London and the Thames Valley

Thames Water: water quality and hardness

Thames Water supplies drinking water and operates wastewater services. The two service areas are not identical: a Thames wastewater bill does not by itself confirm that Thames supplies your drinking water.

An independent WaterGrade guide. Local readings vary by source area and date.

Restrictions: Check the current hosepipe ban status for Thames Water

Find the water serving your home

This checks the supplying area; it does not assume this company serves every postcode you enter.

How Thames Water reports on your water

Its water-quality programme samples the network and customers’ taps. Local annual reports are more useful for understanding your supply than a headline company-wide compliance percentage.

Use the official postcode search to find your supply-area report. Check the year printed in the PDF and keep the source-area name when comparing editions.

Company information and source context ↗

What WaterGrade currently holds

Named areas with records: 245
Areas with measured hardness: 245
Areas with other quality data: 245
Areas with annual hardness history: 71

These count our verified records, including historical areas. They are not the company’s current total zones, population coverage or a quality score.

Our approved annual PDFs include historical editions for some areas. These are area summaries; the postcode checker confirms the supplier’s area association.

Is the water hard or soft?

Check the figure for your supply zone. A company can deliver water from different sources, so a single average can give the wrong appliance setting for your home. Hardness describes dissolved minerals; it is not a safety rating.

Our local cards use mg/l as calcium carbonate (CaCO₃). Keep the original unit and reporting period when comparing results. Supplier labels can use different hardness bands.

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What do the quality results tell you?

Read each parameter with its units, sample count, range and reporting period. A mean below a reference limit does not establish that every sample complied. A “less than” result is not an exact concentration.

Company-wide performance, local zone results and water at an individual tap are different levels of information. Historical exceedances need the supplier’s investigation context; they are not automatically a current incident.

Understand the measurements in a water report

One named-area example · not a company average

Inside the ABBEY WOOD report

262 mg/l as CaCO₃ · hardness period: 2024

Quality reporting period: 2024. 24 parameters in this publication. Hardness may come from a separate source and period.

This is a retained approved report. A source update is awaiting review. Check the original supplier report for more recent information.

Selected source measurements for ABBEY WOOD
Parameter	Published mean	Samples
Hydrogen Ion	7.7 pH units	53
Chlorine (Residual)	0.44 mg/l	195
Nitrate as NO3	25 mg/l	53
Lead as Pb	1.5 µg/l	8
Fluoride as F	0.14 mg/l	8
Iron as Fe	7 µg/l	53

This selected example may not serve your postcode. Open the full report for ranges, source notes, any reported contraventions and the original document.

Read the full ABBEY WOOD report →

Find your local source-area report

Use the exact area name from the supplier’s checker. Older areas can have been renamed or replaced. Each card keeps the hardness period separate from other quality data.

Search by the exact source-area nameWith annual hardness history

245 areas match · showing 24.