⚗️ Sampling of drinking water from treatment works and the water supply network (PN-ISO 5667-5)

Physicochemistry PN-ISO 5667-5

Overview

SCOPE FROM THE PKN CATALOGUE CARD, QUOTED VERBATIM AND IN FULL (our translation): "This part of ISO 5667 gives guidance on techniques for sampling water intended for human consumption. For the purposes of this part of ISO 5667, water intended for human consumption includes: a) all water either in its original state or after treatment, intended for drinking, cooking, food preparation or other domestic purposes, regardless of its origin, and b) all water used in any food-production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption, unless the competent national authorities consider that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form. The guidance given in this part of ISO 5667 is restricted to situations where water comes from municipal distribution systems or similar systems (including individual systems) for which prior treatment and/or quality assessment has resulted in the water being classified as fit for drinking or for production purposes. This part of ISO 5667 applies in particular to water that is continuously supplied to each stage of use up to the point of use in the distribution system. This includes distribution in large buildings where additional water quality management may be applied. This part of ISO 5667 also applies to sampling where damage to distribution systems may occur, or in emergency situations in which the safety of the persons taking samples is not endangered. This part of ISO 5667 does not give guidance on water sources or on products made using drinking water. The following are examples of situations to which this document does not apply: sampling of water from its sources, such as groundwater and impounded surface water; sampling of drinking water from intermittent sources (for example from tankers); sampling from water tanks in aircraft, trains and ships; sampling of beverages (including bottled water) or of foodstuffs containing drinking water used in their preparation; sampling from drink dispensers which dispense open cups of drinks".

THE LIST OF EXCLUSIONS IS A LIST OF THE MOST COMMON MISTAKES. The last sentence of the scope lists five situations to which the standard does not apply — and each of them is in practice sometimes brought under "sampling of drinking water". Water from a tanker, bottled water, the water supply in a train and a drink from a dispenser are not cases for this standard, even though everywhere it is about water fit for drinking. The deciding factor is the method of supply: the standard concerns water supplied CONTINUOUSLY, by a distribution system.

STATUS AND CHOICE OF EDITION. The PKN card of the 2017-10 edition does not have the heading "Withdrawn". This edition implements ISO 5667-5:2006 [IDT] and replaces PN-ISO 5667-5:2003, which implemented the older ISO 5667-5:1991 and is withdrawn today. Citing the 2003 edition would therefore be citing a withdrawn document — the difference concerns not only the year, but also the international standard implemented. Publication date of the national edition: 24-09-2019, 24 pages, ICS 13.060.20 and 13.060.45.

SELECTION OF SAMPLING POINTS — SEVEN CRITERIA. The standard gives criteria for selecting the points: the points are to provide samples representative of the whole system or of its main parts; for each treatment works there is to be at least one point at the intake and at least one immediately after the outlet of the treated water; in systems with more than one source, the points are to reflect the yield of each source, the demand on it and the size of the population using it; the points are to be spread widely across the whole network, and their number proportional to the number of branches; among them there are to be points representative of the least favourable sources and points susceptible to contamination — loops, low-pressure zones and dead ends of the network; when waters from different sources mix in a complex system, the points are to make it possible to identify the contribution of each source; and where the network supplies large buildings (hotels, office buildings), points are to be both at the service connection and inside the building.

SAMPLING TAP — THIRTEEN REQUIREMENTS. The standard describes in detail what the tap intended for sampling should be like. The sampling line is to be as short as possible, in good condition and capable of being flushed at full flow; it must not protrude into the interior of the water pipe; it should connect to the pipeline just downstream of a valve, bend or fitting that causes turbulent flow; water from a branch of the network may not be regarded as representative of the water in the main pipeline; the material of the line is to be approved for contact with drinking water; the line must not contain tees in which water stagnates; the line and the tap are to be protected against frost; the point is to be protected against vandalism and contamination; if the tap is to be disinfected by flame, there must be no flammable materials or vapours nearby; there is to be enough space for filling bottles of various sizes; water is to be available at all times; the point is to have a drain so that the flushing water flows away freely; and for each permanent sampling point the sampler is to have a route map, a description of access and special instructions for flushing or sampling.

LOW FLOW AND DEPOSITS. The standard draws attention to sampling at very low flow: care must be taken not to disturb the deposit. If this cannot be avoided, a sufficient volume of water should be run off or one should wait until a steady state is established after the valve is opened.

PRACTICE OF A POLISH WATER UTILITY. The instruction of a water utility citing this standard together with PN-EN ISO 19458 gives for physicochemical testing: plastic bottles, removal of anti-splash devices (strainers), washing of the tap and setting the stream so that it does not splash, running the water for 3–5 minutes until the composition stabilises, rinsing the container with the water being sampled, filling with a continuous stream until it overflows — "to the brim", without air bubbles — and immediate closing and permanent labelling of the bottle.

WHAT WE DO NOT GIVE. We have a preview of the text of the standard covering the scope, the selection of sampling points and the requirements for taps; the further clauses (flushing of tanks and hydrants, on-site tests, frequency and times of sampling, sample volumes, sampling order, sampling for individual types of analysis) are in the inaccessible part. We therefore DO NOT GIVE: the flushing times required by the standard for tanks and hydrants, sample volumes, or the order of taking samples for different determinations.

Method principle

The sample is taken at a point chosen so that it represents the water in the system, not water standing in the service connection or in the fittings. Two operations follow from this: preparation of the point (removal of strainers, washing, disinfection if necessary) and flushing before sampling until the composition of the water stabilises. The sample for physicochemical testing is filled with a continuous stream until it overflows, without air bubbles, and closed immediately. For microbiological testing the rules of PN-EN ISO 19458 apply in addition, including sterilisation of the tap.

Applications

• Monitoring of the quality of water for human consumption in the water supply network — sampling from consumer taps and from control points
• Control of treatment works: sampling at the intake and immediately after the outlet of the treated water
• Networks supplied from multiple sources — identification of the contribution of individual sources at mixing points
• Large buildings (hotels, office buildings) — sampling at the service connection and inside the installation
• Investigation of failures and emergency situations in the distribution system
• Design of permanent sampling points: requirements for the sampling tap and its surroundings

Key parameters

Standard

Standard number

PN-ISO 5667-5:2017-10 (ISO 5667-5:2006)

Title (PL)

Jakość wody -- Pobieranie próbek -- Część 5: Wytyczne dotyczące pobierania próbek wody do picia ze stacji uzdatniania i z systemów dystrybucji

Title (EN)

Water quality — Sampling — Part 5: Guidance on sampling of drinking water from treatment works and piped distribution systems

Step-by-step procedure

1. Selection of the sampling point

   According to the criteria of the standard: representativeness for the system, intake and outlet of treated water, distribution in the network proportional to the number of branches, points susceptible to contamination.

2. Preparation of the point

   Remove anti-splash devices (strainers), wash the tap, set the stream so that it does not splash.

3. Flushing

   Run the water until the composition stabilises — in water utility practice 3–5 minutes. At low flow take care not to disturb the deposit; if unavoidable, run off a sufficient volume or wait for a steady state. WE DO NOT GIVE THE FLUSHING TIMES REQUIRED BY THE STANDARD FOR TANKS AND HYDRANTS.

4. Filling the container

   For physicochemical testing: rinse the container with the water being sampled, fill with a continuous stream until it overflows, "to the brim", without air bubbles.

5. Closing and labelling

   Close immediately and label permanently: point, date, time, type of water (raw, treated).

6. Transport

   Under refrigerated conditions, protected against damage, spillage, shocks and light; deliver to the laboratory on the day of sampling.

7. Sampling for microbiology

   Taps are sterilised if necessary in accordance with PN-EN ISO 19458 — the standard on sampling for microbiological testing, described separately in this database.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Sampling in emergency situations is carried out only when it does not endanger the safety of the sampler — stated explicitly in the scope of the standard
• Disinfecting the tap by flame requires that there are no flammable materials or vapours nearby
• Sampling from hydrants and in water chambers — work in confined spaces and in road traffic
• SUBSTANTIVE NOTE: water from a tanker, bottled water and drinks from dispensers are OUTSIDE the scope of this standard

Frequently asked questions