Tap water in CB23, South CambridgeshireSafe to drink.Very hard.
Supplied by Cambridge Water. 8,749 samples, 21 substances, latest on 27 December 2024. Everything is inside the legal limit. One result, nitrate, sits close to the line.
9.1 / 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 330 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 CB23.
Osmio PRO-III Ultimate Whole House
£499typical price
Removes nitrate, the result that stood out in CB23.
We earn a commission if you buy through these links, at no extra cost to you. It never changes which product we put first. How we make money
What's in a glass of CB23 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 82% of it. 18 of 19 substances used under a quarter of theirs.
- Nitrate82%
- Fluoride11%
- Colour10%
- Arsenic10%
- Trihalomethanes10%
- Lead9%
- Nickel8%
- Mercury4%
- Antimony4%
- Boron4%
- Iron4%
- Manganese3%
- Aluminium3%
- Turbidity3%
- Cadmium2%
- Copper2%
- Selenium2%
- Chromium1%
- Nitrite<1%
- Coliform Bacteria none found
- Conductivity 570 µS/cm
All 21 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Nitrate | 40.9 mg/L | 50 mg/L | 82% |
| Colour | 2 mg/L Pt/Co | 20 mg/L Pt/Co | 10% |
| Turbidity | 0.12 NTU | 4 NTU | 3% |
| Coliform Bacteria | 0 count/100ml | Must be zero | None found |
| Conductivity | 570 µS/cm | No legal limit | – |
| Trihalomethanes | 0.00955 mg/L | 0.1 mg/L | 10% |
| Nitrite | 0.004 mg/L | 0.5 mg/L | <1% |
| Aluminium | 0.0061 mg/L | 0.2 mg/L | 3% |
| Iron | 0.0073 mg/L | 0.2 mg/L | 4% |
| Manganese | 0.0017 mg/L | 0.05 mg/L | 3% |
| Copper | 0.04 mg/L | 2 mg/L | 2% |
| Fluoride | 0.167 mg/L | 1.5 mg/L | 11% |
| Arsenic | 0.001 mg/L | 0.01 mg/L | 10% |
| Cadmium | 0.00012 mg/L | 0.005 mg/L | 2% |
| Chromium | 0.0005 mg/L | 0.05 mg/L | 1% |
| Mercury | 0.00004 mg/L | 0.001 mg/L | 4% |
| Nickel | 0.0016 mg/L | 0.02 mg/L | 8% |
| Lead | 0.0009 mg/L | 0.01 mg/L | 9% |
| Antimony | 0.0002 mg/L | 0.005 mg/L | 4% |
| Selenium | 0.0008 mg/L | 0.04 mg/L | 2% |
| Boron | 0.04 mg/L | 1 mg/L | 4% |
330mg of limescale minerals in every litre, typical for the CB area. CB23 has no reading of its own.
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 CB23
Leave your details and we will email you when we can match you with installers who cover CB23. No obligation.
Request a free assessment and we'll come back to you with local installer options for your area.
100%
free, no obligation
shared only with your consent
Your river is the Bourn Brook, rated moderate
The Environment Agency rated the Bourn Brook 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 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
10
forever-chemical detections in nearby rivers and groundwater
At 3 sites. The highest was PFPeA at 0.002 µg/L, at Bar Hill Golf Club B/H, 6.0 km away, in January 2026. These are river and borehole samples, not tests of your tap water.
Every PFAS sample around Cambridge · Which filters remove PFAS · PFAS explained
CB23 in short
Tap water in CB23 (South Cambridgeshire) is supplied by Cambridge Water in the South Cambridgeshire Central zone and scores 9.1 out of 10, against an England and Wales average of 9.0. 1 of 21 tested substances was close to or over a limit. The latest sample is from 27 December 2024.
- Nitrate is within its legal limit but flagged, at 82% 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 330 mg/LVery hard starts at 250 mg/L. At this level kettles scale up within weeks and a softener is a normal purchase across the CB postcode area. How hardness is measured
- 2nd cleanest of 3 areas tested in CambridgeSquarely mid-table for Cambridge, between CB22 on 9.1 and CB24 on 9.1. Every area in Cambridge
Questions about CB23 water
Is CB23 tap water safe to drink?
Based on the latest tests, CB23 (South Cambridgeshire) water scores 9.1/10, which is safe. 1 of 21 tested contaminants exceeded recommended levels. Water is supplied by Cambridge Water.
What contaminants are in CB23 water?
We tested 21 contaminants in CB23 water. 1 were flagged, including Nitrate. 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 CB23?
CB23 (South Cambridgeshire) is supplied by Cambridge Water. You can view their full profile and compliance data on our supplier page.
Is CB23 water hard or soft?
No hardness reading has been published for CB23 itself. Across the CB postcode area the typical value is 330 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 CB23?
With 1 contaminant above recommended levels in CB23, a water filter could help. A reverse osmosis or activated carbon filter is recommended for PFAS removal. See our filter recommendations for your area.
Are there PFAS forever chemicals in CB23 water?
The tap-water tests we hold for CB23 do not include a PFAS result. Environment Agency monitoring found PFAS in 10 river and groundwater samples from 3 sites within 10 km of CB23, the highest being PFPeA at 0.002 µg/L about 6 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 CB23?
The Environment Agency rated the Bourn Brook 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 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 CB23, 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?
- 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
PFAS explainedNitrate levelsHow to test your waterBest water filtersFilter shower headsWater testing kitsAll of CambridgeUK water rankingsWater hardness checkerWater hardness map
River and groundwater readings near CB23
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 CB23.