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How to Find a Septic Tank

By Corey Tournet August 31, 2018

How to Locate a Septic Tank

It is not easy to find a septic tank. The first thing to do is contact the local health/zoning office to see if they have a plan on record.  If the system is fairly new you have a chance, but many states didn’t start keeping records until the 1990’s and even still they are spotty at best.  Even if they do have a drawing on file, it probably will not match exactly what is in the ground, but it should be close.  If you can find out who installed the system they should be able to tell you where to find the septic tank..     

If none of that pans out, then you will want to identify where the sewer main leaves the house.  If you have a basement or crawl space you can look for a 4” black pipe…look where it goes out of the foundation.  If you don’t have a basement/crawl space, or the sewer main is under the foundation, you will have to look for the lowest drain in the house.  This is usually a floor drain in the laundry area and this is generally the area where the pipe will leave the house.   

Once you have an idea where the pipe exits the house you want to go outside to that part of the house and take a ¼” or ½” steel rod about 5’ long (concrete re-bar will work but a stainless steel rod is better because it doesn’t “stick” to soils as much) and start probing the ground next to the foundation until you hit the pipe.  Be careful.  Poke too hard and you could poke a hole in the pipe, particularly if it is older cast iron pipe. 

Once you find it you will want to move further out a few feet at a time to track the pipe until you find the septic tank.  Tanks are usually 10 to 20 feet away from the house.  Once you find the tank you will want to probe around it to get the outline.  Tanks can be round, square or rectangular, but once you know the size you can start digging right in the middle.   

You are trying to find the manhole cover, it could be in the very center, it could be on the inlet side, it could be on the outlet side, there could be 2 or 3 covers, there could be none.  Sad to say there are no standards when it comes to tanks so you get what the manufacturer had at the time.   

Finding the distribution box can be a little easier.  It is usually about 10 to 20 feet away from the tank and sometimes you can spot it just by looking at how the grass is growing.  Often the grass will grow greener over the drainfield lines and if you can see the pattern on the lawn where the lines come together, there it is.  If not you can find the distribution box the same way you found the tank. 

However, it is seldom a snap process, it can be extremely difficult to find the septic tank and distribution box. Many is the homeowner whose yard looks like a minefield by Sunday night, and they still haven’t found the tank or d-box.   

The obstacles you can run into are:

·        Tight clay soils.  Clay can be difficult not only to stick a probe into; it can be tough to pull it back out.  

·        Rocky soils.  You think you hit the tank so you start digging only to find a rock.  And that can happen over and over.   

·        Deep systems.  More than 2 or 3 feet deep can be a real treat to track and dig.  

·        Older systems.  Back in the old days people did what ever they wanted.  Sometimes you will find pipes that seem to twist and turn then disappear into nothing.  Other times you will find something really inventive, like a Volkswagen buried in the yard and being used as a cesspool.  Swear to god, it happens.   

This is why I suggest biting the bullet and hiring a full service contractor to find the septic tank (I say a full service contractor because some pumpers will only pump tanks, they won’t find them).  And often a good contractor can tell where everything is just by the lay of the land.  And if they can’t spot it by eye, they have the tools to find them easier, some even have small radio transmitters that they can flush down the drain and track as it goes through the system.      

And here is another thing, what happens if you do find the septic tank/d-box…what are you going to do after finding it?  Do you have the tools and know-how to replace a missing baffle?  Do you have a line jetter or rooter sitting in the garage? How about that 3,000 gallon pump truck to empty the tank?  Probably not.

Of course once you have the pro find everything, you can mark it (there are small markers you can use to landmark the system) and know where everything is.   

No one likes to spend money on things like locating your septic tank, but put it in perspective: if you had city sewer, you could easily spend $300 per year for sewage treatment.  Over 10 years that would be $3,000.  Spending $200 to $500 to have your system located and maintained is not too bad.  And if you take care of your system, which means pumping the tank every 1 to 3 years, practicing wise water/chemical use, an effluent filter in the tank and a washing machine filter in the house, the cost to maintain your system could drop down to $25 per year.  Not a bad deal when you think about it.   

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