Jim Anderson, Ph.D.
Where I live, the majority of houses have a basement at varying levels below finished grade. From a septic system perspective, it means that there is often a sewer ejector pump in a sump in the basement to handle washroom and sometimes toilet waste. These basements also have varying degrees of wetness, which is solved with drain tile installed below and next to the footings on the inside of the basement walls below the floor.
Water collected also drains to a sump and then is delivered by a pump back to the outside and hopefully far enough away from the foundation to avoid constantly recycling the same water. From my perspective, a better solution is to install the drain tile on the outside below and next to the footings, with the water discharged by gravity away from the house. But that is probably a discussion for a different audience.
When troubleshooting a system, if there are footing drains, it’s important to make sure water from those drains is not entering the system. Depending on soil type and location, the amount of water delivered through footing drains can quickly hydraulically overload a septic system. Remember, our systems have finite capacity and footing drain flows can exceed the daily sewage flows themselves. This cannot go on very long before the system either surfaces or backs up.
As I like to say sometimes: “In the old days when I started in the industry,” you would look at the laundry sump and see that there were two lines coming in — one was the sewer line and the other from the footing drains. If the installer was aware that having all the clear drain water going to the septic system was not a good plan, the pump in the sump would have a bypass valve that would be turned one way while doing laundry and the other to drain around the foundation.
While this is better than no valve at all, this still is not a good plan. First, it relies on a homeowner changing the valve, and we all know how well that works. And second, there is always a time when there will be a combination of sewage and clean water delivered either to the septic, the ditch, or the neighbors’ property, depending on where the outlet to the pump is in the yard.
The solution to this problem is to install a separate sealed sump and pump that discharges to the septic system. If the sumps and systems are separate, the sealed sump should be closely inspected to determine if it has an intact bottom and no other cracks, especially around where the sewage pipe enters the sump. The sewage sump can still collect some footing drain water through these cracks and deliver that water to septic system. A way to check this in dry times is to fill the sump with water and observe if there is any drop in water level over 10 to 30 minutes. If the water drops, the sump should be repaired or replaced to make sure there is not a connection.
If there are two separate systems, you should check where the discharge point of the clean footing water is relative to the drainfield or other parts of the system. If the discharge is on top of or near the drainfield or other components, it should be rerouted to ensure the water is not interfering with drainfield operation.
About the author: Jim Anderson, Ph.D., is connected with the University of Minnesota onsite wastewater treatment program and is an emeritus professor in the university’s Department of Soil, Water and Climate. Send him questions about septic system maintenance and operation by sending an email to kim.peterson@colepublishing.com.
