Water hardness in Tacoma
1.9 gpg soft
Tap water in Tacoma is soft: 1.9 gpg (33 mg/L · 1.8 °dH · 3.3 °fH).
Source: Tacoma Water (Tacoma Public Utilities) - 2025 Water Quality Report (2025) · data checked 2026-10-23
Range across supply zones: 18–128 mg/L.
2 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| gpg | mg/L | ||
|---|---|---|---|
| Green River supply (primary source) | 1 | 18 | soft |
| groundwater wells (supplemental) | 2.8 | 48 | soft |
Tacoma Water's main supply is the Green River in the Cascades, treated at the Green River Filtration Facility, with wellfields such as the South Tacoma field used as a supplement. River water from the mountains is soft at 32.9 mg/L CaCO₃ with 2 supply zones; the higher values in the 17.8–128 mg/L range probably reflect well water. Scale is rarely a problem.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 1.9 gpg |
|---|---|
| Calcium (mg/L) | 5.6 |
| Magnesium (mg/L) | 0.93 |
| Utility | Tacoma Public Utilities Water Division |
How Tacoma compares
- Tap water in Tacoma is 79 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 1267 of 1372 in the United States (1 = hardest); 8 % of these cities have softer water.
- In Washington it is number 16 of 27 cities; the regional median is 2.8 gpg.
- Nearest city with clearly softer water: Bellevue, WA, 44 km away (1.4 gpg).
- Nearest city with clearly harder water: Renton, 31 km away (4 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Little or no limescale in kettles, water heaters or washing machines.
- Soap lathers easily; water does not dry skin or hair.
- Dishwasher: salt setting at minimum or off.
- No softener needed; a jug filter only changes taste.
How much salt will you use for softening?
No. Water this soft does not need softening.
Descale a coffee machine or kettle about every 6 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Tacoma
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 2 °dH |
| AEG / Electrolux | 1 |
| Beko | 1st |
| Hoover | S0 |
| LG | H0 |
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 Tacoma water hard or soft?
It is soft: 33 mg/L as CaCO₃ (1.9 gpg, 1.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Tacoma 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 Tacoma water?
1.9 gpg, equal to 1.8 °dH, 3.3 °fH or 33 mg/L calcium carbonate.
What dishwasher salt setting should I use in Tacoma?
For 33 mg/L (1.8 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Tacoma?
No. With soft water a softener adds nothing.
Source
Source: Tacoma Water (Tacoma Public Utilities) - 2025 Water Quality Report (2025). Method: figure published by the water supplier. Tacoma Water (Tacoma Public Utilities) - 2025 Water Quality Report · Outdated figure? Tell us