Water hardness in Monrovia
10.8 gpg very hard
Tap water in Monrovia is very hard: 10.8 gpg (185 mg/L · 10.4 °dH · 18.5 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA1910090 (2026-05) · data checked 2026-10-19
Range across supply zones: 149–272 mg/L.
The Monrovia figure comes from State Water Resources Control Board lab results for the city water department. The median of 10 results from 2023 to 2026, taken at 5 well points, is 185 mg/L as CaCO3 (10.8 gpg), with a range of 149 to 272 mg/L. That is very hard on median. Scale builds steadily on heaters and fixtures.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 10.8 gpg |
|---|---|
| Utility | Monrovia-City, Water Dept. |
How Monrovia compares
- Tap water in Monrovia is 19 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 577 of 1372 in the United States (1 = hardest); 58 % of these cities have softer water.
- In California it is number 140 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Duarte, 3 km away (8.4 gpg).
- Nearest city with clearly harder water: Arcadia, 6 km away (14.2 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How much salt will you use for softening?
Yes. At this hardness a softener pays for itself through appliance life and detergent.
Descale a coffee machine or kettle about every 1 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Monrovia
| Brand | Setting for this water |
|---|---|
| Bosch | H03 |
| Miele | 10 °dH |
| AEG / Electrolux | 2 |
| Beko | 3rd |
| Hoover | S2 |
| LG | H2 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Monrovia water hard or soft?
It is very hard: 185 mg/L as CaCO₃ (10.8 gpg, 10.4 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Monrovia safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
How many grains per gallon is Monrovia water?
10.8 gpg, equal to 10.4 °dH, 18.5 °fH or 185 mg/L calcium carbonate.
What dishwasher salt setting should I use in Monrovia?
For 185 mg/L (10.4 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Monrovia?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA1910090 (2026-05). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA1910090 · Outdated figure? Tell us