Tap water in SP11, Test ValleySafe to drink.Very hard.
Supplied by Southern Water. 30,840 samples, 23 substances, latest on 30 April 2026. Everything is inside the legal limit. One result, nitrate, sits close to the line.
9.2 / 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 355 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
Removes nitrate, the result that stood out in SP11.
Osmio PRO-III Ultimate Whole House
£499typical price
Removes nitrate, the result that stood out in SP11.
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What's in a glass of SP11 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.
Nitrate came closest to a limit, at 79% of it. 18 of 19 substances used under a quarter of theirs.
- Nitrate79%
- Nickel15%
- Colour15%
- Trihalomethanes13%
- Ammonia8%
- Aluminium6%
- Iron5%
- Lead5%
- Mercury4%
- Manganese4%
- Turbidity3%
- Selenium3%
- Copper2%
- Antimony2%
- Nitrite2%
- Arsenic1%
- Bromate1%
- Cadmium<1%
- Chromium<1%
- E. coli none found
- Conductivity 549 µS/cm
- pH 7.4 pH
- Coliform Bacteria none found
All 23 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Nitrate | 39.3 mg/L | 50 mg/L | 79% |
| E. coli | 0 count/100ml | Must be zero | None found |
| Conductivity | 549 µS/cm | No legal limit | – |
| Trihalomethanes | 0.0134 mg/L | 0.1 mg/L | 13% |
| Colour | 3 mg/L Pt/Co | 20 mg/L Pt/Co | 15% |
| Turbidity | 0.13 NTU | 4 NTU | 3% |
| pH | 7.4 pH | No legal limit | – |
| Nitrite | 0.009 mg/L | 0.5 mg/L | 2% |
| Ammonia | 0.039 mg/L | 0.5 mg/L | 8% |
| Aluminium | 0.0113 mg/L | 0.2 mg/L | 6% |
| Iron | 0.00928 mg/L | 0.2 mg/L | 5% |
| Manganese | 0.00178 mg/L | 0.05 mg/L | 4% |
| Copper | 0.0463 mg/L | 2 mg/L | 2% |
| Arsenic | 0.00015 mg/L | 0.01 mg/L | 1% |
| Cadmium | 0.000031 mg/L | 0.005 mg/L | <1% |
| Chromium | 0.00019 mg/L | 0.05 mg/L | <1% |
| Nickel | 0.00309 mg/L | 0.02 mg/L | 15% |
| Lead | 0.00046 mg/L | 0.01 mg/L | 5% |
| Antimony | 0.000097 mg/L | 0.005 mg/L | 2% |
| Selenium | 0.00106 mg/L | 0.04 mg/L | 3% |
| Coliform Bacteria | 0 count/100ml | Must be zero | None found |
| Bromate | 0.00013 mg/L | 0.01 mg/L | 1% |
| Mercury | 0.00004 mg/L | 0.001 mg/L | 4% |
355mg 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 SP11
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Your river is the Anton - Upper, rated good
The Environment Agency rated the Anton - Upper as good for ecological health in its 2025 assessment, meaning the river is only slightly changed from its natural state. 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
SP11 in short
Tap water in SP11 (Test Valley) is supplied by Southern Water in the Test Valley Central zone and scores 9.2 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 30 April 2026.
- Nitrate is within its legal limit but flagged, at 79% of the 50 mg/L maximumAnything over three quarters of a limit is flagged here as worth watching. It has not gone over. See every reading
- Among the hardest water in the country at 355 mg/LVery hard starts at 250 mg/L. At this level kettles scale up within weeks and a softener is a normal purchase in SP11. How hardness is measured
- 3rd cleanest of 5 areas tested in Test ValleySquarely mid-table for Test Valley, between SP10 on 9.4 and SO51 on 9.
Questions about SP11 water
Is SP11 tap water safe to drink?
Based on the latest tests, SP11 (Test Valley) water scores 9.2/10, which is safe. 1 of 23 tested contaminants exceeded recommended levels. Water is supplied by Southern Water.
What contaminants are in SP11 water?
We tested 23 contaminants in SP11 water. 1 were flagged, including Nitrate.
Who supplies water in SP11?
SP11 (Test Valley) is supplied by Southern Water. You can view their full profile and compliance data on our supplier page.
Is SP11 water hard or soft?
Water in SP11 (Test Valley) has a hardness of 355 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 SP11?
With 1 contaminant above recommended levels in SP11, 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 SP11 water?
No PFAS (forever chemicals) result is attached to the tap-water tests for SP11, 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 SP11?
The Environment Agency rated the Anton - Upper as good for ecological health in its 2025 assessment, meaning the river is only slightly changed from its natural state. 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 SP11, 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 SP11
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 SP11.