The entire public record of water hardness in Onawa is one number, taken at one well, on one day in December 2018. It read 480 milligrams per litre as calcium carbonate — 28.1 grains per gallon. That is the whole file.
| Onawa at a glance | What the record shows |
|---|---|
| Who supplies the water | Onawa Municipal Water Plant, PWSID IA6739095, serving 2,906 people in EPA SDWIS against a 2024 Census city estimate of 2,795 |
| Where it comes from | Missouri River alluvial wells between 110 and 137 feet, per the Iowa DNR Source Water Protection Tracker |
| Softened at the plant | No. No EPA SDWIS treatment record for IA6739095 carries a softening objective |
| Published hardness | 480 mg/L as calcium carbonate at Well #5, sampled 18 December 2018 — 28.1 grains per gallon, per the Iowa DNR sample database, analyte 84. No other hardness result exists for the city |
Twenty-eight grains is firmly hard water — roughly two and a half times the threshold at which the U.S. Geological Survey classes water as very hard, and enough to scale a water heater noticeably within a few years. And because Onawa runs no softening process, that figure is not reduced on its way to your house.
What it cannot tell you is whether Well #5 is representative of the wellfield, whether the aquifer has shifted since 2018, or what your own tap reads on a Tuesday in August. Compare that with Rock Rapids, which has published finished-water hardness five years running, and you can see how thin the Onawa record is by comparison.
We would rather say that plainly than dress up one seven-year-old well sample as a citywide fact.
Onawa's wells sit noticeably deeper than most Missouri River alluvial systems. The Iowa DNR lists Well #5 at 113.5 feet and Well #6 at 112 feet, both drilled in 1964 and both still active, with Well #7 at 115 feet from October 1979 on standby. A cluster of older wells — #1, #2 and #3 at 110 feet, plus two 1940s wells at 122 and 137 feet — are out of use.
Depth matters for a shallow-aquifer town: more overburden generally means slower response to surface conditions, but also a longer contact time with the sediments that put the calcium and magnesium into the water in the first place.
Sodium at the Onawa plant's entry-point tap measured 28, 30, 25 and 24 mg/L across the sampling record, against 23 mg/L in the raw water at Well #5. Almost nothing is being added.
That is a useful confirmation of the treatment picture: Onawa is not running an ion-exchange plant, which would push sodium up sharply, and it is not lime softening either. The water is being disinfected and filtered, and the mineral content is arriving largely as the aquifer delivered it.
Onawa's fourteen federal treatment records differ from its neighbours' in three small, specific ways, and together they sketch a distinct plant.
First, disinfection is by liquid sodium hypochlorite rather than the chlorine gas most towns in this region use — a different chemical delivered and stored differently, though the result in the water is comparable. Second, the filtration record specifies rapid sand filtration, alongside general sand filtration, aeration and potassium permanganate for iron and manganese. Third, corrosion control is by polyphosphate inhibitor.
Polyphosphate, like the orthopolyphosphate blend used at Rock Valley, works by sequestration: it keeps dissolved metals in solution so they do not stain or settle in the mains. It protects the distribution system. It does not take minerals out of the water, and it does nothing about hardness.
The same 18 December 2018 sample that gave Onawa its only hardness figure also measured total dissolved solids at Well #5: 540 milligrams per litre. That is the second number worth carrying around, because it is the one a softener will not touch.
Hardness is calcium and magnesium. Dissolved solids are everything — the sulphates, chlorides, bicarbonates and sodium that come with alluvial groundwater. An ion-exchange softener swaps the calcium and magnesium for sodium and leaves the total roughly where it started. Reverse osmosis is the stage that reduces it, and at 540 mg/L it earns its place at the kitchen sink.
The federal facility inventory sketches the rest of the system: thirteen facilities in all, of which three are wells and one is a treatment plant, feeding four storage structures — an active 0.3 million gallon elevated tank, two ground storage tanks at 0.25 and 0.225 million gallons, and one demolished elevated tank still carried on the record as inactive. That is a compact, conventional small-town system, and there is nothing in it that removes minerals.
Twenty-eight grains, unsoftened, on a supply with almost no published data. This is a town where we test before we say anything about sizing. Every price is all-in: equipment, installation, taxes and a lifetime parts warranty.
Annual maintenance is $199 a year for a tank-RO home and $249 for a tankless-RO home. A full diagnostic service call is $199; a known-issue trip is $99 plus the part. We offer 0% financing, and $100 off for military and first responders. Ask for the written breakdown before you schedule, or start one through our instant quote.
Monona County is thinly settled and a good share of its households are on private wells drawing the same Missouri River alluvium, with no plant and no monitoring in between. Iron, manganese and bacteria are the usual findings alongside the hardness. Our well water setup is a dual-tank system at $3,450, or $3,800 with tank RO, with UV disinfection at $700 and sediment pre-filtration at $500 when the readings call for them. We fit tank RO rather than tankless on a well, because high dissolved solids cost a tankless unit its pressure. Start with free well water testing.
We are licensed and insured, and our softeners are built from NSF/ANSI 44 certified components and our reverse osmosis systems are certified to NSF/ANSI 58. Installation is handled by licensed local plumbing professionals we vet, schedule and stand behind. Pricing is published and all-in, so the figure you read here is the figure on the paperwork. Distance and site conditions are the only things that can change it, and we tell you before you agree.
One well, one day, seven years ago is not enough to size equipment for your house — and it is more than most companies selling in Onawa will tell you they are working from. We come to you, measure hardness, iron and dissolved solids at your own kitchen sink, and leave you the readings and a written quote at no charge, whichever way you decide. Book your free in-home water test.
Sioux City · Missouri Valley · Council Bluffs · Le Mars · Carroll
The only hardness figure on public record is 480 mg/L as calcium carbonate at Well #5, sampled on 18 December 2018 — 28.1 grains per gallon, per the Iowa DNR sample database, analyte 84. No other hardness result exists for Onawa, so that single seven-year-old well sample is the entire published record.
No. No EPA SDWIS treatment record for PWSID IA6739095 carries a softening objective. The sodium figures confirm it: sodium at the plant entry-point tap measured 24 to 30 mg/L against 23 mg/L in the raw water, so essentially nothing is being added, which rules out an ion-exchange softening plant.
As a starting point, not as a specification. It is one sample from one well in December 2018, and it says nothing about how the rest of the wellfield reads, whether the aquifer has shifted since, or what your own tap delivers. That is why we measure at your kitchen sink before recommending or sizing anything.
Deeper than most Missouri River alluvial systems. The Iowa DNR Source Water Protection Tracker lists Well #5 at 113.5 feet and Well #6 at 112 feet, both drilled in 1964 and both active, with Well #7 at 115 feet from October 1979 on standby. Several older wells at 110 to 137 feet are out of use.
A Kind Water Co softener is $2,500, or $2,850 paired with reverse osmosis. The XL softener is $2,800, or $3,150 with RO, and a standalone RO system is $800 tank or $900 tankless. Every figure is all-in with equipment, professional installation, taxes and a lifetime parts warranty, with 0% financing and $100 off for military and first responders.
Every number on this page comes from a public record. Here is where to open each one yourself.
Whole-home water softening, filtration, and reverse-osmosis drinking water — professionally installed and built to last a lifetime.
Serving Marion, Cedar Rapids & surrounding Linn County communities
Kind Water Co is a d/b/a of Zero Cap Investments LLC · 2258 Bison St, Apt B, Marion, IA 52302
.webp)
