I was shocked to learn of a state in the middle of our country that has only a seven-year average life on their onsite systems. A state in the southeast averages 15 years for their systems.
Here in Wisconsin, I always tell my customers the average life of an onsite system is between 20 and 25 years. Yes, I see systems as old as 50 and 60 years that are still "functioning." I have also seen systems fail in four. But the average that I see is 20 to 25 years. One summer every system I replaced was exactly 20 years old.
I understand that each of our regions or states have different soil conditions and that plays a big part. But what are some ways we can all add longevity to the systems we install?
Recently, my company was called to troubleshoot a mound system and had to give them the bad news that their mound required a type of recore or rebuild where we have to replace the pipes because the orifices are all plugged. Because the mound was solidly plugged up, it burned out their pump as it was trying to pump out to the mound.
The mound is only seven years old, so the homeowner obviously was asking how could their mound "plug up" that fast?
In a review of the county records, two things stuck out to me. First, the orifices in the mound were 1/8 inch, which is the smallest-size orifice you can use in Wisconsin (in our pressure component manual). A wise onsite teacher once taught me to always use 1/4-inch orifices (the largest size orifice allowed) and systems I install would always stand a better chance of not plugging up. I have kept to that recommendation and have had very good longevity with systems installed under that guidance.
I know what some of you are saying: Well, we use drip systems and those holes are much smaller yet. I’m discussing a typical pressure system such as a mound system or in-ground pressure system that does not have high pretreatment before the distribution piping. In pressure systems, design using the largest orifice you can. Since that teacher told me to use all 1/4-inch orifices, I realized most mounds I see plug up have smaller orifices; the recommendation was spot on.
The other thing I noticed in that plugged mound system is the installer used a program to design the system for him, or had someone design for him. When installers or designers are entering data into a program to do the design for them, they are at the mercy of the output of the system.
The following is not a blanket derision of all design software, but rather what I see as limitations that adversely affect system longevity and installation efficiency when systems are designed using basic Excel-based designs, as are typically performed in my area. This is me being old-school, but here’s why I have a problem every time I see the Excel-generated designs (from an installer perspective).
The same design that generated 1/8-inch orifices also has orifice spacings of 2.53 feet, lateral spacing of 2.67 feet and lateral lengths of 36.69 feet.
When I see numbers like these, I always think to myself, that design was "performed" by a person who has never installed a system, and I see this all the time. Why do I say the designer "performed" the design? They didn’t design anything. They entered some numbers into a program and obviously did not have the knowledge or care to make sure the numbers were rounded off. When I design pressure (or any) systems, I design with the installer in mind — nice round numbers.
My company installs a lot of systems, and if my designs were to slow down the crew by using numbers that were needlessly tedious for them, that lost time adds up. You may say, what’s the big deal, I can measure 36.69 for my lateral length. Sure you can, and so can I; but not as fast as you could measure 36.5 feet of length, or 30-inch orifice spacing, or 30-inch lateral spacing. Time is money.
Does your tape measure have tenths? Mine doesn’t. Lateral lengths, 36.69 feet; really? That is a lack of effort in the design by someone who doesn’t know the difference.
What I call actual designing is understanding where these numbers come from, and it’s easy to make every number (or at least almost every number) round off and result in human numbers. But to expect an installer to measure the ridiculous odd decimals is a lack of effort at the design stage.
I am always surprised to learn how many installers do not do their own designing. I understand in some regions, areas and states you don’t have that option. But where you do have the option, I would highly recommend learning to design your systems. Even if you won’t always design them yourself, it helps to understand where the numbers are coming from. Work closely with your designer to not only design the system appropriately but with the installation in mind.
I also always try to provide a larger soil absorption area than required by minimum and larger tank sizes when appropriate. In many instances these are offered as alternatives in my proposals so that the customer can weigh the option of more system for more dollars. But there are those systems where it just makes sense to bid the extra capacity right in my base bid. You know the systems. Twelve people in the house? Yeah, I’m going a little larger.
Use round numbers, use larger orifices when you can, and work closely with your designer to obtain better designs for both the longevity and installer perspectives.
About the author
Todd Stair is vice president of Herr Construction, Inc., with 34 years’ experience designing, installing, repairing, replacing and evaluating septic and mound systems in southeast Wisconsin. He is the author of The Book on Septics and Mounds and a former president of the Wisconsin Onsite Water Recycling Association.
