The Private Water Supplies (England) Regulations 2016

Regulation 12

SCHEDULE 3Sampling and analysis

PART 1General

Samples: general

1.—(1) A local authority must ensure that each sample is—

(a)taken by a competent person using suitable equipment,

(b)representative of the water at the sampling point at the time of sampling,

(c)not contaminated in the course of being taken,

(d)kept at such a temperature and in such condition as will secure that there is no material change in what is to be measured, and

(e)analysed without delay by a competent person using suitable equipment.

(2) It must ensure that the sample is analysed using a system of analytical quality control.

(3) The system must be subjected to checking by a person who is—

(a)not under the control of either the analyst or the local authority, and

(b)approved by the Secretary of State for that purpose.

Analysing samples

2.—(1) A local authority must ensure that each sample is analysed in accordance with this paragraph.

(2) For each parameter specified in the first column of Table 1 in Part 2 of this Schedule, the method of analysis is specified in the second column of that Table.

(3) For each parameter specified in the first column of Table 2 in Part 2 of this Schedule, the method is one that is capable of—

(a)measuring concentrations and values with the trueness and precision specified in the second and third columns of that Table, and

(b)detecting the parameter at the limit of detection specified in the fourth column of that Table.

(4) For hydrogen ion, the method of analysis must be capable of measuring a value with a trueness of 0.2 pH unit and a precision of 0.2 pH unit.

(5) The method of analysis used for odour and taste parameters must be capable of measuring values equal to the parametric value with a precision of 1 dilution number at 25°C.

(6) For these purposes—

“limit of detection” is —

“precision” (the random error) is twice the standard deviation (within a batch and between batches) of the spread of results about the mean;

“trueness” (the systematic error) is the difference between the mean value of the large number of repeated measurements and the true value.

Authorisation of alternative methods of analysis

3.—(1) The Secretary of State may authorise a method different from that set out in paragraph 2(2) if satisfied that it is at least as reliable.

(2) An authorisation may be time-limited and may be revoked at any time.

Sampling and analysis by persons other than local authorities

4.—(1) A local authority may enter into an arrangement for any person to take and analyse samples on its behalf.

(2) A local authority must not enter into an arrangement under sub-paragraph (1) unless—

(a)it is satisfied that the task will be carried out promptly by a person competent to perform it, and

(b)it has made arrangements that ensure that any breach of these Regulations is communicated to it immediately, and any other result is communicated to it within 28 days.

PART 2Analytical methods

PART 3Monitoring for indicative dose and analytical performance characteristics

Monitoring for compliance with the ID

5.—(1) A local authority may use various reliable screening strategies to indicate the presence of radioactivity in water intended for human consumption.

(2) These strategies may include screening for—

(a)certain radionuclides, or screening for an individual radionuclide;

(b)gross alpha activity or gross beta activity screening.

Screening for certain radionuclides, or screening for an individual radionuclide

6.—(1) If one of the activity concentrations exceeds 20% of the corresponding derived value or the tritium concentration exceeds its parametric value specified in the radioactive parameters table, an analysis of additional radionuclides is required.

(2) A local authority must take into account, in deciding which radionuclides are required to be measured for each supply, all relevant information about likely sources of radioactivity.

Screening strategies for gross alpha activity and gross beta activity

7.—(1) Subject to paragraph 6(1), the recommended screening values are—

(a)0.1 Bq/l for gross alpha activity, and

(b)1.0 Bq/l for gross beta activity(1).

(2) If the gross alpha activity exceeds 0.1 Bq/l or the gross beta activity exceeds 1.0 Bq/l, analysis for specific radionuclides is required.

(3) The Secretary of State may set alternative screening levels for gross alpha activity and gross beta activity where it is demonstrated by the local authority that the alternative levels are in compliance with an ID of 0,1 mSv.

(4) The determination by the local authority of which radionuclides to measure must be based on all relevant information about likely sources of radioactivity.

Calculation of the ID

8.—(1) The ID must be calculated from—

(a)the measured radionuclide concentrations and the dose coefficients laid down in Annex III, Table A of Directive 96/29/Euratom laying down basic safety standards for the protection of the health of workers and the general public against the dangers arising from ionising radiation(2), or

(b)more recent information recognised by the Secretary of State, on the basis of the annual intake of water (730 litres for adults).

(2) Where the following formula is satisfied, it can be assumed that the ID is less than the parametric value of 0,1mSv and no further investigation is required—

Performance characteristics and methods of analysis

9.  For the following parameters and radionuclides, the method of analysis used must, as a minimum, be capable of measuring activity concentrations with a limit of detection specified below—

Note 1: The limit of detection must be calculated according to the ISO standard 11929: Determination of the characteristic limits (decision threshold, detection limit, and limits of confidence interval) for measurements of ionising radiation – Fundamentals and application, with probabilities of errors of 1st and 2nd kind of 0,05 each(4).

Note 2: Measurement uncertainties must be calculated and reported as complete standard uncertainties, or as expanded uncertainties with an expansion factor of 1,96 according the ISO Guide for the Expression of Uncertainty in Measurement(5).

Note 3: The limit of detection for tritium and for radon is 10% of its parametric value of 100 Bq/1.

Note 4: The limit of detection for gross alpha activity and gross beta activities are 40% of the screening values of 0,1 and 1,0 Bq/1 respectively.

Note 5: This limit of detection applies only to initial screening for ID for a new water source; if initial checking indicates that it is not plausible that Ra-228 exceeds 20% of the derived concentration, the limit of detection may be increased to 0,08 Bq/1 for routine Ra-228 nuclide specific measurements, until a subsequent re-check is required.