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Information Letters

Drinking Water Inspectorate: Information Letter 2/2000 - 21 January 2000

To: Board Level contacts of Water and Sewerage Companies and Water Companies in England and Wales

Dear Sir/Madam,

Water Supply (Water Quality) (Amendment) Regulations 1999 : Cryptosporidium in Water Supplies: Sampling

Purpose

1. The purpose of this letter is to advise:

Approved suppliers of control/display and sampling cabinets

2. DWI Information Letter 10/99 provided details of one approved supplier of control/display and sampling cabinets. The Inspectorate has now approved a further supplier of these cabinets. The two suppliers are Hydraulic Modelling Services Limited and Watercare Sampling Systems Limited and full details are given at Annex 1.

Revision to part 1 of the protocol

3. Part 1 of the protocol has been revised in the light of recent experiences with the installation (and operation) of the sampling equipment. The revision also includes corrections of some typographical errors and details of the new approved supplier of control/display and sampling cabinets. The revised version of the protocol is available at the end of this document. A list of the changes, highlighted in bold, is given at Annex 2.

Further guidance on the installation of approved sampling equipment

4. Following requests for further guidance on the installation of approved sampling equipment, a document has been prepared by one of the Inspectorate's contractor (Brian Hoyle). A copy of this document entitled "Monitoring Equipment for the Continuous Sampling of Cryptosporidium in Treated Drinking Water" (is available here in Adobe Acrobat format for download).

Research report on the sampling trials

5. A copy of the report entitled "Continuous Sampling for Cryptosporidium in Water Supplies" prepared by Brian Hoyle can be obtained from address at the end of this document. This report gives details of the trials undertaken on behalf of the Inspectorate. The results of these trials assisted in the preparation of the Water Supply (Water Quality) (Amendment) Regulations 1999 and the accompanying protocol.

Enquiries

6. Any enquiries about this letter should be sent to Mark Smith, Zone 2/A1, telephone 020 7944 5958.

7. Copies of this letter and the attachments are being sent to Pamela Taylor, Chief Executive, Water UK; Bob Dinwiddy, Water Supply and Regulation Division, Department of the Environment, Transport and the Regions; Bob Macey, Environment Division, The National Assembly for Wales; Tim Hooton, Water Services Unit, Scottish Executive; Randal Scott, Drinking Water Inspectorate for Northern Ireland; Rowena Tye, Office of Water Services and David Harper, Department of Health.

8. Please acknowledge receipt of this letter using the attached slip and reply paid envelope.

Yours faithfully

Michael Rouse

Chief Inspector

Annex 1

Approved suppliers of control/display and sampling cabinets

Hydraulic Modelling Services Limited
Reagent House
35 Colville Road
South Acton Industrial Estate
Acton
London W3 8BL

Contact Mr Peter Jackson (Managing Director)
Telephone 0181 993 6621
Facsimile 0181 993 6621

Watercare Sampling Limited
Bittadon
Barnstable
Devon
EX31 4HJ

Contact Mr Richard Jerrard (Managing Director)
Telephone 01271 850588
Facsimile 01271 850516

Annex 2

List of amendments to Part 1

1.4 The conditions of sampling and examination must be such as to permit the use of the analytical results as evidence in a Court of Law. The Standard Operating Protocol therefore describes a system that would ensure both the scientific quality of the results, and a chain of evidence maintained in compliance with the Police & Criminal Evidence Act 1984. The protocol covers the minimum requirements to satisfy this requirement.

3.2.2 Security tags used on the sampling line and fittings will be made of plastic, blue in colour and each with a unique number. These security tags will be controlled and fitted only by DWI Inspectors or DWI approved agent(s).

3.2.5 Security tags used by DWI Inspectors or a DWI approved agent to reseal equipment after auditing will be made of plastic, blue in colour, each with a unique number. These security tags will be controlled and fitted only by DWI Inspectors or DWI approved agent(s).

3.3.1 Padlocks used on the control/display cabinet and sampling cabinet must be of DWI approved design (Abloy PL221/50 with two working keys provided for the two padlocks). Each set of padlocks must have a unique identification number stamped or engraved on the body of the locks and keys, and include a suffix "a" or "b" to differentiate the two keys used for each set of padlocks. The working keys will be common to both locks. A set of master keys shall be held by DWI or DWI designated agents to facilitate unannounced audits; the working keys must be held by the water company at secure locations.

4.2 The sampling line should preferably be of 15 mm copper (or other DWI approved material). The sampling line must be of as short a length as is practicable. The sampling line must be fitted with a stop valve as close to the point of connection to the main as is practicable, and must also terminate in a stop valve with a G1/2 (1/2 inch BSP) fitting appropriate for connection to the sampling cabinet on the outlet side. The stop valves must be fitted with suitable lugs (attached by a brazed weld) to allow the attachment of plastic security tags (see section 3.2.2). Any other fitting on this sampling line must also incorporate suitable lugs to allow the fitting of security tags, however no fitting or equipment shall be incorporated in the sampling line without permission in writing from the DWI for that particular sampling line.

4.5 A suitable 110 or 220 volt electrical supply point must be available within 0.5 metre of the control/display cabinet. This point should be of a waterproof design. If an isolator switch is fitted at this point it is recommended that this should be housed within a break-glass box or other covered container that can have a security seal attached and suitably labelled to ensure that it is not switched off accidentally.

5.1 The approved sampling equipment must be housed in two units henceforth termed the control/display cabinet and the sampling cabinet which have a IP65 rating. The water company must wherever possible provide facilities for connection of the monitoring equipment alarms and pressure readouts via telemetry lines to their electronic pick up system. On treatment works where insufficient telemetry capacity is available, it is suggested that a local data logging facility may be provided to capture the alarms and readings. On treatment works which are not manned for 24-hours per day and which supply water whilst unmanned a minimum of one telemetry line must be available to transmit a general alarm to the control centre when any alarm signal on the monitoring equipment is activated. A push-button test facility shall be fitted to the front of thecontrol/display panel to enable all alarm lights to be checked.

5.3 The control/display unit must be controlled by a Programmable Logic Controller (PLC) or other suitable microprocessor control system and must have displays reading the inlet pressure and headloss across the approved collection device used to take the sample. The control/display cabinet must be fitted with an electronic timer (non-resetable) with display reading in hours to two decimal places and up to 999999.99 hours with roll over zero. The timer shall be controlled so that it is running when the sample pump is operating except where no pump is fitted because the inlet pressure is always in excess of 5.5 bars when the timer shall be controlled so that it is running when the inlet solenoid valve is open. The control/display cabinet must have a control switch to allow local or remote operation or isolation of the monitoring equipment. Displays for inlet pressure, headloss and timer shall be clearly visible at all times even when the unit is located in a dark environment, and the size of the displays for each reading shall be to a minimum of 1/8 DIN.

5.5 The control/display cabinet must be supplied with power from a suitable external source.Where a backup power supply is available for continuity of supply in the event of a mains failure, the control/display cabinet must also be supplied with a backup power supply. In the event of total power failure the control/display unit must be capable of sending an alarm via the telemetry system to a control room to indicate power failure.

5.7 The equipment within the sampling cabinet must comprise of the following items:

5.10 At treatment works where the supply is intermittent, and the main is not kept fully charged when the supply is off, a delay must be incorporated into the system to ensure that sampling does not commence until the main is charged. This delay is to ensure that introduction of air into the sampling unit is minimised. The delay between receiving a signal and opening of the inlet solenoid valve must not exceed 5 minutes unless so authorised by a DWI Inspector or DWI approved agent(s) in writing. All delay times programmed into the control system shall be noted on a label affixed within the control/display cabinet.

The Annexes are available in Adobe Acrobat format for download. The Adobe Acrobat Reader can be freely downloaded.

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Drinking Water Inspectorate,
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Telephone : 020 7944 5956 - Facsimile : 020 7944 5969
E-mail: dwi_enquiries@detr.gov.uk

Updated 21 July 2000 Updated 11 July 2001
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