AS 5667.5:2022 – Water quality -Sampling Part 5: Guidance on sampling of drinking water from treatment works and piped distribution systems (ISo 5667-5:2006,MOD).
3 Design of sampling programmes
Before the first paragraph, add the following:
Sampling protocols wtll differ, depending on the desired objective and it is the role of the Sampling Programme to clearly identify the desired outcomes of the sampling. The Sampling Programme, as a minimum, should include directions of the sampling method to be used and what the outcome of the sample results will mean (i.e. Identification of appropriate guideline values or operational targets for each parameter).
The following sampling factors should be addressed in the Sampling Programme:
(a) Identification of the water to be characterized. For example, if the sample is designed to represent distributed water, as It is delivered to the tap or a consumer point (see AS 2031— 2012) or other.
(b) The type of sampling method to be used. One or multiple sampling methods may be found appropriate to best represent the objectives of the Sampling Programme. For example, random daytime (RDT) sampling or stagnation sampling method may he required to complement traditional distribution sampling methods.
(c Whcthersample point disinfection Is required. and lfso by what method (see AS 2031—2012).
(d) The duration of sample tap flushing may vary based on the local conditions of the sample tap. For example, the programme maybe targeting first draw, or a fixed draw volume to determine water quality in a specific location in the water distribution network such as a thermostatic mixing valve.
(e) The volume of sample to be collected (e.g. 1 L or 2 L may be found more appropriate to better represent the average metal content compared to a 60 mL sample).
(f) Consideration of the material of the sample tap to ensure it does not affect the parameters being tested for. For example, copper sample tap outlets may not be appropriate if the Sampling Programme Is targeting variations In copper concentration In the distributed water network. See Clause 5.5.2 for more information on sampling taps.
(g) Whether tap attachments should be removed or left in place during sampling.
The guidance given in this document is generic in nature, and specific sampling procedures for certain parameters and situations may require alternate and specific methods. For example, alterations to standard methods may be required for sampling for parameters such as per- and polyfluoroalkyl substances (PFAS).
For further guidance, refer to Australian Drinking Water Guidelines, Chapter 9 and Health Canada’s Lead in Drinking Water.
Programmes for the sampling of drinking water, including statistical considerations, should be designed in accordance with ISO 5667-1.
Microbiological investigations of drinking water should be designed and implemented in accordance with ISO 19458.
Samples should be collected from the inlet and outlet pipes as close as possible to the service reservoir. The outlet sample location should be upstream of the first customer.
If a service reservoir has a common Inlet and outlet main, samples should, where possible, be collected when the main is acting as an outlet and the water quality is therefore representative of water that has been stored in the service reservoir. If this cannot be achieved, a sample collection pumping system should be installed and utilized.
If a service reservoir has more than one compartment hut the compartments are hydraulically connected, the compartments may be regarded as a single reservoir. If a service reservoir has more than one compartment and these compartments are not hydraulically connected, each compartment should he considered as a separate service reservoir and should be assigned individual sampling points, except ii the individual outlets from the compartments combine into a common outlet, in which case a single sample location on the common outlet might be adequate.
Sometimes (for example, when a reservoir has been out of service or cleaned, when there is no sampling valve on the outlet pipe, or when the surface layer of the reservoir is to be analysed), it might be necessary to take dip samples, as described In 6.5 from the service reservoirs, although this means of sampling should be avoided wherever possible. If it is essential to take dip samples, special care should be taken to ensure that the sampling operation does not introduce debris into the water and that equipment is sterilized before sampling to avoid a microbiological compromise of the water in the reservoir.
5.3 Water treatment plants
Samples should he collected from the inlet and outlet pipes as close as possible to the treatment plant. For monitoring of the different stages (for example, sedimentation and filtration) of water treatment, sampling should take place before and after the respective stage being monitored. If there is disinfection and/or an oxidation plant, sampling should be carried out as described in 5.4.