Tap water in SM1, Sutton2 results are over the limit.Very hard.
Supplied by Thames Water. 74 samples, 23 substances, latest on 31 December 2025. Coliform Bacteria and Nitrite came in above the legal limit. Everything else passed.
7.9 / 10
The tank is as full as the score. The specks are the minerals that make water hard.
What to do about it
Osmio Zero 2.0 Countertop RO
£495typical price
Removes coliform bacteria, the result that stood out in SM1.
Stop the limescale
At 255 mg/L a softener is the only thing that stops limescale. Filters do not soften water.
Osmio PRO-III Ultimate Whole House
£499typical price
Removes coliform bacteria, the result that stood out in SM1.
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What's in a glass of SM1 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 is over its legal limit, at 118% of it.
- Nitrite118%
- Nitrate58%
- Trihalomethanes17%
- Bromate14%
- Arsenic9%
- Lead9%
- Colour9%
- Fluoride9%
- Cadmium8%
- Mercury7%
- Iron7%
- Antimony6%
- Nickel6%
- Boron5%
- Chromium5%
- Aluminium4%
- Copper2%
- Manganese1%
- Selenium1%
- Coliform Bacteria 2 count/100ml found
- E. coli none found
- Conductivity 566 µS/cm
All 23 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Coliform Bacteria | 2 count/100ml | Must be zero | Found |
| Nitrite | 0.59 mg/L | 0.5 mg/L | 118% |
| E. coli | 0 count/100ml | Must be zero | None found |
| Colour | 1.8 mg/L Pt/Co | 20 mg/L Pt/Co | 9% |
| Conductivity | 566 µS/cm | No legal limit | – |
| Fluoride | 0.13 mg/L | 1.5 mg/L | 9% |
| Nitrate | 29 mg/L | 50 mg/L | 58% |
| Hardness (as CaCO3) | 255 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 | 0.0009 mg/L | 0.01 mg/L | 9% |
| Boron | 0.05 mg/L | 1 mg/L | 5% |
| 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 | 0.013 mg/L | 0.2 mg/L | 7% |
| Lead | 0.0009 mg/L | 0.01 mg/L | 9% |
| Manganese | 0.0007 mg/L | 0.05 mg/L | 1% |
| Mercury | 0.00007 mg/L | 0.001 mg/L | 7% |
| Nickel | 0.0011 mg/L | 0.02 mg/L | 6% |
| Selenium | 0.0005 mg/L | 0.04 mg/L | 1% |
| Trihalomethanes | 0.017 mg/L | 0.1 mg/L | 17% |
| Bromate | 0.0014 mg/L | 0.01 mg/L | 14% |
255mg 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 SM1
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Your river is the Beverley Brook (Motspur Park to Thames) and Pyl Brook at West Barnes, rated moderate
The Environment Agency rated the Beverley Brook (Motspur Park to Thames) and Pyl Brook at West Barnes as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by fish, phosphate and insects and other small river life. 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
SM1 in short
Tap water in SM1 (Sutton) is supplied by Thames Water in the Sutton Central zone and scores 7.9 out of 10, against an England and Wales average of 9.0. 2 of 23 tested substances were close to or over a limit. The latest sample is from 31 December 2025.
- Coliform Bacteria detected at 2 per 100 ml, where any amount fails the legal standardAny detection is a failure for this substance. It is one of 2 flagged here. See the full results
- The lowest score of the 6 areas tested in SuttonSM1 scores 7.9 out of 10. The best in Sutton, SM5, scores 8.6.
- Very hard water at 255 mg/LThe threshold for very hard is 250 mg/L. Expect visible limescale on taps and in kettles in SM1. How hardness is measured
Questions about SM1 water
Is SM1 tap water safe to drink?
Based on the latest tests, SM1 (Sutton) water scores 7.9/10, which is safe. 2 of 23 tested contaminants exceeded recommended levels. Water is supplied by Thames Water.
What contaminants are in SM1 water?
We tested 23 contaminants in SM1 water. 2 were flagged, including Coliform Bacteria, Nitrite.
Who supplies water in SM1?
SM1 (Sutton) is supplied by Thames Water. You can view their full profile and compliance data on our supplier page.
Is SM1 water hard or soft?
Water in SM1 (Sutton) has a hardness of 255 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 SM1?
With 2 contaminants above recommended levels in SM1, a water filter could help. A filter jug or under-sink filter can reduce most common contaminants. See our filter recommendations for your area.
Are there PFAS forever chemicals in SM1 water?
No PFAS (forever chemicals) result is attached to the tap-water tests for SM1, and the Environment Agency has no PFAS detections in rivers or groundwater within 10 km of it. That reflects where sampling has happened as much as the water itself.
How clean is the river near SM1?
The Environment Agency rated the Beverley Brook (Motspur Park to Thames) and Pyl Brook at West Barnes as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by fish, phosphate and insects and other small river life. 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 SM1, which is treated before it reaches homes.
Keep reading
- 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
Nitrate levelsHow to test your waterBest water filtersFilter shower headsWater testing kitsUK water rankingsWater hardness checkerWater hardness map
River and groundwater readings near SM1
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.
| Substance | Reading | Drinking water limit |
|---|---|---|
| pH | 7.7 pH | None |
| Temperature | 15.5 °C | None |
| Conductivity | 584 µS/cm | None |
| Nitrate | 3.9 mg/L | 50 mg/L |
| Nitrite | 0.02 mg/L | 0.5 mg/L |
| Phosphate | 0.061 mg/L | None |
| Dissolved Oxygen | 9.21 mg/L | None |
| Ammonia | 0.045 mg/L | 0.5 mg/L |
| Lead | 0.00031 mg/L | 0.01 mg/L |
| Nickel | 0.0023 mg/L | 0.02 mg/L |
| Cadmium | 0.000012 mg/L | 0.005 mg/L |
| Hardness (as CaCO3) | 503 mg/L | None |
| Zinc | 0.018 mg/L | None |
| Copper | 0.00006 mg/L | 2 mg/L |
| Chromium | 0.00016 mg/L | 0.05 mg/L |
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