Des Moines Water Is Hard — Here's What It Costs You Each Year
7 GPG · 120 ppm · -4% vs US average · 2024 report
Source: Des Moines Water Works, 2024 report
HardDes Moines water is hard at 7 GPG (120 ppm). That is soft-to-moderate water; most homes here don't need a softener.
How we calculate this: based on the Battelle Memorial Institute study commissioned by the Water Quality Association (WQA), hard water is estimated to cost the average affected household roughly $800/year in 2010 dollars (~$1,230 today, after ~54% inflation). We scale that by 7 GPG versus a ~10 GPG reference. The percentages above come from the Battelle Memorial Institute study (commissioned by WQRF), the US Department of Energy, and the Water Quality Association. This is an estimate — not a certified per-household figure — and actual savings vary by water use, fuel type, and local rates.
Hardness
Parts per million
vs US average
Contaminants above EWG guideline
How Des Moines Compares
Water hardness scale
| Classification | Grains per gallon (GPG) | mg/L (ppm) | What it means |
|---|---|---|---|
| Soft | 0–3.5 | 0–60 | No scale; softener unnecessary. |
| Slightly Hard | 3.5–7 | 60–120 | Minor spotting; conditioning optional. |
| Hard← your water | 7–10.5 | 120–180 | Visible scale; softener recommended. |
| Very Hard | 10.5+ | 180+ | Heavy scale; whole-home softener strongly recommended. |
Why Is Des Moines Water So Hard?
Des Moines gets its tap water from two working rivers: the Raccoon River and the Des Moines River. That makes this a surface-water city, plain and simple. Des Moines Water Works pulls from those rivers, treats it, and sends it to your faucet. So the hardness you’re dealing with isn’t coming from some deep limestone aquifer under your feet. It’s coming from what those rivers pick up on their way to the city.
Here’s the whole story. The Raccoon River winds through some of the most intensely farmed land in the country, the rolling glacial plains of northwest and central Iowa. The Des Moines River follows a similar path down from southern Minnesota. Both rivers drain a watershed that sits on top of thick deposits of glacial till, which is a messy mix of clay, sand, gravel, and crushed-up rock left behind by glaciers that retreated roughly 12,000 years ago. That till is loaded with calcium and magnesium compounds, mostly from limestone and dolomite fragments that the glaciers scraped up and ground down as they moved through the region.
Rain and snowmelt soak into this soil and run off into the rivers, and water is a relentless solvent. As it moves through the ground and over the surface, it dissolves carbon dioxide from the soil to form a weak carbonic acid. That mild acid chews on the calcium carbonate in the limestone fragments, pulling calcium and bicarbonate into solution. The same thing happens with magnesium. By the time the Raccoon and Des Moines rivers reach the water treatment plant, they’re carrying a measurable load of dissolved hardness. That’s why Des Moines sits right at 7 GPG, which the USGS classifies as hard water. You’re not imagining it if your glasses spot or your soap doesn’t lather the way it should. The rivers are doing exactly what rivers over limestone-rich glacial till do.
One more layer worth knowing. Des Moines Water Works blends water from both rivers depending on the season and flow conditions. The Raccoon tends to carry more dissolved solids because its watershed is so heavily agricultural, while the Des Moines River can dilute things somewhat during higher flows. The result is that your hardness can swing a bit through the year, but it averages out to that 7 GPG mark. It’s not a static number stamped in stone. It’s a living measurement of two working rivers doing their geological job.
How Des Moines Compares to Nearby Cities
If you live in Des Moines proper, you’re drinking treated surface water from the Raccoon and Des Moines rivers. That puts you in a different category than some of your neighbors who rely on groundwater.
The surrounding metro communities largely draw from the Jordan Aquifer and other deeper sandstone formations. That’s a whole different water story. Groundwater in that part of Iowa has had centuries to sit in contact with sandstone and carbonate rock, which typically means it comes out harder than surface water. So if you’ve got friends in Ankeny, Johnston, or Urbandale who complain about scale buildup, they’re likely dealing with water that tests harder than yours. Their water has been marinating in mineral-rich rock for a long time, while yours took a relatively short trip down the river.
That said, don’t assume your 7 GPG is a walk in the park. It’s right at the USGS threshold where water is officially classified as hard, and it’s close to the national average of about 7.3 GPG. The EPA doesn’t regulate hardness as a health hazard, so this is purely an aesthetic and nuisance issue. But nuisance adds up. According to the WQA, hard water raises energy, appliance-wear, and cleaning costs, and that figure scales with your actual hardness level. You can run the numbers for Des Moines specifically with the calculator on this page.
The practical difference between you and your groundwater neighbors comes down to consistency. River water changes with the seasons, the weather, and what’s happening upstream. Groundwater stays more stable year-round. So while your hardness might hover around that 7 GPG mark on average, it can creep up during dry spells when the Raccoon runs low and the mineral concentration concentrates. That variability is just part of living on surface water in the Corn Belt. Fair enough.
How does Des Moines stack up against the rest of Iowa? It's hard at 7 GPG — Sioux City, Waterloo, and Iowa City sit nearby with different numbers. See the full hardest-water ranking for context.
See where Des Moines sits on the Iowa water hardness map →
Want the broader explainer on what hardness actually is and how it behaves? Read hard water vs. soft water, explained.
What 7 GPG Actually Does to a Des Moines Home
At 7 GPG, hard water stops being subtle in a Des Moines home. Here's what it actually does:
- Water heater efficiency drop. The US Department of Energy (and its equivalent studies) attribute scale as the single biggest efficiency killer in hard-water homes — at 7 GPG, your heater operates roughly 6% below where it would on soft water, which shows up directly on the energy bill.
- Fixture and glassware scale. White mineral deposits build on faucets, showerheads, and dishes within weeks of cleaning.
- More detergent. The Water Quality Association notes hard water can require 50–75% more soap to achieve the same cleaning — and fabrics wear faster from mineral abrasion in the wash cycle.
- Shortened appliance life. Dishwashers, washing machines, and water heaters accumulate internal scale that quietly cuts their service life.
The Battelle Memorial Institute's study — commissioned by the Water Quality Research Foundation — is the cleanest proof: water heaters on untreated hard water failed in under 2 years of the 10-year test, while identical units on softened water ran the full decade. The mineral damage is real and measurable.
Do You Need a Water Softener in Des Moines?
Yes, for most homes. At 7 GPG, Des Moines water is hard enough that a whole-house ion-exchange softener pays for itself — through longer appliance life, less detergent, and less descaling. The Battelle water-heater finding alone (untreated units failing in under 2 years) makes the case at this hardness.
At 7 GPG a salt-free conditioner will reduce scale but won't remove the minerals — you'll still get the soap and skin effects. For actual softening, ion exchange (a traditional softener) is what removes hardness.
What Size Softener Does Des Moines Need?
Sizing a softener is a two-number equation: your household's daily water use × your hardness. The rule of thumb is grains per day = (people) × (75 gallons) × (GPG).
- At 7 GPG, a family of four uses roughly 2,100 grains of hardness per day.
- A 32,000–48,000-grain softener regenerates roughly every 12–18 days — within the 3–7 day window that keeps salt and water use efficient.
- Round up, not down: an undersized unit regenerates too often and wastes salt. Metered (on-demand) regeneration saves the most salt and water.
For Des Moines at 7 GPG, a 32,000–48,000-grain metered softener is the safe default for a 3–4 person home. A larger household, or one with unusually high water use, should size up to 64,000 grains.
What Are the Signs of Hard Water in a Des Moines Home?
At 7 GPG (120 ppm), Des Moines residents notice significant hard-water effects. The USGS classifies water above 7 GPG as hard and notes it causes measurable physical damage to plumbing and appliances.
- White or grey crust on faucet aerators, showerheads, and around drains — calcium carbonate depositing as water evaporates.
- Spotty glassware even after a full dishwasher cycle — mineral film left behind when water dries.
- Falling water-heater efficiency — scale insulates the heating element, forcing the unit to work harder and pushing up the energy bill.
- Flat, stiff hair — calcium bonds to hair proteins and prevents shampoo from rinsing clean.
- Dry, itchy skin — dissolved minerals disrupt the skin's moisture barrier.
- Weak soap lather — hardness ions react with soap to form insoluble scum instead of suds.
- Shorter appliance life — washing machines, dishwashers, and coffee makers accumulate internal scale.
The Battelle Memorial Institute study commissioned by the Water Quality Research Foundation found untreated very-hard-water heaters failed in under 2 years, versus a full 10 years on softened water. At Des Moines's 7 GPG, that equipment degradation compounds faster than most homeowners expect.
What's in Des Moines's water
Detected contaminants reported for Des Moines Water Works (EPA system ID IA7727031).
Source: EWG tap water database (Aug 2026).
Every detected contaminant is below the legal limit. Some are still above EWG's stricter voluntary health benchmarks — common nationwide, shown below.
| Contaminant | Typical level | EPA legal limit | EWG guideline | Status |
|---|---|---|---|---|
| Bromodichloromethane | 15.8 ppb | unregulated | 0.06 ppb | Above EWG |
| Bromoform | 3.09 ppb | unregulated | 0.5 ppb | Above EWG |
| Chloroform | 25.1 ppb | unregulated | 0.4 ppb | Above EWG |
| Chromium (hexavalent) | 0.712 ppb | unregulated | 0.02 ppb | Above EWG |
| Dibromoacetic acid | 2.81 ppb | unregulated | 0.03 ppb | Above EWG |
| Dibromochloromethane | 10.9 ppb | unregulated | 0.1 ppb | Above EWG |
| Dichloroacetic acid | 6.59 ppb | unregulated | 0.2 ppb | Above EWG |
| Haloacetic acids (HAA5) | 10.1 ppb | 60 ppb | 0.1 ppb | Below limit |
| Haloacetic acids (HAA9) | 12.7 ppb | unregulated | 0.06 ppb | Above EWG |
| Nitrate | 1.72 ppm | 10 ppm | 0.14 ppm | Below limit |
| Total trihalomethanes (TTHMs) | 55.4 ppb | 80 ppb | 0.15 ppb | Below limit |
| Trichloroacetic acid | 0.76 ppb | unregulated | 0.1 ppb | Above EWG |
Levels are system-wide utility averages. The legal limit is the EPA's Maximum Contaminant Level (MCL). EWG also flags 12 contaminant(s) as exceeding its own stricter (non-legal) health guideline — shown as an informational note only, not a safety claim.
Not sure what these levels mean for your health? Read our complete contaminants guide — what's detected vs. what matters, and how to read the numbers.
Best Treatment for Des Moines Homes
At 7 GPG you want actual removal, not just scale prevention. Two pieces of equipment cover most needs:
Fleck 5600SXT Whole-House Softener
The industry-standard residential softener. Metered regeneration saves salt and water; 48,000-grain capacity handles Des Moines's 7 GPG for a family of four. Digital control head, 10-year tank warranty. This is what most local plumbers install.
check current price
Check price on Amazon →APEC ROES-50 Reverse Osmosis (drinking water)
The softener handles hardness; the under-sink RO handles everything you drink. Removes disinfection byproducts, chromium-6, and other contaminants a softener leaves untouched.
check current price
Check price on Amazon →
A whole-house water softener pays for itself in roughly 14 months at Des Moines's hardness level — after that, the savings accrue every year.
If contaminants concern you — add a drinking-water filter
The softener handles hardness; a drinking-water filter removes Chromium-6 and removes Nitrate — if Des Moines's reported levels concern you. EPA / NTP: Chromium-6 (hexavalent chromium) is a known carcinogen when inhaled and is linked to stomach and intestinal tumors in drinking-water studies. EPA: Nitrate (above 10 mg/L as nitrogen) can cause "blue baby syndrome" (methemoglobinemia) in infants and is associated with certain cancers at sustained exposure. For a full breakdown of what each filter type removes, see best whole-house water filters.
How Do You Test Water Hardness in Des Moines?
This page reports Des Moines's system-wide average (7 GPG), but your tap can vary slightly by neighborhood, pipe age, and in-home filtration. For a step-by-step, see how to test your water hardness at home — it walks through test strips, the free soap-shake check, TDS meters, titration kits, and certified lab tests.
- Test strips (~$10) give a GPG reading in about 30 seconds and are accurate enough to decide whether to invest in treatment.
- TDS meter (~$15) measures total dissolved solids, a rough hardness proxy — but it doesn't separate hardness from other minerals.
- Lab test — most water treatment companies in Des Moines offer free in-home tests (expect a sales pitch); for an independent result, the EPA maintains a list of certified labs.
Note: the EPA doesn't regulate hardness (it's a nuisance, not a health hazard), but the EWG Tap Water Database tracks contaminants above health guidelines for Des Moines's utility — see the table below.
Compare Des Moines to Other Iowa Cities
Other Hard Water Cities
Explore More
Frequently asked questions
Is Des Moines water hard or soft?
Des Moines, Iowa water is hard at 7 grains per gallon (120 ppm). That is generally considered soft to moderately hard.
How much does hard water cost the average Des Moines household?
Based on the WQA-commissioned Battelle Memorial Institute study, hard water is estimated to cost the average affected household roughly $800/year in 2010 dollars (~$1,230 today after ~54% inflation) — an estimate, not a measured per-household figure. Scaled to Des Moines's 7 GPG hardness, that works out to about $861/year (or ~$71.75/month) for a typical home — see the calculator on this page for the full breakdown.
Does Des Moines need a water softener?
Probably not — at 7 GPG your water is mild enough that a test kit is a better first step than a full softener.
Why is Des Moines's water hard?
Hardness comes from the geology of Des Moines's water source. Raccoon River + Des Moines River dissolves calcium and magnesium as water moves through the ground, and those dissolved minerals are what "hard water" means.
How do I test my water hardness in Des Moines?
Use a home test kit (test strips for a quick read, or a TDS meter for dissolved solids), or check your utility's annual Consumer Confidence Report (CCR). For lab-accurate results, send a sample to a certified lab.
Who supplies Des Moines's water?
Des Moines water is supplied by Des Moines Water Works. Its annual water quality report (Consumer Confidence Report) is the authoritative source for local hardness and contaminant levels.
What's the difference between grains per gallon and ppm?
1 GPG (grains per gallon) equals 17.1 ppm (mg/L). To convert: 7 GPG × 17.1 = ~120 ppm. Water is "hard" above roughly 7 GPG (120 ppm).
Sources & data
Hardness and water-quality data compiled from authoritative public sources.
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