When we conduct workshops or are in the field with other onsite professionals looking at malfunctioning systems, the conversation often turns to the reason septic systems fail. For us, failure is when the system is not operating as it’s designed to; sewage is backing up or surfacing, or effluent is going away, but not being treated properly.

We have been working together for 25 years and we’ve noticed there is usually always more than one thing wrong when we are out troubleshooting a system. We always run through the following potential reasons the system in question is not operating as it should:

1. The homeowner is routinely using more water than the system can handle. Systems are designed to handle a finite amount of water, and in code it is usually expressed in terms of an average per person or a value based on the number of bedrooms in the house. The overuse may just be that the people living in the house use more water than the average 60-70 gallons per person per day. But overuse can also result from leaky and unmaintained fixtures or from other extraneous water sources such as surface runoff or clean water drainlines around foundations that are being routed through the system. The homeowner, after the fact, may increase the load by enlarging the house to accommodate more people or add water-using devices the system was not designed to handle, such as garbage disposals and large showers or tubs.

2. The system has not been properly maintained. The septic tank should be regularly checked and the solids and scum removed before they accumulate to levels that can be detrimental to the soil treatment part of the system. Advanced technologies, such as ATUs and media filters, require increased levels of care. These are often covered in maintenance contracts written upon completion of the system, but not renewed because there have not been problems or when new owners move in. Systems with advanced technologies that are not cared for can represent more of a health and environmental risk than a failed conventional septic drainfield system.

3. Improper design or installation. Here it may be that the system selected or designed does not fit the site and soil characteristics. This can be due to compaction problems in the soil treatment area when the system was installed. It may be the tanks were improperly installed or that good pipe-laying procedures were not followed. Or the designer was unfamiliar or misinterpreted the information provided by the site evaluator.

AND THE WINNER IS ...

In our experience the single largest cause of system failure goes right back to the process of siting and installing, specifically the identification of soil conditions at the site. Mistakes lead to errors in design and installation, resulting in way too many systems having little chance of working right from day one.

Designers and installers need to be familiar with and understand the impact of three soil characteristics: soil texture, soil structure and soil color. Texture and structure are characteristics used to determine the soil sizing factor and the size of the soil treatment area needed. Color can indicate a number of soil conditions. The most prominent is the presence of a seasonally or permanent high water table, even during dry periods. Another is to help identify when the soil has been disturbed and will likely not act like a natural soil of the same texture.

Those familiar with these characteristics recognize other site and landscape factors contribute to selecting the right kind of system and identifying where a system should be placed on the lot. However, we have found that when these soil characteristics are misidentified, there is usually a lack of appreciation by the designers about how they might impact the system. Conversely if texture, structure and color are properly identified, the additional important characteristics are also recognized and factored into the design.

TALK TO INSTALLERS

In our view, site evaluation is the most critical piece to ensure that a system will last long into the future. Installers, in our opinion, are the last line of defense to correct siting and design errors, which is why we maintain that installers need to recognize soil characteristics. Installers in any given area are usually very knowledgeable of changes in soil characteristics due to their vast field experience.

If the installer recognizes major soil characteristics and relates them to the kind of system to be installed, and notes differences when installing the tanks or beginning to excavate trenches, it is time to call out the site evaluator and designer to take a look. Then a decision can be made whether to proceed with the system as designed. We hear a lot of disagreement on this point, but there is no disagreement about who gets the first call from the homeowner when the system doesn’t work. That would be the installer.

This is why we feel strongly that all designers, site evaluators and installers need to have some training in soil identification. We would go one step further and highlight that inspectors and regulators should have that same training to avoid the most frequent cause of system failure.