Water hardness in Holywood
31 mg/L soft
Tap water in Holywood is soft: 31 mg/L (1.8 gpg · 1.7 °dH · 3.1 °fH).
Source: NI Water, customer tap results 2024,2025 (OpenDataNI, OGL v3.0) (2025-11) · data checked 2026-10-19
Range across supply zones: 22–39 mg/L.
The tap water in Holywood is provided by NI Water from one of its 24 treatment works, treating lough, river or reservoir water rather than groundwater. Reported hardness is 30.7 mg/L CaCO₃, ranging from 22.2 to 39.2 mg/L between supply zones. Sources fed by hard upland rock and peaty catchments carry little dissolved calcium; scale is modest in kettles and showers, and most households manage without a softener.
UK suppliers report mg/L CaCO₃ and often Clark degrees (1 °Clark = 14.25 mg/L).
Water data
| Total hardness | 31 mg/L |
|---|---|
| Utility | Northern Ireland Water |
How Holywood compares
- Tap water in Holywood is 83 % softer than the median of the 471 cities we track in the United Kingdom (185 mg/L).
- By hardness it ranks 429 of 471 in the United Kingdom (1 = hardest); 9 % of these cities have softer water.
- In Northern Ireland it is number 87 of 110 cities; the regional median is 100 mg/L.
- Nearest city with clearly softer water: Bangor, 10 km away (23 mg/L).
- Nearest city with clearly harder water: Newtownabbey, 6 km away (147 mg/L).
Ranking of the hardest and softest water in the United Kingdom →
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 Holywood
| 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 Holywood water hard or soft?
It is soft: 31 mg/L as CaCO₃ (1.8 gpg, 1.7 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Holywood safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. UK suppliers report mg/L CaCO₃ and often Clark degrees (1 °Clark = 14.25 mg/L).
How many grains per gallon is Holywood water?
1.8 gpg, equal to 1.7 °dH, 3.1 °fH or 31 mg/L calcium carbonate.
What dishwasher salt setting should I use in Holywood?
For 31 mg/L (1.7 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Holywood?
No. With soft water a softener adds nothing.
Source
Source: NI Water, customer tap results 2024,2025 (OpenDataNI, OGL v3.0) (2025-11). Method: own measurement. NI Water, customer tap results 2024,2025 (OpenDataNI, OGL v3.0) · Outdated figure? Tell us