Troubleshooting: Check for Hydraulic Overloading

If a homeowner calls about surfacing effluent or an onsite system backing up into the house, one of the first things to check for is too much water use for system capacity

Troubleshooting: Check for Hydraulic Overloading

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I continually get questions about why systems fail and questions about the cause of certain system problems. When you are called to a site where the system is struggling, your first step in finding a solution is to identify the cause of the problem. As you all know, this is sometimes a lot harder than it appears. I will spend a little time going through ways to troubleshoot systems of different types, going over what to look for, and — when possible — giving potential solutions. I did this a couple years ago as some of you may recall, and it led to a lot of good discussion about the causes, identifying them and finding solutions.

Troubleshooting a system starts with communicating with the homeowner. The more you learn about their water use and system use habits, the sooner you can home in on the problem. In addition, constant communication with the homeowner about what you are doing and why you are doing it will cut down on any misunderstandings about your recommendations and ultimately the services you provide and they pay for. There is nothing that creates more problems with homeowners than a lack of understanding what you as the service provider are doing and what is leading you to the conclusion — especially if that conclusion is going to result in the homeowner spending a lot of money on repairs or replacement. There is obviously a problem or you would not be there, but homeowners are just like us: hoping that the fix is easy and, above all, cheap. As we all know, this is often not the case.

When the troubleshooting call is due to surfacing effluent in the drainfield area or a backup into the house from a full system, discussion with the homeowner about what water use appliances are being used, how many residents are in the house, and any small-business activities taking place can go a long way to determining whether the system is being hydraulically overloaded simply from using too much water. Many homeowners, particularly if they have not lived with a septic system before, do not understand or realize that their system has a finite or limited capacity to accept what they want to put into it.

If you are uncertain about what questions to ask the homeowner, there are numerous pamphlets and brochures available through the EPA, state Extension specialists and organizations such as NOWRA - National Onsite Wastewater Recycling Association and National Association of Wastewater Technicians.

Based on their answers about water use, if you feel there is a good possibility that the system is overloaded, I suggest putting in a water meter for a period of time to measure actual use occurring in the home. One of my early troubleshooting experiences involved looking at a system serving a three-bedroom house with an estimated flow of 450 gallons per day. The homeowner was adamant that they could not be using more than that amount of water. Homeowners usually underestimate their use by a lot.

In that case, we installed and calibrated the water meter and let it run for a week. When we came back, the actual average daily use was 750 gallons per day. This is 1.6 times the design flow for the system. The homeowners were still not convinced they could ever use that much water; we recalibrated the meter in front of them and left it for another week, and even though they “watched it,” the average was still over 700 gallons a day. We then talked about installing low water use fixtures and enlarging the system to accommodate actual flow.  

About the author 
Jim Anderson 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

This article is part of a series on troubleshooting onsite systems:


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