Lisburn Water Hardness & Quality Report (2026)
Water Hardness
2.6°Clark3.7°fH2°dH
Source
reservoir
pH Level
7.2
neutral = 7.0
Lead
0.001 mg/L
✓ Below action level
TDS
60.9 mg/L
Est. Daily Cost
£0.08
energy & soap waste
Source: DWI Data Portal · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In Lisburn, your appliances are currently losing 5% efficiency due to mineral buildup.
| Appliance | In Lisburn | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 8.4 yrs | 8.5 yrs | -1% |
| Washing Machine | 12.2 yrs | 12 yrs | — |
| Water Heater | 14.1 yrs | 15 yrs | -6% |
Regional Water Comparison
How Lisburn compares to its nearest neighbours
| City | Hardness | Clark° | Risk | Source |
|---|---|---|---|---|
| ▶ Lisburn, Northern Ireland | 36.5 mg/L | 2.6° | 🟢 Soft | reservoir |
| Belfast, Northern Ireland | 70 mg/L | 4.9° | 🟡 Moderately Hard | reservoir |
| Castlereagh, Northern Ireland | 110 mg/L | 7.7° | 🟡 Moderately Hard | reservoir |
| Newtownabbey, Northern Ireland | 155 mg/L | 10.9° | 🟠 Hard | reservoir |
| Holywood, Northern Ireland | 154.5 mg/L | 10.8° | 🟠 Hard | reservoir |
National Benchmark
How Lisburn compares to the United Kingdom average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Lisburn | 36.5 mg/L | 🟢 None |
| United Kingdom National Avg | 183 mg/L | 🔴 High |
| Livingston Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Lisburn's Water Unique?
Local geology and source profile
Lisburn, in the Lisburn and Castlereagh council area south of Belfast, is supplied by NI Water from the Silent Valley and Ben Crom Reservoirs in the Mourne Mountains of south Down. The Mourne Mountain catchment is formed from hard, impermeable Mourne Granite and ancient Silurian greywacke — coarse clastic sedimentary rocks that are almost entirely calcium-free. Rainfall on the Mourne summits (among the highest in Ireland) drains quickly over granite and greywacke bedrock, accumulating virtually no dissolved minerals before entering Silent Valley and Ben Crom. NI Water conveys the Mourne supply northward via the Silent Valley Aqueduct through the Castlereagh hills to Belfast and the greater Belfast metropolitan area, including Lisburn. Water is treated at NI Water's Drumaroad facility before distribution.
Lisburn's very soft water — 36.5 mg/L (2.6°Clark) — is a direct consequence of the Mourne Granite catchment. The Mourne Mountains are underlain by the Newry Granites — a suite of Caledonian-age granitic intrusions dating from around 400 million years ago — which are highly insoluble and yield almost calcium-free runoff. This makes the Mourne supply one of the softest in the United Kingdom. The Drinking Water Quality Regulator for Northern Ireland classifies this supply as very soft, with calcium hardness well below 50 mg/L.
Limescale is virtually absent in Lisburn homes. At 36.5 mg/L, the water is so soft that kettles and appliances require descaling only once or twice a year, and glass shower screens and taps remain largely clear of deposits. Washing-up liquid lathers exceptionally well with very soft water. However, very soft water can be mildly corrosive to copper pipes — older Lisburn properties with legacy copper plumbing may benefit from a pH neutralisation filter or an occasional plumbing inspection to check for corrosion in ageing pipework.
Geology & Source: Supplied by NI Water from the Mourne Mountains reservoir system — Lisburn's location south of Belfast draws on NI Water's granite and schist upland reservoirs in the Mournes, producing very soft water at 36.5 mg/L (2.6°Clark).