Information letters and advice notes

The Drinking Water Inspectorate uses Information letters and Advice notes to communicate with the water industry, local authorities and other relevant parties.

Information letters are used by DWI to communicate any changes in regulatory matters and Advice notes relate to changes in guidance or procedures.

They are automatically sent to named contacts but are available on request to anyone.

The list below includes only those letters that contain current information. Many older letters have been superseded. However, copies of such letters are available by contacting dwi.enquiries@defra.gov.uk

2024

REF	TITLE	Annex
03/2024 (Aug 2024)	INFORMATION LETTER Revised guidance specific to PFAS	Guidance on the Water Supply (Water Quality) Regulations 2016 (as amended) for England and Water Supply (Water Quality) Regulations 2018 for Wales specific to PFAS (per- and polyfluoroalkyl substances) in drinking water
R31-01/2024 (Aug 24)	INFORMATION LETTER Notification regarding Sika Combiflex 933	N/A
02/2024 (July 24)	INFORMATION LETTER The Water Industry (Suppliers’ Information) Direction 2024	Information Direction 2024 Annex A – File Specification Annex B – Information Direction 2024 Annex C – Parameter Code List Annex D – Portal User Guide
01/2024 (Revised) (Aug 24)	INFORMATION LETTER Annual Provision of Information on Consumer Contacts	Annex – Consumer Contacts
01/2024 (Feb 24)	ADVICE NOTE Revised guidance on regulation 8 of The Private Water Supplies (England) Regulations 2016, and The Private Water Supplies (Wales) Regulations 2017 (the Regulations)	N/A

2023

REF	TITLE	Annex
03/2023 (Aug 23)	INFORMATION LETTER The application of the Water Industry Act 1991, Water Supply (Water Quality) Regulations 2016 (as amended) to proposed new water recycling or desalination schemes	N/A
02/2023 (Mar 23)	INFORMATION LETTER PFAS – Inspectorate expectations for PFAS activity in AMP8	N/A
01/2023 (Feb 23)	INFORMATION LETTER The Water Industry (Supplier’s Information) Direction 2023	Information Direction 2023 Annex A – File Specification

2022

REF	TITLE	Annex
05b/2022 Revised (Dec 22)	INFORMATION LETTER Guidance for water companies in Wales with respect to drought orders	N/A
05a/2022 Revised (Dec 22)	INFORMATION LETTER Guidance for water companies in England with respect to drought orders	N/A
04/2022 Revised (Dec 22)	INFORMATION LETTER Annual Consumer Contacts	Annex A – Provision of information to the Drinking Water Inspectorate in respect of section 10 of the Water Industry (Suppliers’ Information) Direction 2021
03/2022 (Jul 22)	INFORMATION LETTER Information Letter 03/2022 is revoked	N/A
02/2022 (Mar 22)	INFORMATION LETTER Reporting of Taste Results	N/A
01/2022 (Mar 22)	INFORMATION LETTER Guidance on Alternative Supply Operations	Guidance on Alternative Supply Operations
01/2022 (Jan 22)	ADVICE NOTE  Notification of changes to transitional list of products/substances permitted for use in private water supplies	N/A

2021

REF	TITLE	Annex
05/2021 (Oct 21)	INFORMATION LETTER Information Letter 05/2021 is revoked	N/A
04/2021 (Sep 21)	INFORMATION LETTER Code of Practice on Technical Aspects of Fluoridation of Water Supplies 2021 (PDF 113KB)	Code of Practice on Technical Aspects of Fluoridation of Water Supplies 2021 (PDF 561KB)
03/2021 (Aug 21)	INFORMATION LETTER Radioactivity Notices (exemptions for monitoring) under the Water Supply (Water Quality) Regulations 2016 (as amended) (England) and the Water Supply (Water Quality) Regulation 2018 (Wales) (PDF 118KB)	Annex A – Conditions and Requirements for Radioactivity Exemption Applications (PDF 111KB)
02/2021 (Apr 21)	INFORMATION LETTER The Water Industry (Suppliers’ Information) Direction 2021 (PDF 113KB)	Information Direction 2021 (PDF 260KB) – supersedes the Water Industry (Suppliers’ Information) Direction 2020
01/2021 (Apr 21)	INFORMATION LETTER Reporting of Treatment Chemicals, Service Reservoir, Contact Tank and Final Water Storage Tank Information (PDF 53KB)	Annex A – Guidance and Specification (PDF 167KB) Service reservoirs, contact tanks and final water tanks template (XLS 19KB) Treatment chemicals template (XLS 19KB) updated 12/10/23

2020

REF	TITLE	Annex
07/2020 (Nov 20)	INFORMATION LETTER The Water Industry (Suppliers’ Information) Direction 2020 (PDF 80KB)	Information Direction (PDF 104KB)
06/2020 (Sept 20)	INFORMATION LETTER Assessment of the limitations for chemicals and treatment products intended for the treatment of drinking water (PDF 93KB)	N/A
05/2020 (July 20)	INFORMATION LETTER Chloramination disinfection and associated risks of cyanide formation in treated water (PDF 106KB)	N/A
04/2020 (May 20)	INFORMATION LETTER Information Letter 04/2020 is revoked	N/A
02/2020 (May 20)	ADVICE NOTE Maintaining drinking water quality when reinstating water supplies after temporary closure due to the CoViD-19 outbreak (PDF 97KB) Welsh version: At Aelodau Bwrdd a Chysylltiadau Bob Dydd Cwmnïau Dŵr a Charthffosiaeth a Chwmnïau Dŵr yng Nghymru a Lloegr (PDF 190KB)	N/A
01/2020 (Apr 20)	ADVICE NOTE Water suppliers’ responsibilities under Section 75(2) of the Water Industry Act 1991, the Water Supply (Water Fittings) Regulations 1999 and the Water Supply (Water Quality) Regulations 2016 (as amended) or the Water Supply (Water Quality) Regulations 2018 (Wales) (PDF 162KB)	N/A
03/2020 (Apr 20)	INFORMATION LETTER Information Letter 03/2020 is revoked	N/A
02/2020 (Mar 20)	INFORMATION LETTER Information Letter 02/2020 is revoked	N/A
01/2020 (Mar 20)	INFORMATION LETTER Information Letter 01/2020 is revoked	N/A

2019

REF	TITLE	Annex
03/2019 (Jun 19)	INFORMATION LETTER The Water Industry (Suppliers’ Information) Direction 2019 (PDF 248KB)	The Information Direction 2019 (PDF 92KB) Annex A (PDF 54KB) Updated GIS Specification Annex B (PDF 133KB) Revised file specification for compliance data returns Annex C (Excel 172KB) Updated Parameter list (updated March 2024)
02/2019 (Apr 19)	INFORMATION LETTER Reporting Requirements under Regulation 28 of the Water Supply (Water Quality) Regulations 2016 (as Amended) and the Water Supply (Water Quality) Regulations 2018 (Wales) (the Regulations) (PDF 74KB)	Annex A Guidance and Specification – Regulation 28 Reports (PDF 203KB)
01/2019 (Apr 19)	INFORMATION LETTER Drinking Water Quality Legislation (PDF 127KB)	N/A

2018

REF	TITLE	Annex
03/2018 (Dec 18)	INFORMATION LETTER METALDEHYDE – Recent developments and actions required (PDF 127KB)	N/A
02/2018 (Aug 18)	INFORMATION LETTER Monitoring Variations under Regulation 9 and Reporting Requirements under Regulation 28 of the Water Supply (Water Quality) Regulations 2016 (as Amended) and the Water Supply (Water Quality) Regulations 2018 (Wales) (the Regulations) (PDF 143KB)	Annex A – Guidance and Data Specification – Monitoring Variation Applications (PDF 173KB) (Version 2 updated Nov19) Annex B –  Guidance and Specification – Regulation 28 Reports Updated in annex A of IL 02/2019 (PDF 203KB)
01/2018 (Jul 18)	INFORMATION LETTER Drinking Water Quality Legislation (PDF 87KB)	N/A

2017

REF	TITLE	Annex
04/2017 (Dec 17)	INFORMATION LETTER Regulatory Sampling Programme (PDF 63KB)	N/A
03/2017 (Sept 17)	INFORMATION LETTER Update to guidance documents including a guidance note on long term planning for drinking water quality (PDF 119KB)	N/A
02/2017 (May 17)	INFORMATION LETTER Further guidance on Chromium in drinking water (PDF 122KB)	N/A

2016

REF	TITLE	Annex
04/2016 (Jun 16)	New drinking water quality legislation (2016) (PDF 152KB)	N/A
02/2016 (Mar 16)	Legislative changes relating to the DWI cost recovery scheme (PDF 61KB)	N/A

2015

REF	TITLE	Annex
02/2015	Legal Instruments – Processes for reporting on, agreeing changes to and closure/revocation (PDF 113KB)	1 – Undertaking progress (Word 45KB) 2 – Distribution consumer acceptability and discolouration schemes (Word 38KB) 3 – Notice progress (Word 41KB) 4 – Justification of proposed changes (Word 38KB) 5 – Undertakings completion report (Word 36KB) 6 – Notice completion report (Word 46KB)

2014

REF	TITLE	Annex
02/2014	Regulation 28 reporting requirements (PDF 110KB)	A – General requirements Updated in annex A of IL 02/2019 (PDF 203KB) B – Specification Updated in annex B of IL 02/2019 (PDF 203KB) C – Parameter/Hazard list (XLS 172KB) Updated March 2024 D – Example tables (Zip file 173KB) Updated September 2014 E – Query log (XLS 125KB) Updated 12 November 2014
01/2014	Metaldehyde and other pesticides (PDF 134KB)	N/A

2013

REF	TITLE	Annex
05/2013	Drinking water analysis and the regulatory requirements (PDF 95KB)	N/A
04/2013	Collection of data under the Private Water Supplies Regulations 2009 and the Private Water Supplies (Wales) Regulations 2010 (PDF 107KB)	1 – Return template (excel 438KB) Updated Oct 2020 Guidance on additional columns(pdf360KB) relating to radioactivity monitoring Updated Nov 2017 2 – Example return (excel 466KB) Updated October 2018 3 – Specification (PDF 202KB) Updated Oct 2020 FAQ (PDF 252KB)

2012

REF	TITLE	Annex
07/2012	Publication of further research on nitrosamines in water treatment coagulants and drinking water (PDF 102KB)	N/A
06/2012	Regulation 15 compliance arrangements (PDF 180KB)	N/A
02/2012	Arrangements for demonstrating that reporting of analytical results meet regulatory requirements (PDF 70KB)	N/A

2011

REF	TITLE	Annex
05/2011	Production, delivery, receipt and control of water treatment chemicals (PDF 101KB)	N/A
01/2011	Amendment to The Water Supply (Water Quality) Regulations 2010 (Wales) (PDF 92KB)	N/A

2010

REF	TITLE	Annex
10/2010	Guidance on using contractors to deliver Local Authority duties under the Private Water Supplies Regulations (PDF 113KB)	N/A

2009

REF	TITLE	Annex
4/2009	Submission of raw water monitoring data to the Drinking Water Inspectorate (PDF 138KB)

2007

REF	TITLE	Annex
08/2007	Guidance on interpretation of Regulation 16(2)(d)(i) of the Water Supply (Water Quality) Regulations 2000 (2001 in Wales) (PDF 87KB)	Guidance on implementation of Regulation 16(2)(d)(i) (PDF 130KB)

2005

REF	TITLE	Annex
12/2005	Guidance on sample and sample extract stability trials and the preservation and preparation of samples for metals analysis (PDF 135KB)	A – Guidance on sample and sample extract stability trials (PDF 169KB) B – Sample preservation and preparation for metals analysis of drinking water (PDF 102KB) C – Stability trial worked example (PDF 10KB)
03/2005	Guidance on the calibration and analytical quality control for residual chlorine measurements (PDF 76KB)	Guidance (PDF 169KB)

2004

REF	TITLE	Annex
11/2004	Information requirements following notification of an exceedence of a regulatory standard (PDF 80KB)	A – Pro forma (PDF 70KB)
05/2004	Commencement of Part 3 Provisions of Water Act 2003 (PDF 82KB)	N/A

2003

REF	TITLE	Annex
12/2003	Procedures for the Delivery of Water Treatment Chemicals (PDF 82KB)	N/A

2001

REF	TITLE	Annex
02/2001	Water Supply (Water Quality) Regulations 1989: Guidelines for Calibration in Laboratories (PDF 251KB)	N/A