the routing of a drain line precisely as well as locating the inlet to the septic tank. Details are

at SEPTIC TANK LOCATING EQUIPMENT - plumbing snakes, electronic pipe tracing equipment, etc.

Watch out: well not always precisely. Radio transmitter and similar electronic devices that are used to pinpoint buried pipes can be thrown off a bit if there are other metal pipes buried nearby, crossing or in parallel to the pipeline of interest.

Metal septic tanks can be found at their buried location using a metal detector.

When & How to Dig or Excavate to Find the Septic Tank

PHOTO of excavation during septic system repairs - knowning the septic tank location can avoid tank damage during repair work and can speed servicing the tank and cut tank pumping cost.

The photo shows excavation during septic system repairs - this is not the best way to find a septic tank. Knowing the septic tank location can avoid tank damage during repair work, and it will save on septic tank pumping cost since you won't be paying an excavator to find and expose the tank cover.

Avoid "finding" the septic tank by using a backhoe unless the operator is very skilled and careful. At our first home with a septic tank the backhoe operator "found" the septic tank by driving over it and crushing it, leading to a costly repair.

If you have to excavate, or if you are excavating to confirm the septic tank location and to find its cleanout covers then heed this warning:

Watch out: for unsafe septic tank covers that can collapse - falling into a septic tank is usually fatal. Don't use a heavy iron wrecking bar to "probe" for the septic tank by jamming it aggressively into the soil.

That's a good way to punch a hole in a steel septic tank lid, cause a tank cover to collapse,or to burst a buried pipe or break a toe.

See SEPTIC TANK COVERS - important safety concerns.

Also see SEPTIC TANK DEPTH - how deep might the septic tank be buried anyway?

How We Walk the Site to Recognize Where a Septic Tank Could or Would Not be Located

If no record of the septic tank location is at hand, an experienced septic pumper can generally guess where the tank is likely to be by inspection of the property, or s/he can locate the tank by careful probing. Details are
at WHERE TO LOOK for the SEPTIC TANK - what are the reasonable locations where we could look for a septic tank

and then

at VISUAL CLUES LOCATE the SEPTIC TANK - what can we see that tells us septic tank locatio. A summary is below:

We do not normally expect to find a septic tank located:

At a great distance from the building - such locations involve extra cost that people want to avoid
Right next to or close to the well - such locations are unsanitary and illegal
See details at CLEARANCE DISTANCES, SEPTIC SYSTEM
On top of visible solid rock or rock outcroppings or where soil is very thin over rock or shale
At or close to the edges of the property -
see DISTANCE TO SEPTIC TANK - what are the clearance distances required between a septic tank and other things?
In the midst of a dense growth of mature trees - how would the backhoe have gotten in there to dig a hole for the septic tank
Downhill from the likely or apparent drainfield location - but a common exceptions include septic tanks that use an effluent pump system to lift effluent to a mound or raised bed septic system, or septic tanks that are located close to but down hill from a building close to a lake or stream.
Such installations may place the septic tank downhill from the building so that building drainage does not require a sewage pump; but in order to get the septic drainfield an acceptable distance from the lake or waterway the system may have included an effluent pumping station: so the tank is downhill but the drainfield may be uphill from the position of the building itself.

We often expect to find a septic tank located

Within 10-20 feet from the building. During building construction it is often convenient to excavate for both the foundation and the septic tank hole at the same time. And keeping the tank close (but not too close) to the structure saves on plumbing costs.
Also see POSSIBLE SEPTIC TANK LOCATIONS - finding a septic tank includes ruling in and out where it might be

When the septic tank has been located, note if it is installed with improper clearances from other site features such as a private well, and inform the owner accordingly. The measurement procedure to record the septic tank cleanout cover location is

at RECORD SEPTIC TANK LOCATION

Reader Q&A - also see the FAQs series linked-to below

It would be no surprise to find an abandoned septic tank on a very old property.

Watch out: The real Hazard is that the cover is on safe and someone Falls in and, depend on what's in the septic tank face is a quick and nasty death. Safe thing is to fill it

So yeah. I live in a house that is over a hundred years old. We started having some issues with standing water in the backyard a few weeks ago and just recently started to investigate.

Both my neighbor and my dad thought we were hooked up completely to the main sewer system of the town but when we dug into the ground of the backyard we came across a concrete structure to which only our kitchen sink drains. It seems as though the side of the concrete structure had degraded creating a hole through which this nasty smelling water is coming out of.

Is it possible that the mystery concrete structure is a septic tank?

Our plan is to uncover the rest of the structure to find the extent of its size and to cut down labor costs from the plumber ;)

Alicia

That could be a round septic tank access cover. I can't say in part because we know nothing about your property, site, age, history, plumbing, nor the sie of the stone-like item in your photo (It doesn't look prefectly-round but it may be tipped)

Watch out: it sits askew, may be leaking into the septic tank (risking flooding), and worst, if it is not secure over the septic tank top there could be a risk of it moving, tipping, and someone stepping into or falling into the septic tank - a quick fatal event. It needs to be investigated further by an experienced excavator or septic contractor.

Hello. Is this photo a septic tank cover? It is up a hill from my house at a good distance from the house. Otherwise, I fear my septic tank may be underneath my concrete patio.

email to roseh@nc.rr.com

Belinda

Yes it certainly possible that you have found your septic tank.

Watch out: if the condition of the septic tank including its materials of construction and the condition of the cover or any access openings are unknown there is the risk filter cover is unsafe.

Should someone step through or fall through the risk is Serious injury or even a fatality. Therefore it would be smart to keep away from the suspected septic tank location until you have had an excavator expose enough of it to understand whst us there, and its condition.

Watch out: also for a septic failure that is likely if your septic system is one in which no one knew the location of the septic tank.

When no one knows where the septic tank is located to me that suggests that no one has been doing the required regular maintenance of pumping the septic tank. When we never pump the septic tank we shorten the life of the drainfield.

I wanted to plant flowers outside my bedroom window, I stuck my shovel in the ground and hit a solid object only six inches down. Using a probe it appears to be appr. 4x5 ft lrg and only ten feet away from original home and 4 ft away from the addition. Septic??

Certainly, Brian, particularly in older towns.

In fact we have inspected homes in areas where there is municipal sewer but found cases in which

- the home was never connected to the sewer and still is on private septic

and also cases in which

- the home had a septic, was later connected to sewer, but the septic tank was left in place and not properly abandoned - this forming a safety hazard

I have city sewer, is it possible to have an old septic on my property still? There is a heavy thick round piece concrete in the middle of my back yard and I don't know what it is.

Question: does this concrete thing mean we have a septic tank?

Concrete cover probably marks septic tank location (C) InspectApedia.com Jenna

2018/11/04 Jenna said:

First, please excuse my ignorance. Now .We are considering the purchase of a new home

BUT I am completely confused/concerned with the sewer/septic situation. The home is owned by a company and the disclosure is basically worthless.

There are two "covers" on the side of the house. One, concrete, I assumed was a septic? The other looks like a sewer manhole cover. The neighbors home also has the metal "manhole" cover.

So I guess my questions are...does this home have a septic system? Or is it connected to a city system? Isn't this rather close to the house if it is a septic tank?

If not...why does this house and the neighbors (presumably all) have a manhole access in the yard? And are there any precautions/inspections/advice we need before proceeding with this house? THANK YOU!

Reply:

Jenna thank you for asking about how to figure out if a home is connected to public sewer or private septic - it's not an ignorant question; the only ignorant step would be failing to ask.

SEPTIC or SEWER CONNECTION?

will help you figure out the answer.

A call to your city's building or water or sewer department can sometimes close the question immediately: ask if there is public sewer available to homes on your street.

Beyond that:

The square concrete on the ground in your photo looks like a septic tank access port and marks a common and reasonable location for a septic tank near you rhome - but could be something else. It is common for a septic tank to be close to the house, perhaps 10 feet from the foundation.

It should be trivial to simply lift the cover to see what it locates.

If you see into a pool of sewage you know it's a septic tank.

But

Watch out: at any unknown property where there may be a septic tank of unknown condition there's a risk of falling into a tank or even being overcome by fumes.

Never work alone, and never lean over the septic opening, nor step onto a questionable tank cover.

...

Continue reading DISTANCE TO SEPTIC TANK if you are looking for its location, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see SEPTIC TANK LOCATION FAQs questions & answers posted originally at this article

Or see these

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SEPTIC TANK, HOW TO FIND at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to SEPTIC SYSTEMS

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