How hard is the water in Thousand Oaks?

Who supplies water in Thousand Oaks?

The City of Thousand Oaks names four water suppliers serving the Conejo Valley’s homes and businesses, and Calleguas Municipal Water District, the wholesaler, counts all four among its member suppliers. The City’s water operations page puts the number of suppliers inside the city at three, but its providers page lists all four:

• The City’s own water utility, the municipal system that Calleguas lists for central Thousand Oaks. It delivers as much as 15 million gallons a day to over 17,000 residences and businesses.
• California American Water (Cal Am), serving western Thousand Oaks and Newbury Park with treated surface water, all of it purchased from Calleguas.
• California Water Service (Cal Water), serving the eastern areas of the city. Its Westlake district has served the Westlake community inside Thousand Oaks since 1983.
• Camrosa Water District, which supplies a small part of the city, about 1.5 square miles. Most of its roughly 31-square-mile district lies outside Thousand Oaks, about 22 square miles of it in unincorporated Ventura County.

To find the supplier for a particular address, the City’s water providers page links a “Find Your Water Provider” map and a water purveyor map.

Behind all four is one wholesale chain. Calleguas is a member agency of the Metropolitan Water District of Southern California, which provides its supply: mainly State Water Project water from the Feather River watershed in the northern Sierra Nevada, filtered and disinfected at Metropolitan’s Joseph Jensen Filtration Plant in Granada Hills. In 2025, 94 percent of Calleguas’s supply came through the Jensen plant, 5 percent from its own Lake Bard filtration plant and 1 percent from its Las Posas aquifer storage program.

How hard each supplier’s water is

Each supplier’s annual water quality report carries a hardness line. The reports use parts per million (ppm) and milligrams per liter (mg/L) for the same measure: the Jensen plant’s 2025 water appears as 140 ppm in Calleguas’s report and as 140 mg/L in Cal Am’s. Three of the seven print grains per gallon, and Lake Sherwood’s district uses nothing else.

Calleguas’s Lake Bard water runs harder than the Jensen plant’s: 163 ppm (9.53 grains) in the City’s 2024 figures, where it was 2 percent of supply, and 164 mg/L (9.5 grains) in Cal Am’s 2025 report, where it was 5 percent.

The City’s figure is a year older than the rest, from its 2025 report on 2024 data. The Jensen plant supplied 98 percent of the City’s water that year, and Calleguas’s reports put that plant’s water at 148 for 2024 and 140 for 2025.

Why Camrosa’s water is different

Camrosa is the only supplier here whose report lists wells of its own. It runs nine wells besides importing water from Calleguas, and about 55 percent of its 2025 water came from them. Its report lists each source’s hardness separately:

Five of the six local sources average more than 180 ppm, the line above which the U.S. Geological Survey (USGS) calls water very hard. The report gives no single figure for the whole system and doesn’t say which wells or blend reach the Thousand Oaks part of the district, so a household there can ask Camrosa which sources serve its street.

Westlake Village, Agoura Hills, Oak Park and Lake Sherwood

Past the city limits, three other suppliers take over, and their figures sit close to the city’s.

• Agoura Hills and the City of Westlake Village, both in Los Angeles County, get Las Virgenes Municipal Water District water, all of it imported. Its 2025 report puts the water delivered to homes at 142 ppm on average, from 119 to 176, and says that figure, rather than the Jensen plant’s, more closely represents what most homes and businesses receive.
• Oak Park gets Triunfo Water & Sanitation District water, 2.6 million gallons a day for more than 14,000 people. Triunfo prints hardness only for the water it buys (140 ppm for the Jensen plant’s share in 2025) and none for its own system.
• Lake Sherwood gets its water from Ventura County Waterworks District No. 38, through 792 service connections, and all of it from the State Water Project. The district gives hardness in grains per gallon only, averaging 8.3 for 2025 within a range of 8.0 to 9.9.

What counts as hard water?

Hardness measures the magnesium, calcium and carbonate minerals in water, in the words of Cal Water’s report. The USGS notes that the U.S. Environmental Protection Agency has set no legal limit for it; instead there is a generally accepted scale, in milligrams per liter as calcium carbonate. Cal Water prints a different scale, so the same water can carry two labels.

By the USGS scale, 140 is hard; by Cal Water’s, it is moderately hard. The water doesn’t change. The USGS adds that most utilities try to keep water out of the very hard band because of scaling in equipment and the extra soap and synthetic detergent it calls for.

Converting grains per gallon

The City, Cal Am and Lake Sherwood’s district print grains per gallon. The City’s own conversion, 148 ppm to 8.65 grains, works out to about 17.1 mg/L per grain: multiply grains by 17.1 to get mg/L, or divide mg/L by 17.1 to get grains. By that factor, District 38’s 8.3 grains comes to about 142 mg/L and its 8.0–9.9 range to about 137–169, a conversion rather than a figure the district reports.

Hard water, tile, grout and stone

Cal Water’s report and the USGS describe hard water by its buildup. Cal Water says it may lead to mineral buildup in pipes or water heaters, and the USGS links very hard water to scaling in equipment and to needing more soap and detergent. Neither goes room by room, so the practical guidance comes from the people who study and care for the surfaces.

Natural stone has rules of its own. The Natural Stone Institute warns that products containing lemon, vinegar or other acids may dull or etch calcareous stones, which it describes as composed mainly of calcium carbonate, and it doesn’t recommend acidic cleaners for siliceous stone either. For routine cleaning it recommends a neutral cleaner, stone soap, or a mild liquid dishwashing detergent and warm water, and it notes that sealing makes stone more stain resistant, not stain proof.

Grout can be cleaned and then sealed or recolored; HomeAdvisor notes that most grout colorants double as a sealant. Leaf marks on stone entries are a separate problem with their own fix: oak leaf stains on stone.

What a tile and grout cleaning costs

By HomeAdvisor’s national figures, cleaning tile and grout costs $0.50–$3 per square foot, with the tile, the grout and their condition deciding where a job lands. Some companies add a $100–$200 minimum call-out fee, and some price a 150- to 250-square-foot room at a flat $300–$500. Sealing has its own price: Fixr’s figure for a standard grout sealant is $0.90–$1.73 per square foot, and $1.50–$2.50 per square foot when cleaning and sealing are bundled. Recoloring grout runs $1–$2.50 per square foot on HomeAdvisor’s figures.

Maid VIP, our affiliated partner, estimates $0.50–$3 per square foot; kitchens $100–$200, whole homes $350–$600; sealing quoted separately. Independent local professionals do the work, and the cleaning company confirms the price before any work.

Say a bathroom floor and shower add up to 120 square feet. At HomeAdvisor’s $0.50–$3 per square foot that is $60–$360, so at a company with a $100–$200 minimum, the minimum may set the bill. Add rooms at published rates in the visit builder, read what to ask before hiring a cleaner, or ask for a price for tile and grout cleaning.

Sources

Each was opened and checked in October 2026. Prices are national figures or Maid VIP’s labeled estimates, not quotes.

1. City of Thousand Oaks, water providers
2. City of Thousand Oaks, water operations
3. Calleguas Municipal Water District, member purveyors
4. California American Water, Thousand Oaks water quality report (2025 data)
5. California Water Service, Westlake district 2025 water quality report
6. California Water Service, Westlake district
7. Camrosa Water District, 2025 urban water management plan
8. Calleguas Municipal Water District, 2025 annual water quality report
9. City of Thousand Oaks, 2025 annual water quality report (2024 data), State Water Board copy
10. Camrosa Water District, water quality report, reporting year 2025
11. Las Virgenes Municipal Water District, consumer confidence and water quality report, 2025
12. Las Virgenes Municipal Water District, the district
13. Triunfo Water & Sanitation District, 2025 annual water quality report
14. Ventura County Waterworks District No. 38 (Lake Sherwood), water quality report, reporting year 2025, State Water Board copy
15. Calleguas Municipal Water District, annual water quality report (July 2025, 2024 data)
16. U.S. Geological Survey, water hardness in the United States
17. County of Los Angeles, cities within the county
18. Triunfo Water & Sanitation District, water service
19. Natural Stone Institute, cleaning products for natural stone
20. HomeAdvisor, tile and grout cleaning cost (updated June 19, 2026)
21. Fixr, tile and grout cleaning cost (updated January 31, 2025)
22. Maid VIP, tile and grout cleaning (Maid VIP shares owners with this site)