Water hardness in Seongju
103 mg/L moderately hard
Tap water in Seongju is moderately hard: 103 mg/L (6 gpg · 5.7 °dH · 10.3 °fH).
Source: K-water / 경상북도 성주군 via data.go.kr (2025) · data checked 2026-10-20
Range across supply zones: 54–152 mg/L.
The municipal treatment plants serving Seongju had a 2025 median hardness of 102.5 mg/L CaCO₃, with plants ranging from 53.5 to 151.5 mg/L. The region is mostly in the Nakdong River basin, fed by dams such as Andong, Imha and Hapcheon; this utility's own source is not confirmed here. At this level a white film forms on kettles and shower screens, and water heaters collect scale slowly over the years. The spread between plants is wide, so check which plant serves your street.
Korean waterworks report hardness (경도) in mg/L CaCO₃; the drinking-water standard is 300 mg/L (1,000 mg/L for some sources).
Water data
| Total hardness | 103 mg/L |
|---|---|
| Utility | Seongju-gun (경상북도 성주군) |
How Seongju compares
- Tap water in Seongju is 80 % harder than the median of the 127 cities we track in South Korea (57 mg/L).
- By hardness it ranks 13 of 127 in South Korea (1 = hardest); 90 % of these cities have softer water.
- In Gyeongsangbuk-do it is number 3 of 20 cities; the regional median is 66 mg/L.
- Nearest city with clearly softer water: Goryeong, 19 km away (60 mg/L).
- Nearest city with clearly harder water: Goesan, 104 km away (133 mg/L).
Ranking of the hardest and softest water in South Korea →
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 Seongju
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 6 °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 Seongju water hard or soft?
It is moderately hard: 103 mg/L as CaCO₃ (6 gpg, 5.7 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Seongju safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Korean waterworks report hardness (경도) in mg/L CaCO₃; the drinking-water standard is 300 mg/L (1,000 mg/L for some sources).
How many grains per gallon is Seongju water?
6 gpg, equal to 5.7 °dH, 10.3 °fH or 103 mg/L calcium carbonate.
What dishwasher salt setting should I use in Seongju?
For 103 mg/L (5.7 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Seongju?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: K-water / 경상북도 성주군 via data.go.kr (2025). Method: figure published by the water supplier. K-water / 경상북도 성주군 via data.go.kr · Outdated figure? Tell us