Tap water in SN25, SwindonSafe to drink.Very hard.
Supplied by Thames Water. 73 samples, 23 substances, latest on 31 December 2025. Everything is inside the legal limit. One result, nitrite, sits close to the line.
8.7 / 10
The tank is as full as the score. The specks are the minerals that make water hard.
What to do about it
Hard water: compare softener quotes
At 272 mg/L a softener is the only thing that stops limescale. Filters do not soften water.
It pays for itself in most homes at this hardness, through a boiler that stays efficient and appliances that last.
Waterdrop G3P600 Reverse Osmosis
£550typical price
Maximum contaminant removal including PFAS and fluoride
Waterdrop 10UA Under Sink
£70typical price
High-volume under-sink filtration without RO complexity
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What's in a glass of SN25 water
Every bubble is a substance the lab measured. The higher it floats, the closer it came to its legal limit, the dashed line at the top.
Nitrite came closest to a limit, at 90% of it. 17 of 19 substances used under a quarter of theirs.
- Nitrite90%
- Nitrate45%
- Trihalomethanes12%
- Lead10%
- Bromate10%
- Fluoride9%
- Colour9%
- Cadmium8%
- Mercury7%
- Arsenic7%
- Nickel7%
- Antimony6%
- Chromium5%
- Aluminium4%
- Iron3%
- Selenium2%
- Boron2%
- Copper2%
- Manganese1%
- Coliform Bacteria none found
- E. coli none found
- Conductivity 483 µS/cm
All 23 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Nitrite | 0.45 mg/L | 0.5 mg/L | 90% |
| Coliform Bacteria | 0 count/100ml | Must be zero | None found |
| E. coli | 0 count/100ml | Must be zero | None found |
| Colour | 1.8 mg/L Pt/Co | 20 mg/L Pt/Co | 9% |
| Conductivity | 483 µS/cm | No legal limit | – |
| Fluoride | 0.14 mg/L | 1.5 mg/L | 9% |
| Nitrate | 22.5 mg/L | 50 mg/L | 45% |
| Hardness (as CaCO3) | 272 mg/L | No legal limit | – |
| Aluminium | 0.0082 mg/L | 0.2 mg/L | 4% |
| Antimony | 0.0003 mg/L | 0.005 mg/L | 6% |
| Arsenic | 0.0007 mg/L | 0.01 mg/L | 7% |
| Boron | 0.02 mg/L | 1 mg/L | 2% |
| Cadmium | 0.0004 mg/L | 0.005 mg/L | 8% |
| Chromium | 0.0025 mg/L | 0.05 mg/L | 5% |
| Copper | 0.03 mg/L | 2 mg/L | 2% |
| Iron | 0.007 mg/L | 0.2 mg/L | 3% |
| Lead | 0.001 mg/L | 0.01 mg/L | 10% |
| Manganese | 0.0006 mg/L | 0.05 mg/L | 1% |
| Mercury | 0.00007 mg/L | 0.001 mg/L | 7% |
| Nickel | 0.0014 mg/L | 0.02 mg/L | 7% |
| Selenium | 0.0009 mg/L | 0.04 mg/L | 2% |
| Trihalomethanes | 0.012 mg/L | 0.1 mg/L | 12% |
| Bromate | 0.001 mg/L | 0.01 mg/L | 10% |
272mg of limescale minerals in every litre
This is the water that furs up kettles
Very hard on the UK scale. It is fine to drink. It is hard on boilers, showers, skin and anything that heats water, and a jug or tap filter will not change that.
Softener quotes for SN25
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Your river is the Haydon Wick Brook, rated moderate
The Environment Agency rated the Haydon Wick Brook as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by dissolved oxygen, insects and other small river life and phosphate. It fails the chemical test, as every river, estuary and stretch of coast in England does, because of long-lasting pollutants such as mercury, PFOS (a forever chemical) and old flame retardants.
None of this is a test of your tap water. Environment Agency record · River health across England
228
forever-chemical detections in nearby rivers and groundwater
At 14 sites. The highest was PFOS (linear) at 0.25 µg/L, at Dudgrove Stream at Gate 7, RAF Fairford, 9.8 km away, in June 2023. These are river and borehole samples, not tests of your tap water.
Every PFAS sample around Swindon · Which filters remove PFAS · PFAS explained
SN25 in short
Tap water in SN25 (Swindon) is supplied by Thames Water in the Swindon Central zone and scores 8.7 out of 10, against an England and Wales average of 9.0. 1 of 23 tested substances was close to or over a limit. The latest sample is from 31 December 2025.
- Nitrite is within its legal limit but flagged, at 90% of the 0.5 mg/L maximumAnything over three quarters of a limit is flagged here as worth watching. It has not gone over. See every reading
- The cleanest tap water of the 8 areas tested in SwindonSN25 scores 8.7 out of 10, ahead of SN1 in second place on 8.6. Every area in Swindon
- Very hard water at 272 mg/LThe threshold for very hard is 250 mg/L. Expect visible limescale on taps and in kettles in SN25. How hardness is measured
Questions about SN25 water
Is SN25 tap water safe to drink?
Based on the latest tests, SN25 (Swindon) water scores 8.7/10, which is safe. 1 of 23 tested contaminants exceeded recommended levels. Water is supplied by Thames Water.
What contaminants are in SN25 water?
We tested 23 contaminants in SN25 water. 1 were flagged, including Nitrite. PFAS (forever chemicals) were also measured in rivers and groundwater within 10 km, though not in the tap-water tests themselves.
Who supplies water in SN25?
SN25 (Swindon) is supplied by Thames Water. You can view their full profile and compliance data on our supplier page.
Is SN25 water hard or soft?
Water in SN25 (Swindon) has a hardness of 272 mg/L CaCO3, which is classified as very hard. Hard water can cause limescale buildup. A water softener or filter jug may help.
Should I use a water filter in SN25?
With 1 contaminant above recommended levels in SN25, a water filter could help. A reverse osmosis or activated carbon filter is recommended for PFAS removal. See our filter recommendations for your area.
Are there PFAS forever chemicals in SN25 water?
The tap-water tests we hold for SN25 do not include a PFAS result. Environment Agency monitoring found PFAS in 228 river and groundwater samples from 14 sites within 10 km of SN25, the highest being PFOS (linear) at 0.25 µg/L about 9.8 km away. These are environmental samples, not tests of tap water. The UK currently has no legal limit for PFAS in drinking water; the Drinking Water Inspectorate uses a 0.1 µg/L guideline for individual compounds. Reverse osmosis filters can reduce PFAS levels.
How clean is the river near SN25?
The Environment Agency rated the Haydon Wick Brook as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by dissolved oxygen, insects and other small river life and phosphate. It fails the chemical test, as every river, estuary and stretch of coast in England does, because of long-lasting pollutants such as mercury, PFOS (a forever chemical) and old flame retardants. This is a rating of the river, not of tap water in SN25, which is treated before it reaches homes.
Keep reading
- Best Filter for PFAS RemovalThe filters with independent certification to remove forever chemicals
- PFAS Forever ChemicalsWhat PFAS are and how to reduce your exposure at home
- Best Water Softener UKHarvey, Kinetico, BWT, Monarch and Water2Buy compared, with real costs
- Do I Need a Water Softener?The hardness bands, the symptoms, and a postcode check
- UK Water Hardness MapIs your water hard or soft, and does it matter?
- Best Water Filters UKEvery filter type compared on what it actually removes
- Do I need a water softener?The hardness bands, the symptoms, and when the answer is no
- Best water softener UKHarvey, Kinetico, BWT, Monarch and Water2Buy compared
- Water softener costUnit, fitting and salt, and how long the payback takes
- Installation explainedWhere it goes, the bypass tap, the drain, DIY or plumber
- Harvey vs KineticoThe two premium twin-cylinder brands, side by side
- Softener salt guideTablet, block or granular, and how much you get through
- Salt-free softenersConditioners and electronic descalers, honestly assessed
PFAS explainedNitrate levelsHow to test your waterBest water filtersFilter shower headsWater testing kitsAll of SwindonUK water rankingsWater hardness checkerWater hardness map
River and groundwater readings near SN25
Environment Agency samples from rivers, groundwater and reservoirs nearby. Not your tap water. For scale they are shown against drinking water limits; rivers are judged against much stricter environmental standards, and on those every river in England fails for chemicals.
Get alerts for your area
We'll email you when water quality data changes for SN25.