Serving parts of North West London and the Home Counties.

Water Quality Information & Reports

We are committed to delivering high quality water, so we check water leaving our treatment works, at service reservoirs and at customers’ taps. This is part of our regulatory monitoring programme. The vast majority of the results comply with the standards set in the Water Supply (Water Quality) Regulations 2016, confirming that drinking water quality continues to be of a very high standard.

In 2018, we carried out over 180,000 tests on our water and our overall compliance performance was 99.96% while our Mean Zonal Compliance (MZC), the measure used by The Drinking Water Inspectorate (DWI), was 99.96%.


Water Quality information in your area

The Affinity Water area is split into 89 individual Water Supply Zones (WSZ). Each WSZ has its own Regulatory Compliance monitoring programme and reports are available for each of these Zones. These reports, also known as Schedule 4 reports, are produced annually for the previous year's programme and published in February of the following year. The reports detail the results of all the samples taken in that time period together with a comment if a sample failed to meet the required standard.

To see the report for the results of all samples taken in your WSZ, please enter your post code below.


This information is taken from historic results of monitoring and may be subject to change. This information is provided as a guide only and is subject to our terms and conditions.

Annual report on drinking water

Our annual report on drinking water quality details the 2018 water quality data for Affinity Water.

Within the report you will find details on our treatment processes, our water quality monitoring programme, the drinking water quality standards we must meet and the results for Affinity Water as a whole and our Undertakings to improve the quality of water leaving our treatment works and within our distribution network. It gives help with common water quality questions and has lots of useful information. Download Water Quality Report

For previous years’ reports please contact us.