Determining the location of a septic tank is the first step of pumping a septic tank. The best-case scenario is for either the homeowner, property manager, or resident to know the location of the tank. [I have yet to get a copy of an accurate Plat or Permit drawing.] If the location of the septic tank is unknown, septic tank location can be accomplished with a flashlight, and a probing rod. A flashlight is used for finding the drain line in a crawl space. A probing rod, the yellow and blue “T Handled” object in the picture below, is used to penetrate beneath the ground to probe for the presence of a septic tank.

However, sometimes the ground can be too hard to get the probing rod to a meaningful depth and exploratory excavation must commence, unless one has electronic tank location tools [these tools will be covered in later blog posts].

 The remainder of this article will address three conditions under which location was necessary and the methods by which septic tank location was achieved.

 Easy – All Fill Dirt

 For the property pictured below, I had access to a permit plan drawing. The permit plan showed two tanks in one version, and three tanks in another revision. Neither of the plan drawings accurately depicted what was installed in the ground. This is why septic tank location must be confirmed physically prior to excavation.

The property was beautifully landscaped and the entire yard was sod on top of nice fill dirt. Fill dirt has been excavated and replaced and is easily penetrated by the probing rod. We were able to quickly locate one tank to the side of the house [but not a second tank which should have been run in series according to the drawing], and a tank in the front yard [which was not even present on the plan drawings. Here are photos of the tank in the front yard and the side yard:

 Medium – Some Fill Dirt


For the property pictured below, I knew where the drain line exited the house and I only needed to probe the yard. The yard had no fill dirt except over the septic tank. So, I only needed to probe the topsoil to look for ground which was easily penetrated by the probing rod. The tank was easy to find within the small section of ground which was easily penetrated by the probing rod.

Hard – Never Pumped and Any Fill Dirt Settled for roughly 60 years


For the property pictured below, the entire backyard was hard clay with granite. The dirt over the tank was the hardest dirt seen by one of our team members [a master plumber with over 40 years of experience]. The ground could not be reliably penetrated more than 2 inches with the probing rod more than 2 feet away from the foundation of the house.

I was able to locate the drain line exiting the house and into the yard [this was not a straight line from the exit seen under the house]. Once the drain line was marked, we received permission from the homeowner to excavate the yard in order to locate the septic tank. We followed the drain line out and located the septic tank on our first deep hole. This would not have been possible without a deep hole, and this process was impractical with hand tools. The post hole digger would have kept us at the property all day. Luckily our excavator made short work of the location process.