All sewage backflow fits into one (or both) of two categories:  its either your own sewage, or someone else’s sewage. The difference is important because it determines how disgusting the problem is, and who pays for the damages.

There are six to eight different types of sewer systems which could be serving your property. These would include gravity flow to a public sewer system, septic tank with gravity drainfield, septic tank with pressurized drainfield distribution, STEP system, grinder pump, and vacuum sewer. If you expect to perform any troubleshooting or repairs, then you need to know which type you have. You can research these systems online. If you have one of these types, then there is a possibility that the problem is located in components which are your responsibility to maintain. You need to know which part of the system you are responsible for maintaining, and which part is maintained by the downstream entity (if any). Otherwise, you may need to call the appropriate agency or a plumber to determine this.
If your structure is connected to a public sewer main pipe, then the public system is usually located in the street in front of your structure, or the alley (or easement) behind it. Wastewater is supposed to only flow away from your structure, and come out at the downstream end of the collection system. However, physics always governs the flow of water. It is possible that the sewer pipe is too small for the amount of flow. This may be the case if too many customers have been added to the pipe, if rainfall is draining into the pipe, or if groundwater is leaking into the pipe from underground. Search online for the closest rain gage or rainfall records to determine whether there is a correlation between rainfall and sewage backflow. It is possible that the sewer pipe is either plugged by grease, plugged by tree roots, or entirely collapsed. It is possible that a backwater valve (sewer check-valve) has failed, or perhaps it was never installed in the first place. It is also possible that sewage is backing up because a downstream sewage pump has become plugged, the motor burned out, or the power failed. All of these circumstances leave evidence which can be documented. You will need to obtain the documentation.

Try This:

If you are familiar with your wastewater system, then you can attempt some trouble-shooting yourself.  You should have performed some due diligence prior to purchasing, renting, or occupying the structure so that you understand the basics about how your wastewater system operates.  If  you are not willing to perform some minimal amount of research and take responsibility for your own actions and your own safety, then stop right here and call a plumber.

If it is safe to do so, turn off the water service to the structure, and document how you did that with photographs.  Does that reduce or eliminate the problem?

Locate your cleanout caps and remove them (unless the sewer is under pressure).  With enough light, you should be able to see all the way into the sewer pipe.  A gravity collection system should not have any standing water in the vertical portion of an exterior cleanout riser.  Standing water in the cleanout is usually an indication that the problem is downstream of the cleanout.  If you have standing water in your exterior cleanout, then drop dye tablets into the cleanout with photographic documentation. Use a sewer tracing dye which is non-toxic and bio-degradable. If you don’t have a sewer tracing dye, then perhaps use food coloring or tumeric. There should never be any reverse-flow.  If you then see dye-colored water inside of your structure, then you have backflow of sewage which you should document with photographs for proof. It would be most useful if you have photographs before and after placing the dye, with a submerged white card to show the color better.

If the sewage has already flooded an area, then you should obtain samples and dimensions from the flooded area. Find some large glass jars to obtain samples.  More samples are better. Samples can be tested at a water quality lab to show that the water has the characteristics of municipal wastewater, and therefore it was not coming from your own roof drains. Research “wastewater sampling procedures” online and make sure you do it correctly or it will not count as evidence. You will probably want to put the samples on ice, or refrigerate the samples. Make sure you do all of this this safely. If the flooded area is not ventilated, then do not enter that area.

After the flooding, you should estimate the volume of sewage within the flooded area. Obtain the dimensions. Wastewater will usually leave a visible high-water mark on the walls and furniture, so this step can wait until later. Measure or estimate the length, width, and depth of the flooded volume. Photograph the dimensions on the measuring tape while taking all measurements. More photographs are better.

You may strongly suspect that the sewer is coming from the sewer main out in the street, but can you prove it?  The way you will prove it is by proving that the volume of wastewater greatly exceeded any amount which could possibly come from your own plumbing, and by proving that the water is in fact sewage.

Resources for Further Research

Read your homeowner’s insurance policy to determine whether it covers flooding from the public sewer system. Also, check out the following:

  • American Waterworks Association (AWWA) Standard G520 Wastewater Collection System Operation and Management.