When a home inspector turned on the water and it ran down the drain, he concluded the onsite system must function. Then the home sale went one step further and had the tanks exposed so someone could watch the water in the tank while running water in the house. In this example, the water rose above the outlet pipe. The conclusion was that the soil absorption bed must be saturated or failed and no longer taking water.
I would say this conclusion is not yet correct, as an important step has been skipped: pumping the tank.
I’ve seen many times where a high level in a tank was mistakenly determined to be an issue with the soil absorption component of the system, when in reality the outlet pipe was compromised in some way.
By pumping a gravity system when it has a high level there is a great way to evaluate whether the cause of the high level is related to the soil absorption area or the pipe itself. I typically say that if you get steady and substantial drainback, the soil component is at an advanced stage of a saturated condition. The soil pores are plugged with a biomat and waterborne solids, and water is following the path of least resistance — back into the tank. Many times a customer will think it must then be a pipe problem, to which I’ll reply that the pipe is wide open or it would not be moving this much water back into the tank.
If you have a high level, then pump and get little to no drainback the outlet pipe might be compromised. My company has replaced dozens of outlet pipes of septic tanks and the system functioned normally; notably if the outlet pipe is cast iron, as cast iron pipes can often fail from the inside by accumulating debris.
In the example given at the beginning of this article, one person thought the system was fine; the other assumed the bed or distribution cell itself could be "failed." But without pumping, the outlet pipe was never analyzed. I have seen way too many times where a high level was misconstrued as a failed system when it was merely a pipe problem.
But there are many other reasons to pump the tank during an evaluation. Without pumping you’ll never know the condition of the tank. I’ve seen tanks at a normal level and once we pumped there were a dozen holes on each wall spraying water back into the tank. I never would have suspected that many holes in a tank that was at normal level.
A person built a brand-new farm house with a brand-new onsite system, but then decided to sell without ever moving in. For the sale they asked us to do an evaluation of the system and balked when we said we require pumping for every evaluation. The argument was, the system is brand-new and it hasn’t even been used, so there’s no reason to pump the tank. We held our ground and said if you don’t want it pumped, hire someone else. They stayed with us. When we pumped it, we discovered that the entire bottom of the tank was completely shattered. It was quite obvious that good, clean bedding stone wasn’t used and during backfill a rock cracked the bottom. The tank had to be replaced.
We have evaluated tanks that appeared perfectly fine (i.e., displaying a normal level) and upon pumping have found large roots and root masses indicating that the tank is either not watertight, not structurally sound or both.
The one thing you can typically see before you pump a tank is microbial-induced concrete corrosion; but even then pumping does make it easier to see, although it typically occurs above the waterline.
I worked with a group of onsite professionals for five years developing a curriculum of how to teach and perform evaluations for onsite systems for home sales. The committee worked on this and then it was peer reviewed by very well-established industry leaders, professionals, academics and regulators. The second item that was unanimously agreed upon was that pumping a system is an absolute must, an essential component of any complete evaluation of a system.
There are many times when a system looked very good to me, everything fell into place and could have easily been approved, and then we pumped the tank and found that the tank was cracked, had holes, or was somehow not structurally sound or not watertight. Pumping is a very important part of any complete evaluation of any onsite system.
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.
