Tap water in SL8, BuckinghamshireSafe to drink.Very hard.
Supplied by Thames Water. 71 samples, 23 substances, latest on 31 December 2025. Everything is inside the legal limit, and nothing comes close to it.
8.8 / 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 302 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.
ZeroWater 12-Cup Ready-Pour
£40typical price
Households concerned about PFAS and heavy metals
Waterdrop 10UA Under Sink
£70typical price
High-volume under-sink filtration without RO complexity
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What's in a glass of SL8 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 52% of it. 16 of 19 substances used under a quarter of theirs.
- Nitrite52%
- Nitrate26%
- Nickel25%
- Lead12%
- Trihalomethanes11%
- Fluoride11%
- Bromate10%
- Colour9%
- Cadmium8%
- Mercury7%
- Arsenic7%
- Antimony6%
- Chromium5%
- Aluminium4%
- Iron3%
- Boron3%
- Selenium3%
- Copper3%
- Manganese1%
- Coliform Bacteria none found
- E. coli none found
- Conductivity 550 µS/cm
All 23 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| 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 | 550 µS/cm | No legal limit | – |
| Fluoride | 0.16 mg/L | 1.5 mg/L | 11% |
| Nitrate | 12.9 mg/L | 50 mg/L | 26% |
| Nitrite | 0.26 mg/L | 0.5 mg/L | 52% |
| Hardness (as CaCO3) | 302 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 | 0.05 mg/L | 2 mg/L | 3% |
| Iron | 0.007 mg/L | 0.2 mg/L | 3% |
| Lead | 0.0012 mg/L | 0.01 mg/L | 12% |
| Manganese | 0.0006 mg/L | 0.05 mg/L | 1% |
| Mercury | 0.00007 mg/L | 0.001 mg/L | 7% |
| Nickel | 0.0051 mg/L | 0.02 mg/L | 25% |
| Selenium | 0.0012 mg/L | 0.04 mg/L | 3% |
| Trihalomethanes | 0.011 mg/L | 0.1 mg/L | 11% |
| Bromate | 0.001 mg/L | 0.01 mg/L | 10% |
302mg 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 SL8
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Your river is the Thames (Reading to Cookham), rated moderate
The Environment Agency rated the Thames (Reading to Cookham) 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 temperature. 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
SL8 in short
Tap water in SL8 (Buckinghamshire) is supplied by Thames Water in the Buckinghamshire Central zone and scores 8.8 out of 10, against an England and Wales average of 9.0. None of the 23 tested substances came close to a limit. The latest sample is from 31 December 2025.
- Among the hardest water in the country at 302 mg/LVery hard starts at 250 mg/L. At this level kettles scale up within weeks and a softener is a normal purchase in SL8. How hardness is measured
- 4th cleanest of 26 areas tested in BuckinghamshireOnly 3 areas in Buckinghamshire scored higher. The best is HP19 on 9.3.
- Nitrite is the reading closest to its limit, at 52% of the 0.5 mg/L maximumIt passed with room to spare, and everything else tested sat further below its limit. See every reading
Questions about SL8 water
Is SL8 tap water safe to drink?
Based on the latest tests, SL8 (Buckinghamshire) water scores 8.8/10, which is safe. 0 of 23 tested contaminants exceeded recommended levels. Water is supplied by Thames Water.
What contaminants are in SL8 water?
We tested 23 contaminants in SL8 water. None exceeded recommended safe levels.
Who supplies water in SL8?
SL8 (Buckinghamshire) is supplied by Thames Water. You can view their full profile and compliance data on our supplier page.
Is SL8 water hard or soft?
Water in SL8 (Buckinghamshire) has a hardness of 302 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 SL8?
SL8 water scored 8.8/10 with no contaminants above recommended levels. A filter is optional but can improve taste, especially if you notice a chlorine flavour. See our filter recommendations for your area.
Are there PFAS forever chemicals in SL8 water?
No PFAS (forever chemicals) result is attached to the tap-water tests for SL8, 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 SL8?
The Environment Agency rated the Thames (Reading to Cookham) 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 temperature. 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 SL8, 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?
- Is UK Tap Water Safe?Everything you need to know about tap water safety in the UK
- 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
How to test your waterBest water filtersFilter shower headsWater testing kitsUK water rankingsWater hardness checkerWater hardness map
River and groundwater readings near SL8
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 |
|---|---|---|
| Iron | 0.755 mg/L | 0.2 mg/L |
| pH | 8.02 pH | None |
| Temperature | 17.3 °C | None |
| Conductivity | 721 µS/cm | None |
| Nitrate | 8.4 mg/L | 50 mg/L |
| Nitrite | 0.013 mg/L | 0.5 mg/L |
| Phosphate | 0.23 mg/L | None |
| Dissolved Oxygen | 9.71 mg/L | None |
| Ammonia | 0.05 mg/L | 0.5 mg/L |
| Hardness (as CaCO3) | 271 mg/L | None |
| Fluoride | 0.084 mg/L | 1.5 mg/L |
| Chromium | 0.0005 mg/L | 0.05 mg/L |
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