The City of Covina's 2025 water quality report puts average hardness at 230 mg/L, about 13.5 grains per gallon. That is very hard water, and it is the main reason Covina water heaters and faucets scale up.
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Written and fact-checked by John, editor, MBA in marketing
Updated against City, utility and state sources
Covina tap water from the City of Covina Water Division averaged 230 mg/L of hardness in 2025, about 13.5 grains per gallon, with a range of 190 to 280 mg/L. The USGS calls anything over 180 mg/L very hard. Golden State Water's San Dimas system averaged about 205 mg/L, or 12 grains. Six suppliers serve Covina, so check the name on your bill first.
Covina is served by six different water suppliers, and the name printed on your water bill tells you which one delivers your water.
Many people assume the City of Covina supplies every tap in town. It does not. The City's own list of water purveyors names six suppliers that serve addresses inside Covina. Two homes on the same side of town can get water from different companies, with different source water, different test results and different phone numbers. That is why this guide starts with the bill, not the hardness number.
The City publishes a service area map with that list, but the map does not read cleanly as text and we will not guess at boundaries street by street. Your bill, your meter lid or a call to the supplier settles it in a minute. Renters can ask the landlord or property manager, who pays that bill.
| Supplier | Office | Phone (plain text) | Hardness data on this page |
|---|---|---|---|
| City of Covina Water Division | 534 N Barranca Ave, Covina | 626-384-5220 | Yes, from the City's 2025 Consumer Confidence Report |
| Suburban Water Systems | 1325 N Grand Ave, Suite 100, Covina | 626-543-2640 | No, read Suburban's own report |
| Golden State Water (San Dimas system) | 115 to 121 Exchange Pl, San Dimas | 800-999-4033 | Yes, from Golden State's San Dimas report |
| Valencia Heights Water Company | 3009 E Virginia Ave, West Covina | 626-332-8935 | No, ask Valencia Heights |
| Azusa Light & Water | 729 N Azusa Ave, Azusa | 626-812-5063 | No, read Azusa's report |
| City of Glendora Water | 1051 E Sierra Madre Ave, Glendora | 626-852-4838 | No, read Glendora's report |
The City of Covina Water Division is the largest of the six inside the city. Its own page says it serves about 33,300 people through about 8,500 service connections, with about 102 miles of water mains, about 1,000 fire hydrants and nine reservoirs holding a combined 20 million gallons. Covina's 2020 Census population was 51,268, so roughly a third of residents get water from someone other than the City.
For contacts beyond water quality (billing, outages, sewer, gas), our who to call guide for Covina puts every number in one table.
The City's 2025 Consumer Confidence Report lists average hardness at 230 mg/L as calcium carbonate, with a range of 190 to 280 mg/L, which works out to about 13.5 grains per gallon.
Every public water system in California has to publish a yearly Consumer Confidence Report, usually called the CCR or water quality report. We opened the City of Covina's report for calendar year 2025 and copied the numbers below from its tables. The report says the water met all state and federal drinking water standards.
The City's main supply comes from Covina Valley Water Company, which filters surface water from the San Gabriel River and disinfects it with chlorine or chloramine plus ultraviolet light. (The City's water page calls the same supplier Covina Irrigating Company.) In February, March, June, September, October and November of 2025, the City also took imported surface water from the Metropolitan Water District's Weymouth treatment plant, which uses ozone as its main disinfectant.
| Constituent | Average | Range | Why a plumber cares |
|---|---|---|---|
| Total hardness (mg/L as CaCO3) | 230 | 190 to 280 | Scale in water heaters, valves and aerators |
| Total hardness (grains per gallon) | About 13.5 | About 11.1 to 16.4 | The unit softener makers use |
| Calcium (mg/L) | 56 | 43 to 70 | The main scale former in hot water |
| Magnesium (mg/L) | 22 | 19 to 25 | Adds to hardness and scale |
| Sodium (mg/L) | 89 | 78 to 100 | Matters if you add a salt softener |
| Total dissolved solids (mg/L) | 540 | 460 to 620 | White spotting on glass and fixtures |
| Alkalinity as CaCO3 (mg/L) | 110 | 95 to 120 | Works with calcium to form scale when heated |
| Chloride (mg/L) | 92 | 86 to 98 | Below the 500 mg/L secondary standard |
| Sulfate (mg/L) | 180 | 140 to 210 | Below the 500 mg/L secondary standard |
| pH (units) | 8.2 | 8.2 to 8.3 | Slightly alkaline, which favors scale over corrosion |
| Fluoride (mg/L) | 0.7 | 0.5 to 0.8 | Not a plumbing issue; listed for completeness |
The calcium and magnesium numbers line up with the hardness total. Calcium at 56 mg/L counts as about 140 mg/L of hardness, and magnesium at 22 mg/L counts as about 91. Together that is about 230, the same figure the report gives. In plain terms, most of Covina's hardness is calcium, and calcium is the mineral that drops out of hot water and builds up as the white, rock-like crust you see inside a water heater or on a shower head.
Hardness is not a health issue. It is a measure of dissolved minerals. What it does affect is the life of water heaters, tankless heat exchangers, toilet fill valves, faucet cartridges and dishwashers. That is the part this page is about.
The City tested tap water at 32 homes in June 2025, and none of the 32 were above the action level for lead or for copper.
Lead and copper are tested at the kitchen tap of homes, not at the treatment plant, because both metals come mostly from plumbing inside buildings. In the City's June 2025 round, lead was detected in 2 of the 32 samples and copper in 14, but zero homes exceeded the action levels (15 micrograms per liter for lead, 1.3 mg/L for copper). The report says the next round of residential sampling is scheduled for 2028.
The City also completed its required service line inventory and reports that no lead or galvanized service lines requiring replacement were found in its distribution system. That statement covers the City's pipes up to your meter. It does not cover the pipes inside your house, which belong to you.
The City's Housing Element says about two-thirds of Covina homes were built before 1970. Many of those houses were plumbed with galvanized steel supply pipe, which rusts from the inside and narrows over decades, especially with hard water depositing minerals at the same time. If your water runs brown when a tap first opens, or pressure has dropped at every fixture, the pipes inside the house are a more likely cause than the City's water. Our whole-house repiping page covers how galvanized lines are replaced with PEX or copper.
Golden State Water's San Dimas system reported average hardness of about 205 mg/L, or 12 grains per gallon, with a range of about 5 to 18 grains.
Some Covina addresses are on Golden State Water's San Dimas system. Its 2026 report, covering 2025 data, lists hardness at an average of 205 mg/L with a range of 85 to 307 mg/L. In grains that is an average of 12, ranging from about 5 to 18. That range is much wider than the City's because Golden State blends three kinds of water: treated groundwater from the Main San Gabriel Basin, local surface water bought from Covina Valley Water Company, and imported Colorado River and State Water Project water delivered through Metropolitan.
The average is a little softer than the City's, but the top of the range is harder. A home on that system can see noticeably different water from month to month as the blend changes.
| Reading | City of Covina | Golden State, San Dimas system |
|---|---|---|
| Hardness average | 230 mg/L (about 13.5 gpg) | 205 mg/L (about 12 gpg) |
| Hardness range | 190 to 280 mg/L | 85 to 307 mg/L (about 5 to 18 gpg) |
| Sodium average | 89 mg/L | 50 mg/L (range 24 to 100) |
| Total dissolved solids | 540 mg/L (460 to 620) | 370 mg/L (160 to 617) |
| pH | 8.2 (8.2 to 8.3) | 8.0 (7.5 to 8.6) |
| Main sources | Filtered San Gabriel River water, plus MWD Weymouth water in six months of 2025 | Basin groundwater, local surface water and imported water, blended |
We did not find current, clearly labeled hardness figures for the Covina service areas of Suburban, Valencia Heights, Azusa Light & Water or Glendora that we could confirm, so we are not printing any. Each of them publishes its own yearly report. Call the number in the table above and ask for "the hardness for the system that serves my address," or test at the tap using the steps further down.
Divide hardness in mg/L (or ppm) by 17.1 to get grains per gallon, the unit on softener labels and many test kits.
Water reports use milligrams per liter, which for water is the same as parts per million. Softener sizing charts use grains per gallon, written gpg. One grain per gallon equals about 17.1 mg/L. So the City's 230 mg/L divided by 17.1 is about 13.5 grains, and Golden State's 205 mg/L is about 12.
The U.S. Geological Survey uses four general hardness classes, measured as calcium carbonate. The USGS notes these are generally accepted categories, not a legal standard. We added grains and the Covina reference points so you can compare a test strip, a softener brochure and the CCR side by side.
| mg/L as CaCO3 | Grains per gallon | USGS class | Covina reference point |
|---|---|---|---|
| 0 to 60 | 0 to 3.5 | Soft | No Covina average falls here |
| 61 to 120 | 3.6 to 7.0 | Moderately hard | Low end of Golden State's range (85 mg/L, about 5 gpg) |
| 121 to 180 | 7.1 to 10.5 | Hard | Part of Golden State's range |
| More than 180 | More than 10.5 | Very hard | City average 230 mg/L (13.5 gpg); entire City range of 190 to 280; Golden State average 205 mg/L (12 gpg) |
At 12 to 13.5 grains, Covina water builds scale fast: tank heaters fill with sediment, tankless units need regular descaling, and valves, aerators and shower heads clog.
Heat is what turns hardness into a plumbing problem. When water warms up, dissolved calcium carbonate comes out of solution and settles as solid scale. Cold water lines in Covina rarely scale badly. Hot water lines, water heaters and anything that heats water (dishwashers, coffee makers, tankless units) take the hit.
| Fixture | What you notice | What helps |
|---|---|---|
| Tank water heater | Popping or rumbling, slower recovery, sediment when the drain valve is opened, shorter life | Periodic flushing; check the anode rod; plan replacement before the tank leaks |
| Tankless water heater | Scale error codes, temperature swings, lower hot water flow | Descale the heat exchanger on the maker's schedule; install isolation valves |
| Faucet aerators and shower heads | Weak, uneven spray and white crust | Soak in vinegar; replace worn aerators |
| Toilet fill valves and flappers | Running toilet, slow refill, phantom refills at night | Replace the fill valve or flapper |
| Single-handle faucet cartridges | Stiff handle, drips, hot side sticking | Replace the cartridge or the faucet |
| Angle stops and old gate valves | Valves that will not turn or will not fully close | Replace before you need them in an emergency |
| Glass, tile and dishes | White spots that wipe off with vinegar | Squeegee showers; rinse aid; a softener if it bothers you |
The U.S. Department of Energy says tank water heaters typically last 10 to 15 years. Very hard water pushes a tank toward the short end of that range. Sediment settles on the bottom, the burner heats through a layer of rock, and the tank works harder and louder. Flushing a few gallons through the drain valve helps, but on a tank that has never been flushed, an old plastic drain valve can stick open or leak afterward. If that worries you, have a plumber do the first one.
When a tank does need replacing in Covina, the City requires a permit for every replacement under Handout #12, with two seismic straps, a T&P relief drain that runs outside, a sediment trap and, in garages, an 18-inch stand. Our water heater repair and replacement page explains repair versus replace, and the Covina plumbing permit guide covers the counter process.
Tankless units pass water through a narrow heat exchanger, so they are more sensitive to scale than a tank. On 13.5 grain water, skipping descaling is the most common reason we see a tankless unit throw error codes or lose flow. A set of isolation valves makes descaling a quick job. See our tankless water heater page for installs and descaling.
Angi's published estimate for a tank water heater replacement is $600 to $2,500 installed (2025). Its estimate for a tankless installation is $1,404 to $3,901 (2026). These are national ranges, not quotes, and Covina permit requirements can push a job toward the top. Call (626) 746-1970 for an exact quote.
For many Covina homes on 12 to 13.5 grain water, a softener is a reasonable choice, especially with a tankless heater, but it adds salt, upkeep and sodium.
A salt-based softener uses ion exchange to swap calcium and magnesium for sodium. It does stop scale. It also needs a brine tank, regular salt, a drain connection for regeneration, and a spot near the main line. Here is how we think about it with homeowners.
City water already carries an average of 89 mg/L of sodium. A salt softener adds more, roughly in proportion to the hardness it removes, and Covina water has a lot of hardness to remove. Many households keep one unsoftened cold tap at the kitchen sink for drinking and cooking. If sodium is a concern for anyone in your home, ask a doctor before softening drinking water.
Our water softener and filtration page covers sizing to your supplier's tested number, loop placement and permits.
Find your supplier on the bill, read that supplier's yearly report, then confirm with a simple test of cold water at the kitchen tap.
Find the supplier's name. Six companies serve Covina, and their water differs.
City of Covina customers can use the 2025 numbers on this page. Golden State customers can use the San Dimas figures. Everyone else should open their supplier's own report or call the number in the first table.
Use a hardness strip or drop kit on cold water at the kitchen tap after it runs for a minute. Hot water readings can be thrown off by the heater.
Divide mg/L or ppm by 17.1 to get grains, then compare with the USGS table above.
Heavy crust on the shower head, a noisy tank or a tankless scale code tells you how the water is treating your plumbing, whatever the number says.
If your heater is rumbling, your tankless unit keeps faulting or you are pricing a softener, we can look at the whole system and give you a written price before any work starts. Homes in downtown Covina and the older blocks across the 91722 ZIP often still have original valves and galvanized lines that decades of hard water have worn down.
A real person answers 24 hours a day. You get an honest arrival window and a written price before any work starts.
Very hard. The City of Covina's 2025 water report lists average hardness of 230 mg/L, about 13.5 grains per gallon, with a range of 190 to 280 mg/L. The USGS classifies anything over 180 mg/L as very hard.
Check the name on your water bill. Six suppliers serve Covina: City of Covina Water, Suburban Water Systems, Golden State Water, Valencia Heights Water Company, Azusa Light & Water and Glendora Water. Our who to call guide lists each phone number.
The City's main supply is San Gabriel River water filtered by Covina Valley Water Company and disinfected with chlorine or chloramine plus UV light. In six months of 2025 the City also used imported water from Metropolitan's Weymouth plant.
Divide by 17.1. The City of Covina's average of 230 mg/L divided by 17.1 is about 13.5 grains per gallon. Golden State's San Dimas average of 205 mg/L is about 12 grains.
The City's 2025 report says its water met all state and federal standards, and none of 32 homes tested in June 2025 were above the lead or copper action levels. Hardness is a mineral issue, not a health issue.
It can. The Department of Energy says tank heaters typically last 10 to 15 years, and heavy scale pushes them toward the short end. Flushing helps. See our water heater repair page if yours is noisy or slow.
Not required, but often worth considering. At 12 to 13.5 grains, a softener protects tankless heaters and fixtures. It adds sodium and upkeep, so weigh it against flushing and descaling. Our water softener page covers sizing.
The City says its service line inventory found no lead or galvanized service lines needing replacement in its system. Pipes inside your home are separate, and many pre-1970 Covina homes still have galvanized steel supply lines.
Facts on this page come from these public sources, checked November 1, 2026.