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Regulation 7 (Monitoring)
Regulation 7 details the required frequency to collect samples for water quality analysis to comply with the regulations.
Monitoring provides crucial information to determine the status of a supply at a moment in time – the time the sample was taken. Monitoring is used to identify supplies that do not meet water quality standards and for the evaluation or verification of control measures introduced to supply systems to ensure compliance.
Local authorities must monitor all private water supplies according to their supply type (regulation 8, 9 or 10). Monitoring for regulation 8 and 10 is relatively straightforward, but regulation 9 monitoring is more complex and forms most of the appendices to this note. Samples from private water supplies should be collected from a point where the water is consumed. In most cases this will be at a kitchen tap, but it may vary, for example at a premise where the water is being used to manufacture a food product.
The sampling requirements of a private water supply must not be determined solely by the usage of the building from where the sample is being collected. (i.e. whether it is in commercial or domestic use). If the water on one or more buildings on the supply are being used as part of a commercial or public activity, then the entire supply must be monitored in accordance with regulation 9. Regulatory samples should not be collected from multiple buildings on each sampling visit, but only from a single point of use at a suitable location on the supply. This is the case unless there is no single point of treatment (e.g. multiple buildings, each with their own individual treatment devices). Annex 1 details the issues to consider when determining the suitability of sampling locations.
The requirements for the monitoring of The Private Water Supplies Regulations 2016 (as amended) are found in schedule 2 of the amended Regulations and are explained further in Appendix 2 and 3 below.
Sampling, storage and transportation of samples must be undertaken in accordance with a sampling scheme, the basis of which is a standard sampling manual. This requires that samplers are certified by companies that are accredited to deliver this scheme under ISO 17024. A list of organisations participating in the scheme is available at www.dwi.gov.uk
If the sampling procedures of a local authority or a contracted sampling service provider are already accredited to the ISO 17025 standard, then it does not require its samplers to be certified in accordance with the ISO 17024 sampling scheme.
In general, where there are two or more properties on a supply, sampling and other costs should be shared amongst appropriate relevant persons in a fair and proportionate manner, as the local authority sees fit. How this is done will vary and should be determined on a case by case basis. It is however necessary when selecting a suitable sampling point that it best represents the water being consumed on the supply.
Regulation 8 supplies
The selection of parameters for the frequency for monitoring of regulation 8 supplies is determined by the risk assessment findings – see information note on regulation 8.
Regulation 9 supplies
Local authorities must carry out Group A monitoring and Group B monitoring and any additional monitoring that the risk assessment shows to be necessary. See information note on regulation 9 in addition to Appendix 2 below.
Group A and Group B monitoring at specified frequencies, depends on the volume of water being consumed for domestic purposes. Where this volume is unknown, the local authority should estimate the volume by multiplying the number of people supplied by an assumed water consumption of 0.2m3/day (200 litres/day). See Appendix 2 table 4.
The details of group A and Group B monitoring for regulation 9 supplies are set out in Appendix 2 in tables 1, 2, 3 and 4. Table 5 provides an overview of likely sources of all the listed parameters and should be considered with the regulation 6 risk assessment when determining the monitoring programme.
Regulation 10 supplies
All regulation 10 supplies except for regulation 10(3) supplies (so called single dwellings) require monitoring for five specified parameters once every five years: conductivity; Enterococci; E.coli; pH; and turbidity. They are not subject to Group A and B monitoring.
A local authority must increase the frequency of monitoring if the risk assessment shows this to be necessary. Additional parameters may be monitored where a risk assessment has determined a risk of not complying with any other PCV or where there is a potential danger to human health.
Supplies to single dwellings do not require monitoring unless it is requested by the owner or occupier of the dwelling. Where a local authority suspects a risk to health then it should investigate in accordance with regulation 16, and it is recommended that sampling is undertaken as part of the investigation.
Special circumstances for monitoring
The monitoring requirements for water fountains and supplies used only for toilet flushing are detailed at Appendix 3.
Annex 1 Suitability of sampling locations
Samples must be taken in a way that ensures (a) the sample is representative of the water being consumed on that supply (b) the monitoring fees and other charges are applied in a fair and proportionate manner, particularly where there are 2 or more buildings on the supply and/or more than 1 relevant person exists.
It is not a specified regulatory requirement to collect a regulatory sample at each property on the supply, although more than one sample may be collected using a risk-based approach and/or as part of a regulation 16 investigation. It is only necessary to collect the regulatory sample from a single point of use at a suitable location on the supply, where the quality of the water consumed is best represented.
The sampling location must ensure that the sample best represents any hazard identified on the risk assessment. In some cases, where there are multiple buildings or rooms on a private supply it may be appropriate to alternate between them to assess the water quality across the whole supply over time. Other considerations when determining a suitable sampling location include:
- The number of relevant persons associated with the supply.
- The configuration of the distribution system, the plumbing metals present and the suitability of tap types at the various premises.
- The suitability of sampling locations and the hygienic conditions of the immediate surroundings.
- Whether or not there is an overall supply owner who as a relevant person accepts responsibility for the provision and quality of the overall supply.
- Any local (legal or customary) agreements relating to the responsibility for the supply and its upkeep where there are multiple users/relevant persons.
- Any potential breaches of regulation 5 (substances and products), within buildings, which may influence the sample results (i.e. water fittings and product materials). These should be remedied through the risk assessment process, using enforcement where relevant.
- Any potential risks of non-compliance with regulatory standards due to inadequate building specific treatment arrangements (for example, poorly maintained UV treatment).
- Inadequate distribution system (for example, lead pipes) between buildings. These should be remedied through the risk assessment process, using enforcement where relevant.
Appendix 2 Group A and B monitoring of regulation 9 supplies:
The purpose of Group A monitoring is to establish levels of specified microbiological, chemical and organoleptic parameters for determining compliance with drinking water quality standards and the effectiveness of existing control measures and those introduced following risk assessment are working satisfactorily.
The specified Group A monitoring parameters are shown in table 1, Some parameters are mandatory, whereas others need only to be monitored if the circumstances specified in the table 5 exist.
Table 1: Monitoring for Group A parameters
When used as flocculant or where the water originates from, or is influenced by, surface waters
Where the water originates from, or is influenced by, surface waters
In all supplies
Escherichia coli (E.coli)
Hydrogen ion concentration
When chloramination is practised**
Only in the case of water in bottles or
** The Regulations do not require residual chlorine disinfectant to be monitored but it is strongly recommended that local authorities monitor this at the Group A monitoring frequency.
*** Where the water is offered for free. If it is for sale, then it will be covered by the Natural Mineral Water, Spring Water and Bottled Drinking Water (England) Regulations 2017’.
Table 2: Sampling Frequency for Group A Parameters
> 5,000 ≤ 6,000
10 ≤ 100
> 6,000 ≤ 7,000
100 ≤ 1,000
> 7,000 ≤ 8,000
1,000 ≤ 2,000
> 8,000 ≤ 9,000
2,000 ≤ 3,000
> 9,000 ≤ 10,000
3,000 ≤ 4,000
37 [4 + (3 x 11)]
4,000 ≤ 5,000
40 [4 + (3 x 12)]
*For volumes greater than 10,000 the formula 4 + (3 x n) is used to calculate Group A monitoring frequency:
4 + (3 x n)
Where n = the number of 1,000m3/day rounded up to the nearest multiple of 1,000m3/day.
Part 2A of the Private Water Supplies (England) (amendment) Regulations 2018 allows a local authority to reduce the frequency of Group A and B monitoring for all parameters except Escherichia coli, provided that:
(a) The results from samples taken in respect of that parameter collected at regular intervals over the preceding three years area all at less than 60% of the PCV;
(b) The results of a risk assessment described in regulation 6(l) are considered, and that risk assessment indicates that no factor can be reasonably anticipated to be likely to cause deterioration of the quality of the water;
(c) Data collected during discharging its monitoring obligations are considered.
For any parameter collected at regular intervals over the preceding three years, if results are less than 30% of the PCV then the local authority may cease to monitor any parameter other than E.coli provided that—
(a) The results of a risk assessment described in regulation 6(l) are considered, and that risk assessment indicates that no factor can be reasonably anticipated to be likely to cause deterioration of the quality of the water;
(b) Data collected during discharging its monitoring obligations under this part are considered.
A local authority may set a higher frequency for any parameter if it considers it appropriate, considering the findings of any risk assessment.
Each local authority is required to carry out a risk assessment of each private water supply. A local authority may increase the frequency of monitoring for a parameter if it considers it appropriate from the results of the risk assessment, for example, because the risk assessment shows that the concentration or value of the parameter is likely to vary considerably. A local authority may include any other parameter or any other substance if it considers it appropriate from the results of the risk assessment. For example, arsenic may be included in the monitoring suite if the natural geology indicates that it may be present.
There are certain parameters which are controlled using approved products under regulation 5, and for which monitoring is therefore not informative. Where products containing these parameters are not part of the supply system, then there is no need to monitor for these parameters. Unapproved products identified in the supply system during risk assessment may require monitoring for parameters otherwise controlled through regulation 5 and the product approval process – see regulation 5 information note.
Group B monitoring frequency
Table 3: Group B monitoring frequencies
10 – ≤ 3,300
3,300 – ≤ 6,600
6,600 – ≤ 10,000
5 [3 + (1 x 2)
6 [3 + (1 x 3)]
10,000 – ≤ 100,000*
3 + 1 for each 10,000 m3/day of the total volume (rounding up to the nearest multiple of 10,000 m3/day)
15 [10 + (1 x 5)]
10 + 1 for each 25,000 m3/day of the total volume (rounding up to the nearest multiple of 25,000m3/day)
* For volumes greater than 10,000 the formula 3 + (1 x n) is used to calculate Group B monitoring frequency:
3 + (1 x n)
Where n = the number of 10,000m3/day rounded up to the nearest multiple of 10,000m3/day.
** For volumes greater than 100,000 the formula 10 + (1 x n) is used to calculate Group B monitoring frequency:
10 + (1 x n)
Where n = the number of 25,000m3/day rounded up to the nearest multiple of 25,000m3/day.
Inclusion of additional parameters
For each type of supply the Regulations permit the monitoring of any parameter, whether listed in the Regulations or not where a local authority considers it appropriate from the results of the risk assessment. For example, it could include silver, if silver or silver compounds are incorporated in any filtration system used to treat private water supplies (the World Health Organisation (WHO) guidelines suggest that silver levels up to 0.1mg/l can be tolerated without risk to human health) or zinc if galvanised pipework has been used in distribution or domestic plumbing (the WHO guidelines suggest that zinc levels over 3.0mg/l may be regarded as unacceptable by consumers). Likewise, chloride may indicate some types of groundwater contamination (saline intrusion).
Where Cryptosporidium is deemed a risk as identified by the risk assessment, the presence or absence of oocysts on any sampling occasion will not be informative. Therefore, the only time that testing is relevant is an outbreak or when confirmed cases of cryptosporidiosis are being investigated.
Unacceptable taste and odours often arise because the drinking water source itself may have become contaminated following historical industrial contamination, or there has been a fuel, heating oil or solvent spill affecting the supply system.
Hydrocarbon-related ground contamination is particularly problematic where plastic pipes have been laid, since these chemicals can migrate through the plastic water pipes and contaminate the supply. Where this has occurred, the solution is normally to replace the contaminated pipes with barrier piping.
Fuels and solvents are complex mixtures of chemicals with extremely low taste and odour thresholds meaning that they are detectable in the water at concentrations well below those of concern for health, hence it is not appropriate to set a healthbased standard. Because of this, if a fuel taste or odour is detected it is not necessary to undertake extensive testing and analysis for exotic organic compounds – the water will be unwholesome by the taste and odour present in it.
Detection of indicator parameters above the specification or value require an investigation to determine the cause. The appropriate action is determined by the cause. For some parameters which are found to be naturally occurring, Public Health England can advise whether it is safe to use at the concentration found. If the cause is contamination the source of the contamination should be determined and mitigated.
Where a sample exceeds a standard for a parameter(s), the local authority must carry out an investigation under regulation 16. Additional repeat testing will be required to help determine the cause and extent of the failure, as part of the investigation (i.e. a risk-based site inspection). Local authorities should not rely on repeat sampling alone to determine whether a supply is wholesome and/or a potential danger to health or not. Local authorities are not permitted to charge for any sample taken and analysed solely to confirm or clarify the results of the analysis of a previous sample.
Once the cause has been established the local authority must serve a notice in accordance with regulation 16 or 18, as required to mitigate the risks identified by the investigation.
When a parametric value for a radioactive substance is exceeded it must be investigated as follows:
a) Review the results of other private supplies from the supplying aquifer (including any information from the incumbent water undertaker if they abstract from the same aquifer) as to whether this is unusual for the aquifer.
b) If the results for the sample provided are shown to be similar to the aquifer, then providing previous investigations into indicative dose value has been found not to exceed 0.1mSv/year then no further investigation will be required unless there is an upward trend in the value of the failing parameter.
c) If the indicative dose exceeds 0.1 mSv/year an investigation into the cause should be undertaken. If the supply has not exceeded the PCV before, then an investigation into cause and indicative dose levels will be required. Resamples should be taken from the original private water supply as well as from other private supplies from the same aquifer. The risk assessment should be updated with any changes within the local area, for example: if this is a new supply, if there is a local historical environmental cause, etc. If the resamples confirm the levels of the initial result, then indicative dose assessment will be required.
d) Arrangements should be made with a suitably qualified laboratory to carry out analysis and calculation of indicative dose. If the indicative dose exceeds 0.1mSv/year, then Public Health England should be contacted for additional support.
See also the information note for regulation 11 for radioactivity monitoring.
Estimating volumes using population
Where information on volumes of water used is not available, an estimate can be made where the population supplied is known. Table 4 gives examples based on an assumption of 200 litres consumption per person per day.
Table 4: Estimating volumes using population
10 ≤ 100
> 50 ≤ 500
100 ≤ 1,000
> 500 ≤ 5,000
1,000 ≤ 2,000
> 5,000 ≤ 10,000
2,000 ≤ 3,000
> 10,000 ≤ 15,000
3,000 ≤ 4,000
> 15,000 ≤ 20,000
4,000 ≤ 5,000
> 20,000 ≤ 25,000
5,000 ≤ 6,000
> 25,000 ≤ 30,000
6,000 ≤ 7,000
> 30,000 ≤ 35,000
7,000 ≤ 8,000
> 35,000 ≤ 40,000
8,000 ≤ 9,000
> 40,000 ≤ 45,000
9,000 ≤ 10,000
> 45,000 ≤ 50,000
4 + 3 for each 1,000m3/day of the total volume
(rounding up to the nearest multiple of 1,000m3/day)*
Any water used for rearing livestock or irrigation can be excluded from the total volume of water used.
Table 5: likely causes of a parameter arising in a private water supply
Where aluminium compounds are used as coagulants in treatment.
Occurs naturally in some surface and groundwaters.
It can be derived from domestic plumbing fittings.
It can be present naturally in some groundwaters.
Contamination of raw waters from petrol/diesel etc.
Permeation of plastic distribution and domestic plumbing pipes.
Leaching from internal coal tar lining of some distribution pipes.
Contamination of surface waters with detergents mainly from sewage effluents.
Present in sodium hypochlorite used to disinfect water, including electrolytically generated hypochlorite. Formed if ozone used and water contains bromide. Can occasionally be found as contamination from industrial activities.
Leaching from galvanised pipes and some domestic plumbing fittings (e.g. plated taps).
Indicator of saline intrusion, so relevant in coastal areas. Also relevant if water softener installed. May indicate sewage pollution of surface water.
Leaching from some domestic plumbing fittings (e.g. chromeplated plastic taps). Can also occur as contamination from industrial activities.
Contamination of raw waters from sewage, sewage effluents and animal waste.
Leaching from pipes and plumbing fittings. Low pH and low or high alkalinity increases copper leaching.
Possible contamination of raw waters from industry (e.g. metal finishing, wood preservatives).
Volatile solvent used in manufacture of vinyl chloride and other processes. Can contaminate and persist in groundwater.
Contamination of raw waters from sewage, sewage effluents and animal waste.
May be present in some groundwaters.
Use of iron compounds as coagulants.
Occurs naturally in some surface water and groundwaters.
Corrosion of iron distribution pipes.
Leaching from lead pipes in distribution and domestic plumbing or from lead soldered copper pipes. Low pH and low or high alkalinity increases lead leaching. Present naturally in some groundwaters.
Present in some greensand filtration materials.
Occurs in some surface water and groundwaters.
Contamination from mercury thermometers and float valves
Leaching from some domestic plumbing fittings (e.g. plated taps).
Contamination of surface and groundwaters from fertilisers, animal wastes or sewage effluents.
Contamination of raw waters. Use of chloramination as a residual disinfectant or use of chlorine as disinfectant when ammonium ions present.
Contamination of raw waters from use in agriculture, forestry, roads, railways etc.
Pesticides – total
This means the sum of the concentrations of the individual pesticides detected and quantified in the monitoring procedure.
Leaching from internal coal tar lining of some distribution pipes. Sum of four individual PAH.
May occur naturally in some raw waters.
Present in raw waters but usually below standard. Can be introduced by water softeners and treatment chemicals (e.g. sodium hypochlorite for disinfection) or through saline intrusion of groundwaters in coastal areas.
Occurs in some raw waters, but usually below the standard.
Tetrachloroethene and Trichloroethene
Contamination of some groundwaters from use of these volatile solvents in dry cleaning and metal finishing. Standard is sum of two compounds.
Contamination of some groundwaters from use of this volatile solvent in metal finishing and other industries.
Trihalomethanes – total
Formed by reaction of organic matter in raw water with chlorine compounds used as disinfectants. Standard is sum of four compounds.
Total indicative dose (for radioactivity)
May be present in groundwaters where the underlying geology contains elevated levels of radon.
Contamination of raw waters from natural or manmade radioactive compounds.
Cosmic production in upper atmosphere. By-product of nuclear explosions and nuclear industry.
Use of polyacrylamides as coagulant aids.
Use of polyacrylamide grouts for borehole/well linings.
Use of polyamines as coagulant aids.
Use of epoxy resins (e.g. to line pipes and tanks).
Use to make some ion exchange resins.
Used for making PVC. Leaching from unplasticised PVC pipes used in distribution or domestic plumbing
Appendix 3 Special circumstances for monitoring
When a private water supply supplies a single drinking water fountain and no other premises, the local authority is required to monitor the supply at the fountain in accordance with regulation 9. When the private water supply supplies a drinking water fountain and other premises, the local authority should select a representative premise for sampling from all those supplied including the fountain. However, as the fountain represents the highest risk, it should be sampled at least once per year and, when it is sampled, the local authority should take a sample at the same time for microbiological parameters only (coliforms, E.coli and colony counts) from one of the other premises supplied by the supply.
Monitoring of supplies used only for toilet flushing
A private water supply to a premise used only for toilet flushing falls under the definition of domestic purposes under the Water Industry Act 1991 (section 218), on the basis that it is a sanitary purpose.
A risk assessment for the supply should be carried out to determine any health risks associated with that use, if there are any aesthetic issues which may affect its acceptability, or if there is a risk of contaminating any wholesome supplies. The Inspectorate has developed a risk assessment tool specifically for toilet flushing, which is available on the Drinking Water Inspectorate website. If the risk assessment confirms that there are no significant risks to health, routine monitoring is not required.
PWS Regulations 2016 (as amended) v.6, February 2021