Is San Diego water hard? Yes. The City of San Diego says its drinking water typically averages about 16 grains per gallon, or 276 parts per million, and that it can range from 16 to 18 grains per gallon (272 to 284 ppm) depending on water demand and the area of the city where you live.
Grains, ppm and milligrams per liter
Hardness is measured as calcium carbonate, in one of three units. Parts per million and milligrams per liter are the same number for water. Grains per gallon is the unit softener makers use; one grain per gallon is about 17 mg/L. So the city’s 16 grains per gallon and 276 ppm describe the same water.
| USGS grade | mg/L as calcium carbonate | About, in grains per gallon |
|---|---|---|
| Soft | 0 to 60 | 0 to 3.5 |
| Moderately hard | 61 to 120 | 3.5 to 7 |
| Hard | 121 to 180 | 7 to 10.5 |
| Very hard | More than 180 | More than 10.5 |
| City of San Diego, typical | 276 (272 to 284) | About 16 (16 to 18) |
On the US Geological Survey’s scale, more than 180 mg/L is very hard. The city’s typical figure is well past that line. The grains-per-gallon column is a conversion at about 17 mg/L per grain, rounded; the mg/L figures are the USGS’s own.
Who the figure applies to
The city’s figure is for homes served by City of San Diego Public Utilities. Neighborhoods inside the city, such as La Jolla, Pacific Beach, Point Loma, North Park, Clairemont, Mira Mesa and Rancho Bernardo, get their bills from the city if they are on its system; check your bill to be sure. Chula Vista, La Mesa, El Cajon and Poway are separate cities with their own water providers. This site does not print a figure for them: ask your water provider for its annual water quality report. See the areas pages.
What hard water does at home
Hardness comes from calcium and magnesium. USGS notes that soap reacts with the calcium to form soap scum, so more soap or detergent is needed to get things clean. Water utilities commonly add that hard water deposits build up on dishes, fixtures and basins and can cause scale on pipes.
- White spots on glasses, dishes and shower doors
- Crust on faucet aerators and shower heads
- Soap scum in tubs and basins
- Soap and shampoo that lather poorly
Is hard water bad for you?
Utilities say no. Water utilities commonly note that hard water does not pose a health risk, and that there is no health-based drinking water standard for it. Some state it in plain words: hard water is not a health hazard, and hardness is not regulated under drinking water health standards. EPA’s list of secondary standards for taste, color and odor does not list hardness at all. Hard water is a nuisance for cleaning and fixtures, not a safety issue.
What you can do about it
The equipment that removes hardness for the whole house is a water softener. A salt-based softener exchanges calcium and magnesium for sodium in a resin tank; NSF/ANSI 44 is the standard for residential softeners of this kind. A salt-free conditioner is a different technology from ion exchange: ask the installer what it is certified for. A filter does not remove hardness.
- Test the water at your tap, so a softener is sized to your figure, not the city’s average
- See how a softener is sized and permitted on the water softener installation page
- If you already have one and the spots are back, see water softener repair
- Compare salt and salt-free on the water treatment page
Tired of the spots? Send the form and an independent local pro can contact you about a hardness test and a quote.
Questions people ask
How hard is San Diego water?
The City of San Diego says it typically averages about 16 grains per gallon (276 ppm), ranging from 16 to 18 grains per gallon by demand and area.
Is 17 grains per gallon hard water?
Yes. At about 17 mg/L per grain it is roughly 290 mg/L, well over the 180 mg/L at which USGS calls water very hard.
Is San Diego hard water safe to drink?
Utilities say hard water is not a health risk, and there is no health-based standard for hardness. For the city’s water as a whole, read its annual Drinking Water Quality Report.
Does hardness differ across San Diego?
The city says it can range from 16 to 18 grains per gallon depending on demand and the area of the city. A test at your tap gives your own figure.
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