Tap water in CO5, ColchesterSafe to drink.Very hard.
Supplied by Anglian Water. 1,644 samples, 22 substances, latest on 27 December 2024. Everything is inside the legal limit, and nothing comes close to it.
9.3 / 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 282 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 CO5 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 31% of it. 18 of 19 substances used under a quarter of theirs.
- Fluoride31%
- Trihalomethanes19%
- Nitrate17%
- Nickel15%
- Iron11%
- Copper7%
- Bromate7%
- Aluminium6%
- Manganese6%
- Nitrite6%
- Mercury6%
- Boron6%
- Antimony6%
- Turbidity5%
- Arsenic2%
- Selenium2%
- Lead2%
- Chromium2%
- Cadmium<1%
- Coliform Bacteria none found
- E. coli none found
- Conductivity 508 µS/cm
All 22 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Aluminium | 0.012 mg/L | 0.2 mg/L | 6% |
| Copper | 0.14 mg/L | 2 mg/L | 7% |
| Fluoride | 0.47 mg/L | 1.5 mg/L | 31% |
| Arsenic | 0.00019 mg/L | 0.01 mg/L | 2% |
| Cadmium | 0.00002 mg/L | 0.005 mg/L | <1% |
| Chromium | 0.00076 mg/L | 0.05 mg/L | 2% |
| Nickel | 0.00307 mg/L | 0.02 mg/L | 15% |
| Lead | 0.00016 mg/L | 0.01 mg/L | 2% |
| Antimony | 0.00028 mg/L | 0.005 mg/L | 6% |
| Selenium | 0.00072 mg/L | 0.04 mg/L | 2% |
| Coliform Bacteria | 0 count/100ml | Must be zero | None found |
| E. coli | 0 count/100ml | Must be zero | None found |
| Turbidity | 0.21 NTU | 4 NTU | 5% |
| Iron | 0.021 mg/L | 0.2 mg/L | 11% |
| Manganese | 0.003 mg/L | 0.05 mg/L | 6% |
| Nitrate | 8.37 mg/L | 50 mg/L | 17% |
| Nitrite | 0.03 mg/L | 0.5 mg/L | 6% |
| Trihalomethanes | 0.0192 mg/L | 0.1 mg/L | 19% |
| Conductivity | 508 µS/cm | No legal limit | – |
| Mercury | 0.00006 mg/L | 0.001 mg/L | 6% |
| Boron | 0.06 mg/L | 1 mg/L | 6% |
| Bromate | 0.0007 mg/L | 0.01 mg/L | 7% |
282mg 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 CO5
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Your river is the Layer Brook, rated poor
The Environment Agency rated the Layer Brook 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 dissolved oxygen, insects and other small river life and water plants and algae. 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
CO5 in short
Tap water in CO5 (Colchester) is supplied by Anglian Water in the Colchester Central zone and scores 9.3 out of 10, against an England and Wales average of 9.0. None of the 22 tested substances came close to a limit. The latest sample is from 27 December 2024.
- The cleanest tap water of the 6 areas tested in ColchesterCO5 scores 9.3 out of 10, ahead of CO6 in second place on 9.3.
- Very hard water at 282 mg/LThe threshold for very hard is 250 mg/L. Expect visible limescale on taps and in kettles in CO5. How hardness is measured
- Nothing tested came within 40% of its legal limitThe highest was Fluoride at 31% of the 1.5 mg/L maximum. See every reading
Questions about CO5 water
Is CO5 tap water safe to drink?
Based on the latest tests, CO5 (Colchester) water scores 9.3/10, which is safe. 0 of 22 tested contaminants exceeded recommended levels. Water is supplied by Anglian Water.
What contaminants are in CO5 water?
We tested 22 contaminants in CO5 water. None exceeded recommended safe levels.
Who supplies water in CO5?
CO5 (Colchester) is supplied by Anglian Water. You can view their full profile and compliance data on our supplier page.
Is CO5 water hard or soft?
Water in CO5 (Colchester) has a hardness of 282 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 CO5?
CO5 water scored 9.3/10 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 CO5 water?
No PFAS (forever chemicals) result is attached to the tap-water tests for CO5, 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 CO5?
The Environment Agency rated the Layer Brook 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 dissolved oxygen, insects and other small river life and water plants and algae. 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 CO5, 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 CO5
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 CO5.