Tap water in SM5, SuttonNitrite is over the limit.Very hard.
Supplied by Thames Water. 73 samples, 23 substances, latest on 31 December 2025. Nitrite came in above the legal limit. Everything else passed.
8.6 / 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 313 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.
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What's in a glass of SM5 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 104% of it.
- Nitrite104%
- Nitrate52%
- Bromate10%
- Lead9%
- Colour9%
- Cadmium8%
- Mercury7%
- Arsenic7%
- Fluoride7%
- Antimony6%
- Chromium5%
- Trihalomethanes5%
- Nickel5%
- Aluminium4%
- Iron3%
- Boron3%
- Copper3%
- Selenium2%
- Manganese1%
- Coliform Bacteria none found
- E. coli none found
- Conductivity 590 µS/cm
All 23 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Nitrite | 0.52 mg/L | 0.5 mg/L | 104% |
| 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 | 590 µS/cm | No legal limit | – |
| Fluoride | 0.1 mg/L | 1.5 mg/L | 7% |
| Nitrate | 26.2 mg/L | 50 mg/L | 52% |
| Hardness (as CaCO3) | 313 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 | 0.03 mg/L | 1 mg/L | 3% |
| Cadmium | 0.0004 mg/L | 0.005 mg/L | 8% |
| Chromium | 0.0025 mg/L | 0.05 mg/L | 5% |
| Copper | 0.06 mg/L | 2 mg/L | 3% |
| Iron | 0.007 mg/L | 0.2 mg/L | 3% |
| Lead | 0.0009 mg/L | 0.01 mg/L | 9% |
| Manganese | 0.0006 mg/L | 0.05 mg/L | 1% |
| Mercury | 0.00007 mg/L | 0.001 mg/L | 7% |
| Nickel | 0.0009 mg/L | 0.02 mg/L | 5% |
| Selenium | 0.0009 mg/L | 0.04 mg/L | 2% |
| Trihalomethanes | 0.005 mg/L | 0.1 mg/L | 5% |
| Bromate | 0.001 mg/L | 0.01 mg/L | 10% |
313mg 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 SM5
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Your river is the Wandle (Croydon to Wandsworth) and the Graveney, rated moderate
The Environment Agency rated the Wandle (Croydon to Wandsworth) and the Graveney as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by phosphate and fish. 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
SM5 in short
Tap water in SM5 (Sutton) is supplied by Thames Water in the Sutton Central zone and scores 8.6 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 was measured at 0.52 mg/L, 4% over the UK limitIt is the only one of 23 tested substances to go over its limit. See the full results
- The cleanest tap water of the 6 areas tested in SuttonSM5 scores 8.6 out of 10, ahead of SM2 in second place on 8.5.
- Among the hardest water in the country at 313 mg/LVery hard starts at 250 mg/L. At this level kettles scale up within weeks and a softener is a normal purchase in SM5. How hardness is measured
Questions about SM5 water
Is SM5 tap water safe to drink?
Based on the latest tests, SM5 (Sutton) water scores 8.6/10, which is safe. 1 of 23 tested contaminants exceeded recommended levels. Water is supplied by Thames Water.
What contaminants are in SM5 water?
We tested 23 contaminants in SM5 water. 1 were flagged, including Nitrite.
Who supplies water in SM5?
SM5 (Sutton) is supplied by Thames Water. You can view their full profile and compliance data on our supplier page.
Is SM5 water hard or soft?
Water in SM5 (Sutton) has a hardness of 313 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 SM5?
With 1 contaminant above recommended levels in SM5, 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 SM5 water?
No PFAS (forever chemicals) result is attached to the tap-water tests for SM5, 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 SM5?
The Environment Agency rated the Wandle (Croydon to Wandsworth) and the Graveney as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by phosphate and fish. 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 SM5, 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 SM5
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 SM5.