How Hard Is the Water on the LA Westside? The Actual Numbers

What does each Westside utility report for hardness?

Each utility reports a different number. LADWP and Santa Monica report about 103 mg/L (6 grains), Golden State Water's Culver City System 203 mg/L (12 grains), and Inglewood's sources 190 to 274 mg/L (11 to 16 grains).

Every figure below is the utility's own, for the year shown. Where a utility does not publish one number for an area, we say so instead of guessing.

Marina del Rey is the one blank. LA County Waterworks District No. 29, which serves the marina, reports hardness separately for the two Metropolitan Water District treatment plants that supply it, and does not publish a figure for the marina itself. The only honest way to know that number is to test at the tap.

Why does hardness change from one Westside block to the next?

Because the water comes from different places. Los Angeles Aqueduct water is softer, imported Metropolitan Water District water is harder, and each utility uses a different mix.

LADWP serves Westchester and Venice from its Los Angeles Aqueduct Filtration Plant. LADWP's report says that in 2025 the Los Angeles Aqueduct supplied 44 percent of the city's water and purchased Metropolitan Water District water supplied 52 percent. Aqueduct water carries fewer minerals, so the blend comes in around 103 mg/L.

Santa Monica gets up to 75% of its water from its own groundwater wells and softens it with reverse osmosis at the Arcadia plant before it is distributed. That treated groundwater measured 103 mg/L in 2025. The rest of the city's supply is purchased from MWD.

Golden State Water's Culver City System delivers only imported MWD water from the Colorado River Aqueduct and the State Water Project, with no aqueduct water in the mix, which is why it reports about twice LADWP's figure. Inglewood pumps its own well water, which its 2025 report puts at 274 mg/L, and blends it with imported water at 203 mg/L.

Imported water also changes from year to year. MWD's Jensen plant measured 270 mg/L in 2024 and 140 mg/L in 2025. That is why any number on this page is the most recent published year, not a permanent fact about your house.

Why doesn't the 14 grains per gallon figure apply here?

Because it describes other treatment plants. Figures near 14 grains come from MWD's Weymouth and Diemer plants, which LADWP's report assigns to its Harbor and Eastern Los Angeles customers, not to its Westside customers.

LADWP's 2025 report has a single table with a column for each source. It tells Western Los Angeles customers to read the Los Angeles Aqueduct Filtration Plant column, and Harbor and Eastern Los Angeles customers to read the MWD Weymouth, Diemer and Jensen columns. The Weymouth and Diemer columns average 234 and 236 mg/L, about 13.7 and 13.8 grains per gallon. Those are the numbers that end up on water softener websites as the Los Angeles figure.

They are accurate for the parts of the city that receive that water. Applied to a house in Westchester or Venice, they overstate the hardness by more than double.

Water from those plants does reach some Westside systems that buy from MWD. LA County's district for Marina del Rey lists both the Jensen and Weymouth plants, and Santa Monica buys MWD water to top up its own wells. That is part of why those areas vary more, and why a test at your tap beats any single published number.

Does 6 grains per gallon count as hard water?

It counts as moderately hard. The USGS classifies 61 to 120 mg/L as moderately hard, 121 to 180 as hard, and anything above 180 as very hard.

On the USGS scale, the Westside spans moderately hard to very hard.

What should you do with your number?

Match the treatment to the number. Near 6 grains, start with carbon filtration and reverse osmosis for taste and drinking water; from 11 to 16 grains, a water softener belongs in the first conversation.

At 6 grains, the complaint we hear most is the taste and smell of the disinfectant, not scale. That is a job for carbon, and our post on chlorine, chloramine and taste explains what carbon does and does not remove. In Westchester, Venice and Santa Monica a softener is a second step, only for homes with a specific scale problem.

At 12 to 16 grains, scale is a real cost: water heaters fill with sediment and fixtures crust over. In Culver City and Inglewood, a softener is often the first purchase, paired with carbon for taste. In Marina del Rey, where most people rent, the starting point is usually under-sink reverse osmosis.

Whatever your area, test at your own tap before you buy anything, because a utility's own range can be wide. Our guide to reading your water quality report shows where to find each utility's figures.