Sampling and monitoring

Regulation 7 (England) (Wales) requires that each local authority monitors (sample and analyse) all the private water supplies in its area for the required parameters, in accordance with Part 2 of the Regulations to fulfil its duties under Section 77(1) of the 1991 Act.

Schedule 3 of The Private Water Supplies Regulations 2016 (2010 in Wales) also requires that local authorities must ensure that each sample it takes is:

  • taken by a competent person;
  • representative of the water at the sampling point at the time of sampling;
  • not contaminated in the course of being taken, stored or transported.

To aid local authorities in conducting this duty the Inspectorate has produced a sampling manual which outlines all the required information to ensure regulatory monitoring requirements are met by way of standard best practice.

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:

Check monitoring

Undertaken relatively frequently for a few very important parameters, the purpose of check monitoring 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.

Audit monitoring

Undertaken less frequently for the remaining parameters. Local authorities can omit parameters from ‘audit monitoring’ for particular supplies if they can demonstrate by risk assessment and results of previous monitoring that those parameters are unlikely to be present or present at concentrations well below the standards.

The purpose of audit monitoring (for any parameter not included in check monitoring) is to:

  • determine whether or not the water complies with the concentrations or values in Schedule 1 of the Regulations (the standards and indicator parameters)
  • check if disinfection is used, that disinfection by-products are kept as low as possible without compromising the disinfection

The Likely sources of individual parameters table (PDF 26KB) provides information on likely sources of specific parameters within a private water supply.  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 (England) (Wales).

Sampling and Monitoring for Regulation 10 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.


Page reviewed: 15 September 2016
Page modified: 15 September 2016

Drinking Water Inspectorate