I received a call from someone who said he was having issues with his mound system. In trying to assess the situation over the phone he said it pumps fine, no alarm, but he wants us to look at the mound itself.
The usual suspects are what we consider: A flush-out valve broken by a lawn mower, an observation pipe broken by a lawn mower, surfacing of effluent due to a mature biomat, wildlife digging holes in it.
Upon arrival at his site, none of these were his concern and it was obvious he has kept his system as well maintained as I’ve seen for an 18-year-old system.
In the center of the lowest part of the downslope toe of the mound were two bulges that appeared to be coming from the mound — two small mounds where two small mounds shouldn’t be.
Due to following the contour as a mound should, the mound was concave. The entire lot, and the neighbors' lot, drained surface water to the upslope side of this mound and because the mound was concave, that’s where the water pooled — right in the center of the upslope side of the mound. With that much water pressure pushing from the upslope side of the mound, it is quite possible (and probable) that the small mounds directly opposite were sand pushing from the bottom of the mound out the low side of the mound.
I do realize this might be basic for some, but just because the mound is drawn at a concave shape like a banana due to contour lines, does not mean you can’t fill the upslope side to direct the surface water around the mound. It is imperative that water be directed around the mound (to one end or both). One of the easiest ways is to fill the upslope side to direct water to each end, so that can be achieved. Stormwater should not be allowed to pond on the upslope side of a mound.
The owner with the 18-year-old mound asked how he can maximize its longevity, and I told him first and foremost of the urgency to fill in the upslope side to divert water away.
Here are some other tips I gave him to maximize the longevity of the mound:
- We checked each of the three access covers. Because the lot was sloped I wanted to make sure the covers weren’t flush at grade and susceptible to surface water inflow. His access covers had risers, keeping each cover at least 4 to 6 inches above grade, which is very good and highly recommended.
- I told him to annually do the dye test/food color test of each of his toilets: put a tracing dye or food color in the tank of each toilet and, without flushing, see if the color shows up in the bowl of the toilet — and if it does, to have the toilet repaired to stop the silent, unwanted flow of water through the toilet(s). Silently leaking toilets can add a lot of water in the system and can singlehandedly cause hydraulic overload of a system. I had one large commercial establishment where a very large holding tank was constantly filling up very fast. When we tested the toilets a few of them were silently leaking and repairing the toilets stopped the tanks from filling up so fast.
- The customer with the mound system said his water softener and iron filter recharge ran into the system. I did discuss the importance of having those two items flow anywhere but into his system. I told him that it was important he have these two rerouted out of the system. In our state (Wisconsin), code (thankfully!) allows water conditioning devices’ recharge to not have to go into an onsite system. Recently I saw firsthand the devastation that an iron filter recharge will do to a system. When I saw how bad it was, I reached out to the best water conditioning person I know and he totally agreed that iron filter recharge is indeed detrimental to onsite systems and should be routed anywhere but into the onsite system.
I was involved in a replacement system that immediately had a very thick brown mat on top of the water in all three tanks (including the pump tank after an effluent filter!). The tanks were pumped clean, and within two weeks, the tanks were full and the thick, mud-like mat was back on top of the water, just as thick in all three tanks again. Through a process of elimination, we had the customer unplug the iron filter after talking with the water conditioning person. Once the iron filter was unplugged, the brown mat never came back. Just the thick iron buildup on the sink in the basement where the iron filter recharged to should have alerted someone.
Second, and anecdotally only, I’ve seen a system that had failed, and when the installer attempted to recore/rebuild the mound, this second house with iron filter issues had soil beneath the mound that not only did not match the soil test, it was not able to be reused to rebuild the mound. Was this soil augmentation from the iron filter also? This was only their guess, but from what I have seen nobody should have their iron filter recharge go into an onsite system.
I was lucky with this customer — he was trying to be thoughtful and proactive regarding his system. Those customers seem rare, but it is encouraging to see someone ask how they can best take care of their system.
Keep up the good work out there and stay safe.
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.
