What sampling is required?

The following gives guidance on what sampling is required by private supply type.

Sampling and monitoring for Regulation 8 supplies (private distribution systems)

The monitoring of each Regulation 8 supply must be based on the outcome of the regulatory risk assessment carried out for that supply. The relevant parameters and frequency of sampling should reflect the risk rating and the nature of the hazards identified in the risk assessment:

  • coliforms and E.coli (ingress into the network or poor hygienic conditions, especially tanks)
  • colony counts (upward trend may indicate deterioration of water quality)
  • conductivity, hydrogen ion and turbidity
  • iron and zinc (from corrosion of galvanised steel or cast iron pipes), manganese, aluminium
  • taste and odour (ingress and permeation of plastic pipes)
  • trihalomethanes and bromate (disinfection by-products) (especially if there is chlorination within the private distribution network)
  • lead, nickel and copper (from the pipe work or tap fittings in the private distribution network or within the premises

Sampling and monitoring for Regulation 9 supplies

There are two types of monitoring for Regulation 9 supplies (excluding supplies to tenanted dwellings in Wales, which fall within regulation 11 of The Regulations (Wales))

Monitoring of Group A parameters

The purpose of monitoring for Group A parameters is to:

  • determine whether or not water complies with the concentrations or values in Schedule 1 of the Regulations
  • provide information on the organoleptic (taste, odour and appearance) and microbiological quality of the water
  • establish the effectiveness of the treatment, including disinfection.

The parameters, ammonium, coliform bacteria, colony counts, colour, conductivity, E.coli, hydrogen ion concentration (pH value), odour, taste and turbidity, must be monitored in all large supplies at the check monitoring frequency.

Monitoring of Group B parameters

The purpose of monitoring Group B parameters is to:

  • determine whether or not the water complies with the concentrations or values in part 1 or 2 of Schedule 1 of the Regulations, other than Group A parameters already being sampled under part 1 of Schedule 2 (the standards and indicator parameters).
  • check (where disinfection is used), that disinfection by-products are kept as low as possible without compromising the disinfection.

See here for further information on likely sources of individual parameters. 

Criteria that could be used to decide on exclusion of a particular parameter from audit monitoring is given in the Information Note on Regulation 7 here.

Variation of monitoring requirements for Group A and group B parameters

A local authority may reduce the sampling frequencies required for a parameter, or cease to monitor a parameter (other than E.coli), but can only do so in accordance with the conditions specified in Part 2A of The Private Water Supplies (England) (Amendment) Regulations 2018 and Part 4 of Schedule 2 of The Private Water Supplies (Wales) Regulations 2017.

Sampling and Monitoring for Regulation 10 (England) Supplies and Regulation 11 (Wales) supplies

The Regulations require a local authority to monitor all its Regulation 10 supplies (except a supply to a single dwelling) at least every five years and more frequently if required by the risk assessment for the following parameters:

  • Conductivity
  • Enterococci
  • Escherichia coli (E.coli)
  • Hydrogen ion (pH value)
  • Turbidity
  • Any parameter in Schedule 1 to the Regulations identified in the risk assessment as being at risk of not complying with the concentrations or values
  • Any other parameter identified in the risk assessment as a risk to human health.

A local authority may monitor a private supply to a single dwelling for the same parameters listed above if it is concerned there may be a potential danger to human health. However a local authority can only charge for this service if requested by the dwelling owner or occupier.

Monitoring of radioactive substances

Regulation 11 (England) and Regulations 12 and 13 (Wales) of The Regulations requires that a local authority must monitor each private water supply in its area for radioactive substances. In England local authorities must ensure that this is carried out in accordance with the requirement of Part 3 of Schedule 3 of The Regulations (England), and in Wales Schedule 3 of the Regulations (Wales). Further information came be found in the Information Note for regulation 7 found here.

Further guidance on Group A and Group B parameters (England only)

The private water supplies regulations1 (the Regulations) in England require that all private water supplies that:

  1. Supply a volume of greater than 10m3 per day
  2. Are used as part of a public or commercial activity (regulation 9),

must be monitored according to both Group A and B monitoring specifications2, in addition to parameters that the risk assessment shows to be necessary.

The parameters listed in both groups must be monitored in accordance with the frequencies specified using the relevant tables in the Regulations (see below). The volume consumed is a key variable in ascertaining the frequency of monitoring.

How to determine which parameters must be monitored and at what frequency.

Group A parameter monitoring requirements:

Group A parameters should be selected for monitoring as follows.

From table 1, in Part 1 of Schedule 2 (headed “monitoring for Group A parameters”), select those parameters in column 1 that are pertinent to the circumstances shown in column 2. Some (those shown in green in the table below of these must be monitored on all supplies. Others are monitored only where specific circumstances are relevant.

Group A Parameters
Parameter nameCircumstance when the parameter must be monitored.
Aluminium IronWhere water is used as a water treatment chemical, or where the water originates from, or is influenced, by surface water
coliforms Colony counts 22oC colour conductivity E. coli Hydrogen ion Iron Odour Taste TurbidityIN ALL SUPPLIES
ManganeseWhere the water originates from, or is influenced from surface water
Ammonium Nitrate NitriteWhere Chloramination is practised

The frequency at which these parameters must be tested at each supply are derived from Table 2 of the same schedule (Part 1 of schedule 2). This is based on the volume of consumption of the supply being monitored:

Table 2

Same for this table

Group B parameter monitoring requirements

Group B parameters are listed in Schedule 1, Parts 1 and 2 of The Private Water Supplies (England) Regulations 2016.  These can be found in tables A, B and Part II of Part 1 and tables C and D in Part 2.

The frequency at which these parameters must be tested are shown in table 3 of the   Private Water Supplies (England) (Amendment) Regulations 2018 as follows.

Sampling arrangements

Where the testing frequency for both Group A and B parameters is once per year, the sample/s for each may be taken either in a single visit (via one or more separate samples) or on two separate visits at different times of the year. For the purposes of good practice, it is advised that Group A and B samples are taken at different times of the year.

For reporting purposes, it is important to remember that each individual parameter test must be either for a Group A parameter or a Group B parameter even if a single sample of water is tested for parameters in both groups.

Sometimes the same parameter may appear in both the Group A and the Group B specifications. If this is the case, that parameter does not need to be tested against the Group B specification, if it is already being tested against the Group A. specification.

  • One or more samples of water may be taken in a sampling visit.
  • Each of those samples may be tested for either Group A or Group B specifications, or a combination of both.
  • The number of samples is irrelevant. To comply with the regulations, each parameter must be tested at the correct frequency determined by the Group A and Group B specifications.
  • For reporting purposes, it is important to be clear on each sampling visit, which tests will be carried out on each sample, and against which specification, Group A or B.

Recording Group A and B parameter results in the data return

By 31 January of each year, every local authority in England and Wales must, send to the Inspectorate a data return for the private water supplies in its area, as part of its regulatory obligations. A specification guidance document is provided on the Inspectorate’s website to assist with the completion of this. This can be found here

Each parameter that was monitored throughout the year for each regulation 9 supply must be listed row by row, in the data tab, giving the purpose/reason why it was monitored on that day, in column F.

This reason must be selected from a dropdown list provided (copied below). If the parameter was tested for Group A reasons, “GPA” should be selected, and “GPB” where it was taken for Group B reasons.

  • GPA (Group A)
  • GPB (Group B)
  • Reg8 (parameters sampled from Reg 8 supplies)
  • Reg10 (parameters sampled from Reg 10 supplies)
  • Reg11 (parameters sampled from Reg 11 supplies – Wales only)
  • ARA (additional parameters arising from the risk assessment)
  • INV (Investigation)

Back to top