How Hard Is Poway's Water? Hardness, Chloramine, and What Homeowners Should Know

How hard is Poway's water?

Poway's CY2025 report lists hardness of 218 mg/L for its imported water, with a range of 214 to 223 mg/L, and 237 mg/L for Lake Poway water. Divided by 17.1, 218 mg/L is about 12.7 grains per gallon. The U.S. Geological Survey classes water above 180 mg/L as very hard.

One detail worth knowing: Poway's reports give hardness for the water coming in, the imported supply and Lake Poway, rather than for water in the pipes after treatment. Treatment does not remove hardness, so the source number is a reasonable guide to your tap, but the only way to know your exact number on a given day is to test at the tap.

Why does Poway's water hardness change so much from year to year?

Because the imported water is a blend of Colorado River water and State Water Project water from Northern California, and the blend changes. Colorado River water carries more dissolved minerals. Poway's imported water averaged as low as 117 mg/L in 2017 and as high as 284 mg/L in other years of the past decade.

That is a wide swing for one city. In a year heavy on State Water Project water, Poway's imported supply can come in moderately hard. In a year heavy on Colorado River water, it can test well into very hard. Even within 2023, the imported water ranged from 165 to 291 mg/L.

Total dissolved solids track the same way, from 283 mg/L in 2017 to 624 mg/L in the reports that printed the highest value. The practical point: a hardness number you found online for Poway may be from a very different year than this one, and a single test at your tap tells you where things stand now.

Does Poway use chlorine or chloramine?

Poway has used chloramine. Its reports from CY2016 through CY2024 describe two methods of disinfection, chlorine and then chloramines, a combination of chlorine and ammonia, and list the residual as chlorine residual as chloramine. The CY2025 report changed that wording and lists the residual simply as chlorine, without explaining the change.

A change in how a report is worded is not the same as a change in treatment, so we are not going to guess. If it matters to you, and it does if you keep fish, use home dialysis, or are choosing a carbon filter, confirm the current disinfectant with Poway Public Works at 858-668-4700.

It matters for filters because chloramine is harder to remove than chlorine. Our chloramine post explains why catalytic carbon handles it better than a basic carbon filter.

What happened with Poway's water in 2019?

From November 30 to December 6, 2019, Poway issued a precautionary boil water advisory for the city's roughly 50,000 water customers after storm water backed up into the clearwell, the reservoir that holds treated water at the plant. In January 2020 the State Water Board cited the city, faulting how it communicated with the public during the emergency.

That is the history, and it is fair to know it. The city's own update at the time says residents reported discolored tap water on November 29 and that the advisory was lifted on December 6.

It is also fair to know what came after. Under an agreement with the state Division of Drinking Water, Poway replaced the 1964 clearwell, which had a floating cover, with two new concrete tanks and brought the overflow structure up to industry standards with proper air gaps. According to the city's water infrastructure program page, the new tanks began storing treated water in early July 2026. A new treated-water connection from the San Diego County Water Authority is planned next.

Poway's CY2025 report states that all drinking water quality in the distribution system met or exceeded required standards. In plain terms: the city found the weak point, replaced it, and its latest report shows its water meeting standards.

What about Poway homes on private wells?

Everything above describes city water. Some properties in and around Poway are on private wells, and a private well is not covered by the city's reports at all. Well water can carry iron, manganese, bacteria or other constituents that city water does not, and the only way to know what is in yours is a lab test.

Our East County well water post covers what to test for, how often, and why the test comes before any treatment equipment.

Should you treat Poway's water?

If scale is the problem, yes: at anywhere from about 7 to 17 grains per gallon, Poway's water builds scale on fixtures and water heaters. A softener removes the hardness; a salt-free conditioner keeps it from forming scale but leaves it in the water. If the only complaint is taste, the right carbon filter may be enough.

Softeners are sized on the people in the house times about 75 gallons each per day times your hardness. Poway's swing between years is a reason to size a softener with some headroom rather than to the lowest year on record.

Our salt-free vs softener comparison covers what each system does and does not do, and our cost post covers what each costs installed and to run.