Rule clarifications
This table helps to clarify some of the interpretations in the Drinking Water Quality Assurance Rules.
The Drinking Water Quality Assurance Rules were published on 25 July 2022. When we next update the Rules, we will include any required amendments and clarify interpretations in the guidance we are developing.
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Rule / Requirement |
Rule / Requirement Description |
Rule / Requirement Clarification |
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T1.8 (page 26)
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Water leaving the treatment plant must be monitored for the determinands and at the frequencies set out in Table 10. |
The current stated compliance period in rule T1.8 and in Table 10 is 6 months. The actual compliance period is 3 months consistent with Rule G1 and Table 3. |
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Class 2 – Protozoa barrier – 3 log (page 36) |
Criteria: Groundwater sources that draw water from a depth of between 30 metres and 10 metres below ground level (with depth measured from ground level to the top of the upper most screen). |
Criteria clarification: Groundwater sources that:
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Class 3 - Protozoa Barrier – 4 log Criteria (page 37)
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Criteria: Groundwater sources that draw water from a depth of less than 10 metres below ground level (with depth measured from ground level to the top of the upper most screen), groundwater sources that draw water from a depth of 10 or more metres below ground level without a sanitary bore head, spring water sources and surface water sources. |
Criteria clarification: Groundwater sources that draw water from a depth of 10 metres or less below ground level (with depth measured from ground level to the top of the upper most screen), spring water sources and surface water sources.
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Requirement to meet a parameter for a percentage of a day when a treatment plant or process does not operate for all of a day |
Section 3.1 (page 14) states: Drinking water suppliers only need to demonstrate compliance against the Rules for periods when a drinking water supply is operating. Example: Rule T3.5 (page 41) Turbidity of water leaving the treatment plant must be less than 1 NTU for at least 95% of each day. |
Additional clarification for Section 3.1: A treatment plant or process “is operating” when it is producing drinking water to be distributed to consumers. Example: Rule T3.5 should be interpreted as: Turbidity of water leaving the treatment plant must be less than 1 NTU for at least 95% of the time the treatment plant is producing drinking water to be distributed to consumers. |
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UVT monitoring under T3 Bacterial Rules |
Section 4.10.1.4 Table 22 (page 46) requires UVT to be monitored for Water entering or leaving the UV reactor(s). |
The requirements of section 4.10.1.4 Table 22 are the same as the requirements of 4.10.2.13 Table 32 (footnote 56) (page 62): The requirement to monitor UVT does not apply to UV disinfection systems that automatically adjust the UV dose as the UVT of the water flowing through the reactor varies. The UV disinfection system may still require monitoring of UVT to meet the manufacturers’ validation criteria and requirements. |
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Membrane filtration process limitations under T3 Protozoa Rules |
Section 4.10.2.11 Table 29 (page 58) requires If flows of greater than 10% are recycled, separate treatment of the recycled stream is required to inactivate or kill protozoa and bacteria before the waste stream is returned to the plant upstream of the membranes. |
Inactivate or kill protozoa includes processes that remove protozoa. |
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Rule D3.26 and Table 35 (page 73) (D3 FAC sampling frequency)
Rule D3.29 and Table 39 (page 76) (D3 Microbiological Sampling Frequencies) |
Maximum interval between samples |
Maximum interval between samples (days) means a supplier must take the next sample before the maximum interval has elapsed. Example: If the supplier samples on Monday at 10 am and must meet a requirement for a 2-day maximum interval between samples, then another sample must be taken before the end of Wednesday. |
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Rule T2.1 and Table 14 (page 33) (T2 Treated Water Monitoring Requirements)
Rule D2.1 and Table 15 (page 35) (D2 Distribution System Monitoring Determinands)
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Duration between samples |
Duration between samples is the period that must elapse before a supplier can take the next sample. Example for Tables 14 and 15: If a supplier samples on Monday at 10 am and must meet a requirement for a ‘At least 2 Days’ duration between samples, another sample must be taken on Wednesday or thereafter. The supplier must still meet the sampling frequency requirement. These requirements should not be interpreted as limiting the amount of sampling done in a week. A supplier may take more samples than the sampling frequency, but at least two of those samples need to be taken with the specified duration between samples. |
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VP Rules for Supplies with Varying Population and Tables 41 and 42 (page 81) (VP Increased monitoring for requirements for treatment plants and distribution zones)
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Duration between samples |
Duration between samples means the duration must elapse before a supplier can take the next sample for compliance purposes. Example for tables 41 and 42: If a supplier takes a sample on Monday and the sampling frequency is daily with a duration between samples of 12 hours, they are required to take another sample on Tuesday. These requirements should not be interpreted as limiting the number of samples taken in a day. |
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T3 Chemical Rules - Chlorate Sampling |
Section 4.10.3 (page 64) states: If sodium hypochlorite is used, chlorate must be monitored weekly, regardless of the levels determined by sampling. |
Additional clarification for Section 4.10.3:
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