Tap water in HP18, 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 283 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 HP18 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.
Fluoride came closest to a limit, at 73% of it. 17 of 19 substances used under a quarter of theirs.
- Fluoride73%
- Nickel28%
- Nitrite14%
- Bromate10%
- Trihalomethanes10%
- Lead9%
- Colour9%
- Iron9%
- Cadmium8%
- Copper8%
- Boron7%
- Mercury7%
- Arsenic7%
- Nitrate6%
- Antimony6%
- Chromium5%
- Aluminium4%
- Manganese4%
- Selenium1%
- Coliform Bacteria none found
- E. coli none found
- Conductivity 569 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 | 569 µS/cm | No legal limit | – |
| Fluoride | 1.1 mg/L | 1.5 mg/L | 73% |
| Nitrate | 3.1 mg/L | 50 mg/L | 6% |
| Nitrite | 0.07 mg/L | 0.5 mg/L | 14% |
| Hardness (as CaCO3) | 283 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 | 0.07 mg/L | 1 mg/L | 7% |
| Cadmium | 0.0004 mg/L | 0.005 mg/L | 8% |
| Chromium | 0.0025 mg/L | 0.05 mg/L | 5% |
| Copper | 0.15 mg/L | 2 mg/L | 8% |
| Iron | 0.017 mg/L | 0.2 mg/L | 9% |
| Lead | 0.0009 mg/L | 0.01 mg/L | 9% |
| Manganese | 0.002 mg/L | 0.05 mg/L | 4% |
| Mercury | 0.00007 mg/L | 0.001 mg/L | 7% |
| Nickel | 0.0056 mg/L | 0.02 mg/L | 28% |
| Selenium | 0.0004 mg/L | 0.04 mg/L | 1% |
| Trihalomethanes | 0.01 mg/L | 0.1 mg/L | 10% |
| Bromate | 0.001 mg/L | 0.01 mg/L | 10% |
283mg 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 HP18
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Your river is the Dorton, Chearsley and Waddesdon Brooks, rated poor
The Environment Agency rated the Dorton, Chearsley and Waddesdon Brooks as poor for ecological health in its 2025 assessment, meaning the river is badly affected, with much of the expected wildlife missing. It is held back by water plants and algae, dissolved oxygen 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
50
forever-chemical detections in nearby rivers and groundwater
At 2 sites. The highest was PFBA at 0.0086 µg/L, at RSN0402 Ds M40, 9.3 km away, in May 2026. These are river and borehole samples, not tests of your tap water.
Every PFAS sample around Oxford · Which filters remove PFAS · PFAS explained
HP18 in short
Tap water in HP18 (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.
- Fluoride is the reading closest to its limit, at 73% of the 1.5 mg/L maximumIt passed with room to spare, and everything else tested sat further below its limit. See every reading
- 3rd cleanest of 26 areas tested in BuckinghamshireOnly 2 areas in Buckinghamshire scored higher. The best is HP19 on 9.3.
- Very hard water at 283 mg/LThe threshold for very hard is 250 mg/L. Expect visible limescale on taps and in kettles in HP18. How hardness is measured
Questions about HP18 water
Is HP18 tap water safe to drink?
Based on the latest tests, HP18 (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 HP18 water?
We tested 23 contaminants in HP18 water. None exceeded recommended safe levels. 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 HP18?
HP18 (Buckinghamshire) is supplied by Thames Water. You can view their full profile and compliance data on our supplier page.
Is HP18 water hard or soft?
Water in HP18 (Buckinghamshire) has a hardness of 283 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 HP18?
HP18 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 HP18 water?
The tap-water tests we hold for HP18 do not include a PFAS result. Environment Agency monitoring found PFAS in 50 river and groundwater samples from 2 sites within 10 km of HP18, the highest being PFBA at 0.0086 µg/L about 9.3 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 HP18?
The Environment Agency rated the Dorton, Chearsley and Waddesdon Brooks as poor for ecological health in its 2025 assessment, meaning the river is badly affected, with much of the expected wildlife missing. It is held back by water plants and algae, dissolved oxygen 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 HP18, 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?
- 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 explainedHow to test your waterBest water filtersFilter shower headsWater testing kitsUK water rankingsWater hardness checkerWater hardness map
River and groundwater readings near HP18
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 HP18.