DWI Information Letter 27/2000
24 November 2000
To: Board Level Contacts of Water and Sewerage Companies and Water Companies in England and Wales
Dear Sir or Madam:
WATER SUPPLY (WATER QUALITY) (AMENDMENT) REGULATIONS 1999 : CRYPTOSPORIDIUM IN WATER SUPPLIES : SAMPLING
Purpose
- The purpose of this letter is to provide a revision to the Standard Operating Protocol For The Monitoring of Cryptosporidium Oocysts In Treated Water Supplies To Satisfy Water Supply (Water Quality) (Amendment) Regulations 1999: Part 1 Sampling And Transportation of Samples (the Protocol).
Revision to Part 1 of the Protocol
- Part 1 of the Protocol has been revised in the light of recent experiences with the installation (and operation) of the sampling equipment. The revised version of the Protocol is enclosed with this letter. A list of the paragraph changes, with changes in bold, is included in Annex 1.
Enquiries
- Any enquiries about this letter should be sent to Brian Hoyle, Technical Assessor, 35 Burses Way, Hutton, Brentwood, Essex, CM13 2PL, tel: 01277 219492, or Mark Smith, Zone 2/A1, Ashdown House, 123 Victoria Street, London, SW1E 6DE, tel: 020 7944 5958.
- Copies of this letter are being sent to Pamela Taylor, Chief Executive, Water UK; Rodney Anderson, Water Supply and Regulation Division, Department of the Environment, Transport and 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 Ailsa Wight, Department of Health.
- Please acknowledge receipt of this letter using the enclosed slip and envelope.
Yours faithfully
Michael Rouse
Chief Inspector
Drinking Water Inspectorate
The following changes, in bold, have been made to Protocol 1:
- Para 2.1 - On Water Treatment Works Sites
- Para 2.1.1 - Contractors must be made aware of these obligations by the company and the potential risks involved in entering industrial (Water Treatment Works) premises for the purpose of sampling or maintenance. Company employees involved in sampling, maintenance or analysis must observe the company’s safety procedures.
- All of Para 2.2 - Sampling Equipment
- Para 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). If a tag is broken to facilitate repair or modification of the sample line or fittings then a white tag (see section 3.2.4 below) will be fitted after completion of the repair or modification and the numbers of the blue tag broken and the replacement white tag fitted shall be recorded in the relevant log book together with the reason for breaking the tag.
- Para 4.6 - It is recommended that no valves are fitted on the drain line from the sampling unit. The line should be installed such as to ensure the free flow of sampled water to a suitable drainage point. If installed in plastic material the drain line must be fitted such that it cannot be kinked. Care must be taken to ensure that the drain line cannot be blocked as this could lead to excessive build-up of pressure within the sample unit or prevent the taking of the required sample.
- Para 5.6 - The approved collection device and associated equipment must be housed in a DWI approved sampling cabinet fitted with an approved security padlock and an approved plastic security tag. The cabinet must be of suitable strength and designed to prevent ingress of water and to afford protection to the contents from the elements if the cabinet is located out-of-doors. The cabinet must be suitably vented with any ventilation panel secured in place by bolts (or studs) or chemical cement to prevent any unauthorised removal. A label identifying the location and giving a unique sample point reference must be securely fitted to the front of the cabinet. Where located out-of-doors the cabinet must be adequately protected. Such security must either be a fence protecting the treatment works or a purpose built fence around the sample location. Any out-of-door location must be adequately roofed over to afford protection whilst changing the filter or carrying out maintenance on the monitoring equipment. If required the sampling cabinet door may be fitted with a glazed panel to facilitate reading the instantaneous flow whilst the cabinet door is locked. Any such glazed panel must not be greater than 100mm * 500mm in size and must be rivetted and chemically cemented in place to make it tamper evident.
- Para 5.7 - The equipment within the sampling cabinet must comprise of the following items:
Upstream of collection device
i) pressure reducing valve set for an inlet pressure of 1.5 bar; if, see (iii) below, the pump is omitted from the specification then the pressure reducing valve must be set for an inlet pressure of 5.5 bar. On installations where the inlet pressure is consistently at or below 1.5 bar this pressure reducing valve may be omitted from the specification.
ii) to viii) are the same, then:
Downstream of collection device
ix) to xi) are the same, then:
xii) water meter - suitable for use at flow rates of up to 60 litres per hour (Kent PSM cold potable water meter PL10-115 or other meter designed for use at flows of 60 litres per hour and meeting BS5728 (ISO 4064) Class C specification). If required a water meter meeting the above specification but with the facility to provide a remote read-out may be fitted;
xiii) flow meter - suitable for measuring flows between 0.25 to 1.25 litres per minute range and fitted with switch to operate at low flow (0.5 litre per minute or less). The flow meter must have a visual readout within the sampling cabinet but may if required have the facility to supply a remote signal via telemetry;
- Para 5.8 - During the initial inspection all joints on the sampling line within the sampling cabinet upstream of the collection device (see items (i) to (vi) above) will be identified with a coating of a security paint or security tape by a DWI Inspector or DWI approved agent. If, after such coating is in place, it is necessary to break or tighten any joints or seals within the sampling cabinet upstream of the collection device, then the reason must be logged and the DWI contact shall be informed. A re-inspection will be arranged to allow the joints to be coated again with fresh security paint or security seals re-applied. If the water meter is changed, then the old meter identity number and that of the new meter fitted together with the readings on both meters must be logged and the information reported to the DWI contact.
- Para 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 may be incorporated into the PLC 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.
- Para 6.5
vi) Check that the inlet pressure displayed on the Control/Display cabinet is not in excess of 8 bar. If at the time of changing the collection device a high inlet pressure (greater than 8 bar) is indicated on the Control/Display cabinet without a corresponding high headloss (greater than 7 bar) the inlet pressure-reducing valve may be defective (see x) below).
viii) Remove the stored evidence bag related to the collection device in use from the inside of the door of the cabinet and record the headloss pressure reading, from the digital display on the control/display cabinet, on the evidence bag in the appropriate box.
Note: on the new design of evidence bag there are also boxes for recording of the inlet pressure and instantaneous flow (the recording of this information is optional).
x) Unlock the control/display cabinet and move the control switch on the panel to the off position.
Note: If the inlet pressure recorded at the end of the sampling run was greater than 8 bar and the headloss reading was less than 7 bar it is possible that the inlet pressure-reducing valve may be defective. In such cases it is recommended that after taking the inlet pressure and headloss pressure readings the pressure be relieved by breaking the blue DWI tag on the isolating valve outside the sampling cabinet and closing the valve. The control switch should then be switched to the "off" position before the sampling device is disconnected. If the pressure-reducing valve is suspected of being faulty the valve should be serviced and/or replaced as soon as possible. Once the company is satisfied that the pressure-reducing valve is functioning correctly the isolating valve should be opened and fitted with a white security tag (making a note of the blue tag number removed and the white tag number fitted in the logbook) and sampling recommenced. The matter should then be reported to the designated DWI contact so that a new DWI security tag may be fitted when appropriate.
xi) Note the reading on the water meter and enter the reading in the appropriate box on the evidence bag together with date and time. Check that the entered reading is not less than that recorded at the start of the sampling period (if necessary check water meter).
xii) Note the reading on the timer display on the control/display cabinet in the appropriate box on the evidence bag. Check that the entered reading is not less than that recorded at the start of the sampling period (if necessary check timer).
xiii) Disconnect the filter unit from the connecting hoses by means of the quick release connections. NB: there is no need to shut off the water supply as the filter unit holder is fitted with double shut-off valves and the inlet valve will be in the closed position after the control switch has been switched to the off position; however for safety reasons it is advisable to disconnect the inlet fitting prior to disconnection of the outlet fitting to ensure that there is no excessive build-up of pressure within the filter holder.
xvii) Take the replacement collection device and connect it to the hoses inside the cabinet, the quick fit connections are both key, and the outlet end colour coded, to ensure the flow direction will be correct. For safety reasons it is advisable to connect the outlet fitting prior to connection of the inlet fitting to ensure that there is no excessive build-up of pressure within the filter holder. The sampler must note the water meter reading and timer readings together with the time and date in the appropriate boxes alongside "Start of Run" on the new evidence bag and should check that these values agree (or are greater if maintenance work has entailed starting the unit) with those entered for finish of sampling run on the sealed bag containing the removed filter (if necessary re-check water meter and/or timer readings).
xix) Check that the water meter is registering the flow and the flow meter is reading 1 litre per minute and that the timer is operating. He/she must then note the differential ("headloss") pressure and record this in the appropriate box on the new evidence bag alongside "Start of Run".
Note: on the new design of evidence bag there are also boxes for recording of the inlet pressure and instantaneous flow (the recording of this information is optional).
NB: if the monitoring unit is under remote control and there is no flow from the works at the time then there will be no flow through the sampling unit. In this situation, where there is water in the main, readings may be obtained by turning the control switch to "local" for a few minutes; however if the main drains down under no flow conditions then no readings should be put in the relevant boxes and a comment "no flow from works at time of sampling" should be entered in comments box on the evidence bag.
xxi) Close and lock the cabinet and attach the appropriate plastic security tag (white) to the cabinet. The security tag must be fully tightened.
- Para 7.3 - Whenever the custody of the evidence bag is transferred on to another person, whether employed by the water company, or by a designated courier company, or by an approved laboratory, the transferee must ensure that the continuity section on the evidence bag is completed by the recipient at the time of the transfer.
- Para 7.4 - On delivery to the approved laboratory the person delivering must ensure that the continuity section on the evidence bag is completed by the recipient at the time of transfer. All records made on paper or the evidence bag must be in ink using a ball-point pen.
- Para 7.5 - A designated courier service, if using transport boxes, may have an electronic logging system in place to allow the journey of the transport container to be followed at all time, if this is the case, the requirement for paper receipts at all stages of the transportation of the samples can be waived. However, an electronic logging system does not obviate the requirement for completing the continuity section of the evidence bag at each transfer point during the transportation of the sample if it is not in a sealed tamper evident transport box.
| A - Z Index | Business and Technical | Consumer Information | Contacting us |
| DWI Home Page | News | Product Approval | Search our site | Wales |
Drinking Water Inspectorate,
Floor 2/A1, Ashdown House, 123 Victoria Street, London, SW1E 6DE
Telephone : 020 7944 5956 - Facsimile : 020 7944 5969
E-mail: dwi_enquiries@detr.gov.uk
Published 24 November 2000 Updated 11 July 2001
Return to Current Information Letters Index
Return to Information Letters Index
Return to Drinking Water Inspectorate Home Page
Department for Environment, Food & Rural Affairs (DEFRA)Home Page
The National Assembly for Wales / Cynulliad Cenedlaethol Cymru Home Page
Web site terms
© Crown copyright 2001