Water hardness in San Rafael
5 gpg moderately hard
Tap water in San Rafael is moderately hard: 5 gpg (86 mg/L · 4.8 °dH · 8.6 °fH).
Source: Marin Water 2025 Annual Water Quality Report, p9 Hardness row (2025) · data checked 2026-10-20
Range across supply zones: 47–120 mg/L.
2 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| gpg | mg/L | ||
|---|---|---|---|
| Marin Water supply 1 (softer; column name not printed) | 3.4 | 59 | soft |
| Marin Water supply 2 (harder; column name not printed) | 6.5 | 112 | moderately hard |
Marin Water's 2025 report lists hardness from 47 to 120 mg/L (2.7 to 7.0 gpg) across two zones, and we show the 85.5 mg/L midpoint. Which value applies depends on where your home sits in the system, so check with the utility if you need an exact figure. The water is moderate, so scale appears slowly on fixtures and in kettles.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 5 gpg |
|---|---|
| Utility | Marin Water (Marin Municipal Water District) |
How San Rafael compares
- Tap water in San Rafael is 45 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 1086 of 1372 in the United States (1 = hardest); 21 % of these cities have softer water.
- In California it is number 263 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Berkeley, 24 km away (1.6 gpg).
- Nearest city with clearly harder water: Vallejo, 28 km away (9.3 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Visible kettle scale every few weeks; vinegar or citric acid is enough.
- Water heater and washing machine: some long-term scale; a scale inhibitor slows it.
- Dishwasher: medium salt setting.
- Softener optional; pays off mainly with a gas boiler or tankless heater.
How much salt will you use for softening?
Optional. A scale inhibitor or a small softener protects the heater; soap savings are modest.
Descale a coffee machine or kettle about every 3 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in San Rafael
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 5 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| Hoover | S1 |
| LG | H1 |
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 San Rafael water hard or soft?
It is moderately hard: 86 mg/L as CaCO₃ (5 gpg, 4.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in San Rafael 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 San Rafael water?
5 gpg, equal to 4.8 °dH, 8.6 °fH or 86 mg/L calcium carbonate.
What dishwasher salt setting should I use in San Rafael?
For 86 mg/L (4.8 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in San Rafael?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Marin Water 2025 Annual Water Quality Report, p9 Hardness row (2025). Method: figure published by the water supplier. Marin Water 2025 Annual Water Quality Report, p9 Hardness row · Outdated figure? Tell us