Chloramines in Denver Metro Tap Water: What Colorado Homeowners Need to Know

What Are Chloramines?

Chloramines are disinfectants formed by combining chlorine with ammonia. The resulting compound — monochloramine — is a stable disinfectant that water utilities use to keep water safe from microbial contamination through the entire distribution system, from the treatment plant to your tap.

Denver Water, Aurora Water, South Metro Water Supply Authority (serving Highlands Ranch and Lone Tree), and Parker Water all use chloramines as their primary residual disinfectant. The Town of Castle Rock does as well.

The switch from free chlorine to chloramines happened in the 1990s and 2000s across most of the metro area, driven by EPA regulations targeting disinfection byproducts — specifically trihalomethanes (THMs) and haloacetic acids (HAAs), which form when free chlorine reacts with organic matter in water. Chloramines produce fewer of these regulated byproducts.

Why It Matters for Home Filtration

Here's the problem most homeowners don't know: standard activated carbon filters are significantly less effective at removing chloramines than free chlorine.

Standard activated carbon (the type in most pitcher filters like Brita, basic under-sink filters, and refrigerator filters) removes free chlorine very well through a process called adsorption. Chloramines, however, require a different process — catalytic reduction — to be removed effectively. Catalytic carbon, specifically carbon that's been treated to enhance its catalytic properties (such as Jacobi CENTAUR, Donau Carbon ACM, or similar), breaks down chloramines efficiently.

This matters because most homeowners who buy a pitcher filter or a basic carbon block filter believe they're removing what's in their water. For chloramine-treated water, they're largely not — the filter provides minimal chloramine reduction, and the water coming through may still smell or taste like a swimming pool to people who are sensitive to it.

Chloramines and Disinfection Byproducts

The EPA switched utilities to chloramines partly to reduce trihalomethanes (THMs) and haloacetic acids (HAAs) — and it worked. But chloramines create their own set of byproducts, including nitrosamines (particularly NDMA — N-Nitrosodimethylamine), which have drawn increasing regulatory attention.

NDMA is classified as a probable human carcinogen. The EPA has a health advisory level of 10 nanograms per liter (0.01 ppb). Denver metro utilities generally meet this standard, but NDMA is one of the "unregulated" contaminants being evaluated for future regulation.

For homeowners concerned about this specifically: reverse osmosis is the most effective at-home treatment for NDMA, reducing it by 90%+.

Chloramines and Certain Household Uses

Beyond drinking water, chloramines matter in a few specific contexts:

Fish tanks and aquariums

This is well-known in the aquarium hobby: chloramines are toxic to fish and cannot be neutralized the same way free chlorine can. Standard dechlorination tablets (sodium thiosulfate) neutralize free chlorine but not chloramines. Aquarium owners in chloramine-treated water areas need to use a dechlorinator specifically formulated for chloramines (products containing sodium thiosulfate plus ammonia neutralizers, or specifically labeled for chloramine removal).

Home brewing

Chloramines negatively affect beer fermentation and flavor. They react with phenolic compounds to create chlorophenol — an off-flavor compound detectable at very low levels that can ruin a batch of beer. Home brewers in the Denver metro area who use tap water need to specifically remove chloramines, either with campden tablets (potassium metabisulfite, which works well at very low doses) or with a catalytic carbon filter.

Dialysis patients

This is a medical-grade concern handled by dialysis centers — but worth noting: chloramines are dangerous in dialysis water and require specific treatment. Home dialysis patients should work with their medical team on appropriate water treatment.

What to Do About Chloramines in Your Home

The practical solutions for most Front Range homeowners:

For whole-house treatment

A catalytic carbon whole-house filter installed at the point of entry removes chloramines before water reaches any fixture, appliance, or shower. This is the cleanest solution — your shower water, laundry water, and drinking water all benefit. Our whole-house filtration systems use catalytic carbon media specifically for this reason.

For drinking water specifically

A reverse osmosis system under the kitchen sink handles chloramines effectively and also removes TDS, nitrates, and other contaminants. If your only concern is drinking water quality (not whole-house), an RO system is the most thorough point-of-use option.

For shower water

Shower filters are a popular purchase, but most of the mass-market options (KDF-55 media) work better on free chlorine than chloramines. Look specifically for shower filters using catalytic carbon or KDF-85 (a different media formulation with better chloramine performance) if chloramine removal at the showerhead is your goal.

If you have questions about what's specifically in your water supply and the most effective way to address it for your home, we're happy to test and advise — no sales pressure, just real information from people who've been doing this in Colorado since 2009.