Filtering a heavily clay-laden Tennessee well

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Rick Ross

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I recently bought a 3-bedroom, 2 1/2-bath house from my neighbors at the top of a big hill in the country just north of Nashville, TN. I am the 3rd owner of the house, which was built in 2007. An 80-foot well was completed in October, 2007. The well has 6-inch galvanized casing all the way down, presumably slotted to allow water in. I spoke to the driller's son, and he said that the bottom is in bedrock. At the time the driller filed his report with the State of TN he reported the well to be yielding 30 gpm of good clear water, with static water level at 40 feet. The driller's report formation log says "OVERBURDEN(GRAVEL)" and the comments say "SHALE TRAP @ 38 FT GRAVEL ON TOP OF TRAP THEN BENTONITE." The report also states there is crushed limestone backfill material from 3 feet to 25 feet. The galvanized casing comes up a little over 1 foot from the ground level at the top.

We don't know what type of pump the original owner used or at what depth the pump sat. The 2nd owner (my former neighbor) installed a 3/4 hp 10 gpm Franklin pump at 60 feet in 2020. The well has 1-inch 160 psi Silver-Line poly pipe up to a pitless adapter where the water goes into the house's garage. The water goes first into a Well Mate pressure tank and then to a 10 gpm 2-stage Pura UV20-2-SD5 whole house filter. The UV20 has a 2.5x20 5-micron poly filter as a first stage and a UV second stage. The water then proceeds into the house distribution system with no further filtration.

When we arrived the water in the house was horrendous with red clay sediment everywhere. Several of the faucets wouldn't even flow, and those that did ran with heavily clay-laden water that ranged from very rosy translucent (at best) to deep red-brown opaque. The toilet tanks were completely coated with about 1/4-inch of sediment, and my wife and I were wondering what we had gotten ourselves into.

I removed the 5-micron filter from the Pura UV20 and found at least 5-6 inches of clay in the sump with the filter completely occluded. The UV stage of the Pura was utterly compromised with thick, opaque clay completely obscuring the quartz enclosure for the UV light. I cleaned both sides as best I could and installed a new 5-micron poly filter before taking a look at the Well Mate pressure tank. When I drained the pressure tank an amazing amount of clay sediment came out. I can't be certain, but I'd estimate that at least 8 inches of sediment was in the bottom of the tank, maybe more. I disconnected the tank supply side to see what was coming up from the well pump, and it was flowing very slowly with heavily clay-laden sediment in the water.

At this point I sounded the well and discovered that nearly 20 feet of sediment had accumulated, raising the bottom from the original 80-foot level up to the 60-foot level where the pump sits. I decided to pull the pump up to inspect it. The pump bottom was suctioned hard into the sediment and required a great deal of force to get it loose to raise it. I rented a 185 cfm diesel compressor and was able to blow the crud loose and clear the well back down to its original bottom at 80 feet. I ran the pump for the better part of 2 days and finally got somewhat clear water coming consistently. I observed that I could pump about 800-1000 gallons at full speed without dropping the static water level, but after that the well yield dropped considerably to about 3 gpm, which I discovered was coming in from somewhere around 45 feet down. I could actually hear it pouring out and splashing when the water got drawn down below that level.

After consulting a local well guy who is familiar with the well, I dragged a 325-gallon water tote up the hill. I filled it and released it quickly back into the well in hopes of creating some backpressure that might clear some of the sediment he suspected had built up on the outside of the casing slots. I repeated this 5-6 times, but I'm not certain if it had much beneficial effect. I don't want to go forward with full-blown hydrofracking at this point, as I don't expect to use more daily water than the well can currently yield at the pump's full speed. This cleaning process has placed extraordinary demands on the well, but I don't think it'll be so heavily worked in normal daily use.

So, now I have the sediment cleared from the bottom and am pumping somewhat clear water from the 60-foot level, although there is still a small amount of sediment and a slight odor to the water. I don't know how quickly the sediment will re-accumulate at the bottom? Additionally, we have been in a bit of a drought here for several weeks, so I don't know how much sediment I'll see after the rainy season begins again later in the Fall? What I do know for sure is that a heck of a lot of red clay has been pumped up from that well over the past 16 years, and I have no reason to believe it won't continue. Instead, it seems conservative to expect that the clay will continue to come up, so I need to adapt the system to manage and filter it.

Here's the rub. The Well Mate pressure tank is capturing a huge amount of clay sediment. I have flushed it about 2-dozen times but can still see nasty, deep-red crud coming out as it starts filling. It is basically functioning as a storage tank for the crud, and I can't seem to get it completely cleaned out. I'm thinking I'll probably remove it and install a PK1A Pside-kick CSV instead, but I'm worried about that getting jammed up with clay, too. What I really want to do is install an automatic backwashing Turbidex filter ahead of the PK1A and pressure switch, and then I'd install some kind of low-pressure sensor to shut the pump off if the filter gets too clogged up. This would hopefully prevent the bulk of the sediment from reaching the CSV and subsequent filters.

After the CSV I am thinking of installing a series of 2-3 additional Big Blue type filters to get down to the 1-micron level. If there are sub-micron cartridges available, I'd probably want to use those, too. The Turbidex filter should get me down to the 5-micron level, so I would hope the Big Blue poly filter cartridges wouldn't get jammed up and require replacement too quickly.

If you have read this far, then I am deeply grateful and really appreciate you. I know the wealth of knowledge and expertise in this community is unparalleled, and I hope some of you will have insights and ideas to share before I rush out and start buying and installing new equipment. This well is going to need a much more robust solution than the first two owners had in place. I'm hoping your insights will help me get that solution designed and implemented. Thank you!
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