Water hardness in Washington, D.C.
8.1 gpg hard
Tap water in Washington, D.C. is hard: 8.1 gpg (139 mg/L · 7.8 °dH · 13.9 °fH).
Source: DC Water Drinking Water Analysis Data for 2025 (report linked from dcwater.com/waterreport) (2025) · data checked 2026-10-19
Range across supply zones: 84–194 mg/L.
DC Water's 2025 analysis gives a total hardness of 139 mg/L (8.1 gpg), with a range of 84 to 194 mg/L in the report. The supply is treated Potomac River surface water. This is hard water, so expect visible scale on kettles and shower screens.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 8.1 gpg |
|---|---|
| Utility | DC Water (District of Columbia Water and Sewer Authority) |
How Washington, D.C. compares
- Tap water in Washington, D.C. is 10 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 782 of 1372 in the United States (1 = hardest); 43 % of these cities have softer water.
- Nearest city with clearly softer water: Baltimore, 57 km away (5.5 gpg).
- Nearest city with clearly harder water: Alexandria, 11 km away (11.2 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Fast scale on taps, shower screens and kettle; white spots on glassware.
- Water heater: efficiency loss and element failures within years if unprotected.
- Dry skin and dull hair after showering are common.
- Softener recommended; jug or reverse osmosis for drinking.
How much salt will you use for softening?
Recommended, especially with a heater or boiler: scale cuts efficiency and shortens its life.
Descale a coffee machine or kettle about every 2 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Washington, D.C.
| Brand | Setting for this water |
|---|---|
| Bosch | H01 |
| Miele | 8 °dH |
| AEG / Electrolux | 2 |
| Beko | 3rd |
| Hoover | S1 |
| 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 Washington, D.C. water hard or soft?
It is hard: 139 mg/L as CaCO₃ (8.1 gpg, 7.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Washington, D.C. 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 Washington, D.C. water?
8.1 gpg, equal to 7.8 °dH, 13.9 °fH or 139 mg/L calcium carbonate.
What dishwasher salt setting should I use in Washington, D.C.?
For 139 mg/L (7.8 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in Washington, D.C.?
Recommended if you have a water heater, boiler or tankless unit: it saves repairs and detergent.
Source
Source: DC Water Drinking Water Analysis Data for 2025 (report linked from dcwater.com/waterreport) (2025). Method: figure published by the water supplier. DC Water Drinking Water Analysis Data for 2025 (report linked from dcwater.com/waterreport) · Outdated figure? Tell us