Chloramine towns vs chlorine towns: why the difference changes the filter you need

Almost every homeowner who calls us asks about hardness first. That's fair, because hardness is what you can see on the shower glass. But there's a second question on every city water record we keep, and it's the one that actually decides what kind of filter goes on the wall: what is your utility using to disinfect the water? Around here the answer is either free chlorine or chloramine, and those two are not the same problem. Austin and I size a lot of jobs off this one line item, so here is what our own data says, town by town.

How this was built: This pulls every town in Jones Air & Water's own 57-town water dataset, built from utility consumer confidence reports, DNR and EPA well data, and our own in-home testing, pulled in 2026. There is no tidy "disinfectant" column in that file. The disinfectant is named inside each town's written record, so I went through all 57 records and sorted them by what the record actually says. Where a record doesn't name a disinfectant, I've left that town out rather than guess.

The count: chloramine is the minority here, but it's concentrated

Out of our 57 town records, 8 name chloramine outright. 31 name chlorine or chlorine disinfection byproducts and not chloramine. 1 town, Cottleville, names both, because it depends on which utility serves your street. The remaining 17 records don't name a disinfectant at all, mostly the ones where our notes are focused on private wells, and I'm not going to invent an answer for those.

So chloramine is roughly one town in seven of the ones we have an answer for. But it isn't scattered randomly. Three of the eight are right together in Madison County, Illinois, and three more are clustered in Jefferson County, Missouri.

The eight chloramine towns we serve

Our records give the chloramine dose for four of them: Alton at 2.5 to 3.1 ppm, Godfrey at 2.9 ppm average across a 2.5 to 3.1 range, Grafton at 2.9 ppm, and Granite City the highest at roughly 3.1 to 3.5 ppm.

The thing I assumed, and what the data actually says

I went into this expecting the chloramine towns to carry the worst disinfection byproduct numbers. That's the common wisdom in this trade. When I lined all 57 records up, it isn't true, and I'd rather print that than the version I expected.

The eight chloramine towns do sit in a consistent band, 47 to 56 ppb of total trihalomethanes, every one of them. But the towns running plain chlorine cover a far wider spread, and the top of that spread is worse than anything on the chloramine list. Jerseyville reports TTHMs at 77 ppb, which our record notes is 96% of the federal limit. Festus is at 71.7 ppb. Herculaneum is at 71.6 ppb with HAA5 up to 94.5 and one tap above the federal limit. Crystal City runs a 66 ppb average with a single sample at 88.5 ppb, over the 80 ppb EPA limit outright. Then Wood River at 56 and High Ridge at 53. Down at the other end, Villa Ridge is at 0.72 ppb.

So the four highest TTHM figures in our entire dataset belong to towns whose records never mention chloramine at all. Byproducts track the source water and the pipe network, not the letter on the disinfectant. If somebody tells you chloramine automatically means more junk in your water, our own numbers don't back that up.

What chloramine actually changes is narrower and more practical: how hard the disinfectant itself is to get out of the water at your sink. That's a filter question, and it's the whole reason this distinction is worth knowing.

The other thing that surprised me: chloramine towns are not the hard ones

Average those eight chloramine towns straight across and you get about 10.8 grains per gallon. Five of the eight grade C. That's middle of the road for our territory. Meanwhile the hardest towns in our whole dataset, Wood River at 24.5 and Edwardsville at 24.0, both run free chlorine, at 1.4 ppm and about 1.2 ppm respectively.

That's the part people get backwards. Hardness and disinfectant are two separate lines on every town record we keep, and they are two separate problems with two separate fixes. Wood River is a brutal softener job and a simple filter job. Arnold at 8.0 grains is a modest softener job and a more demanding filter job. Neither one is "worse water" overall. They're different water.

Why chloramine is harder to filter, in our own notes

This isn't my opinion, it's what's written on the town records themselves. Our Alton entry says the chloramine is "hard to remove, won't gas off." Our Grafton entry says it "resists standard carbon filters," and the Grafton readout adds that because the town is chloraminated rather than chlorinated, "the cheap fridge and pitcher filters barely touch it." Arnold, Barnhart, Imperial and Weldon Spring all carry the same short note: harder to filter than chlorine. The Imperial record spells out why in four words, chlorine plus ammonia. That ammonia is the whole difference.

Free chlorine is comparatively easy. It will gas off on its own if you leave a pitcher on the counter, and a modest carbon filter handles it. Chloramine won't do either of those things. It's built to stay in the water all the way to the far end of the pipe network, which is exactly why utilities like it and exactly why it's a nuisance at your tap. Our Godfrey record notes the other side effect we see on service calls: it "eats rubber gaskets and fixtures."

Two towns that prove you have to check, not assume

Cottleville is the one I warn people about. Its record lists the disinfectant as "Chlorine (PWSD #2) / Chloramine (MO American)." Same town, two utilities, two different answers. Your neighbor's filter recommendation may be flatly wrong for your house depending on whose line runs down your street.

Granite City is the other one. Its record notes chloramine at roughly 3.1 to 3.5 ppm, and then adds that the system "switches to free chlorine each Aug-Sept." Our readout for that town says the chemical taste and smell "spikes hard every Aug-Sept when the utility flushes the mains with straight chlorine." If you live in Granite City and your water tastes fine in April and awful in September, you're not imagining it and your filter isn't broken. That's the annual chlorine burnout, and it's in the record.

What I actually recommend, by camp

If you're in a free chlorine town, taste and odor is usually the main complaint, and a carbon filter sized for your house takes care of it without much drama. Your bigger spend is generally the softener, because the free chlorine towns include the hardest water we treat, Wood River and Edwardsville among them. The exception is the handful of chlorine towns carrying real byproduct loads, Jerseyville, Festus, Herculaneum and Crystal City in particular. If you're in one of those, I'd treat carbon as seriously as I would in any chloramine town, and I'd want to talk about drinking water separately.

If you're in one of the eight chloramine towns, don't buy a pitcher filter and expect it to fix the taste. You want real carbon contact time on the whole house. The backwashing carbon filter we install is rated to remove up to 97% of chlorine and chloramines with a regenerating carbon bed, and our own product notes point out it protects plumbing, appliances and the softener itself. If drinking water taste is the specific complaint, that's where reverse osmosis at the kitchen sink earns its keep.

Either way, the softener is a separate decision from the filter. Size the softener to your grains, size the filter to your disinfectant. If you want your grains number first, the hardest water towns we serve, ranked by the numbers has the whole list, and what hard water actually costs you every year puts a dollar figure on the hardness half of the problem. For the county level view of one of these areas, see St. Charles County town by town.

One honest limit on this post

Seventeen of our 57 records don't name a disinfectant. If your town isn't in either camp above, that's not a verdict on your water, it just means our file doesn't answer that particular question for you yet, usually because our notes for your area are focused on private wells. And if you're on a private well, none of this applies to you at all. Nobody is dosing your water with anything. You have a different list to worry about, which I went through in well water vs. city water: what 30 years of testing taught me.

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