The European Directive (98/83EC) relating to the quality of
water intended for human consumption (the Drinking Water Directive)
came into force in 2000. It applies to all water supplied for food
preparation, public and commercial activity and domestic purposes,
irrespective of the source of that supply. In the UK, for
historical reasons, the legislation differs for public supplies
(i.e. from a statutory water company) and private supplies (where
not supplied directly by a statutory or licensed water undertaker).
Amending the private water supply regulations has lagged behind
those for public supplies and the responsibility for monitoring
water quality differs. This Policy Position Statement outlines the
legislative background to monitoring private water supplies and how
this is working in practice.
CIWEM's Position on Water Quality of Private Supplies
1. Whilst water from some private supplies is wholesome,
this is less certain than with public supplies. Visitors should be
aware of which premises are not supplied by a statutory water
company. At present this is not easily recognized, except for
public premises in Scotland where notices should be displayed.
Regulating authorities should diligently find and monitor private
supplies used by the public and provide guidance to all owners,
users and visitors who are concerned about water quality.
2. The self-assessment form and technical manual prepared
by the Scottish Government, in collaboration with other UK
jurisdictions, should be updated once the private water supply
regulation have been revised in England and Wales and
3. The cost of treatment, especially to single dwellings
and small supplies, is probably the greatest hindrance to bringing
the water quality of private supplies up to the level of compliance
seen in public supplies. Many owners and their families have not
experienced illnesses linked to the water supply and can see no
reason to assess the risk of contamination or to pay for water
quality testing and subsequently installing treatment equipment.
Owners should be better informed of the risks and made aware of
grants available to install treatment. However, experience in
Scotland, where non-means tested grants are available, indicates a
surprisingly low rate of uptake of grants.
4. Advice to owners of private supplies to help them obtain
and operate equipment for treating or testing water at a reasonable
cost should be more readily available from non-commercial bodies
such as the local authority.
5. There is currently no regulatory instrument in the UK to
provide specific guidance on the proper installation, operation and
maintenance of UV disinfection systems for private water supplies.
This should be rectified in light of the recent amendment to the
Water Supply (Water Quality) Regulations which recognizes UV
disinfection as a relatively inexpensive and effective means of
inactivating Cryptosporidium that is suited to small systems.
6. Source protection is much more important for private
supplies than public supplies because treatment is often inadequate
or absent and the monitoring frequency is very unlikely to detect
deterioration before it is too late to prevent ill health. A proper
assessment of the risk of contamination is essential, followed up
with action to mitigate any unacceptable risks. This should either
be done by a trained person or the owner, with clear guidance from
the regulatory authority. The risk assessment should include the
intrinsic nature of the source, the likelihood of pollution and the
suitability of all materials in contact with water between the
source and the point of use.
The Chartered Institution of Water and Environmental Management
(CIWEM) is the leading professional body for the people who plan,
protect and care for the environment and its resources, providing
educational opportunities, independent information to the public
and advice to government. Members in 98 countries include
scientists, engineers, ecologists and students.
In the UK, for historical reasons, the legislation differs for
public supplies (i.e. from a statutory water company) and private
supplies (where not supplied directly by a statutory or licensed
water undertaker). As a consequence, two sets of Regulations, one
covering the public supplies and one covering private supplies,
were written to transpose the European Drinking Water Directive
(DWD) into UK law. Slightly differing Regulations were written for
the three jurisdictions of England and Wales, Scotland and N.
Ireland. Mineral waters and bottled waters are excluded from the
DWD as they are covered by other Directives and Regulations.
A private water supply may be less than 1 m3/d or serving a
single household. At the other end of the scale it can serve many
dwellings or commercial premises and provide wholesome water to
1000 people or more. The raw water may be obtained from a variety
of sources, including boreholes, wells, springs, rivers or lakes.
In many cases treatment is minimal or non-existent. The monitoring
requirements in the DWD vary according to the size of the
In N. Ireland it is estimated that less than 1% of water comes
from private supplies. The Inspectorate carries out an annual
survey to identify the private water supplies falling within the
Private Water Supplies Regulations. To date (October 2009), 12683
supplies have been identified, of which 1162 are dairy farms.
In Scotland around 1.5% of the population relies on private
supplies for their drinking water. Grants of up to £800 to improve
the supply are available from the local authority. The Grant Scheme
is not means tested and owners may be eligible for financial
- their home or business is in Scotland and served by a
private water supply;
- the private water supply is the main or sole source of water
for human consumption purposes to these premises; and
- the private water supply is in need of improvement to bring
it up to modern standards.
The detailed eligibility criteria are set out in the Private Water
Supplies (Grants)(Scotland) Regulations 2006.
In England and Wales about 1% of the population have private
water supplies to their homes. Most private supplies are situated
in the more remote, rural parts of the country.
The Drinking Water Directive (DWD) was revised in 1998 as
European Directive 98/83/EC, necessitating changes to the UK
regulations to implement the requirements of the Directive by the
end of 2000 and to comply with most of the standards in the
Directive by the end of 2003. Whilst the public water supply
regulations have been amended throughout the UK, in 2009 England
and Wales were still operating under the Private Water Supplies
Regulations 1991. A revised edition has been out for consultation
(all local authorities) and is due to be published in 2009. In
Northern Ireland consultation has been completed. Meanwhile, the
Private Water Supplies Regulations (Northern Ireland) 1994 remain
in force until the new regulations are in place in 2010. Scotland
have complied with the new Directive and issued the Private Water
Supplies (Scotland) Regulations 2006.
In Scotland, England and Wales the responsibility for monitoring
private supplies, keeping records, investigating risks to health
and reporting annually to the Secretary of State lies with the
local authority. In Northern Ireland a unit within the Northern
Ireland Environment Agency (NIEA), the Drinking Water Inspectorate
for Northern Ireland, regulate supplies that serve more than one
property or are used for commercial food production. The Drinking
Water Inspectorate (DWI) in England and Wales and the Drinking
Water Quality Regulator (DWQR) in Scotland have an advisory role in
relation to private water supplies This includes the provision of
technical advice and support to Local Authorities, on all aspects
of drinking water quality. All three regulators have signed a
Technical Manual (Scottish Exec. 2006) which is a reference
document for Environmental Health staff.
Many UK homes (over 1%) rely on a private supply. A very high
proportion of UK residents and visitors may be exposed to water
from private supplies when on holiday or engaged in everyday
activities such as going to a restaurant in the countryside or
buying food from a local market. Individuals who have compromised
immune systems and infants are vulnerable to changes from their
normal water quality. Without proper regulation of private
supplies, much of the population could be exposed to the risk
inherent in consuming unwholesome water at some time each year.
The mains water in the UK is of excellent quality as a result,
in part, of investment in the treatment and infrastructure of water
companies driven by strong regulation inaugurated at the
privatisation of the water industry in England and Wales. The
preparation of the Private Supplies Regulations and their
enforcement has lagged behind that of the public water supplies. In
consequence, the statistics published by the UK regulators each
year, to characterize the public water supplies, present an unduly
optimistic picture of water quality in UK if quoted out of context.
The report by DWQR for 2008 has summary information on private
supplies that demonstrates the unsatisfactory quality at many
premises in Scotland.
The vulnerability of the source to pollution will not be apparent
to owners unless they have been trained in such matters. Risk
assessment by an independent, trained surveyor is clearly
preferable, but expensive for a single householder where the cost
is not borne by the local authority. The owner of a source may be
more concerned about the potential cost of improving his supply
than the risk of illness. Where self-assessment is an option, the
owner must be given adequate guidance and advice. It would be
prudent for the authorities to audit a proportion of the
Materials of construction
The materials acceptable for use in public water supplies and
within buildings are governed by regulations and advisory schemes.
These do not extend to the collection and conveyance of raw water
from a private supply or to premises not connected to a public
water supply. There is potential of contamination through corrosion
or leaching from inappropriate materials which is best evaluated
whilst undertaking a risk assessment of the supply. Any
assessment of the suitability of must take into account the source
water quality such as the pH.
Maintaining treatment processes
Where equipment has been installed it is important to know that it
is operating effectively. Dosing systems that have run out of
disinfectant or a UV unit with fouled surfaces or aged lamps will
not provide the protection expected. Granular activated carbon
(GAC) contactors and filters will not work efficiently when run
beyond their design life, and worse, may increase the
Owners should be made aware of the maintenance requirements when
installing treatment equipment and this must be passed on to a new
owner when the property changes hands.
The water from private supplies, as with water supplied by pipe
from a statutory undertaker must be wholesome, in that:
- it must conform to the standard set out in the European
Directive on water for human consumption and where more stringent,
the national criteria;
- it must be treated in a manner appropriate to the water
- processes and materials used in its treatment and conveyance
must be suitable.
Private water supplies to a single dwelling that is not open to
the public are exempt from some requirements of the 1991
regulations and the draft 2008 regulations in England and
Wales. In Scotland, Type B supplies, which are <10m3/day,
serve <50 people or are not supplied as part of public
commercial activity are exempt from some of the requirements of the
2006 Regulations. Whilst it is accepted that the risks to health
are low, it should be clear to people visiting dwellings with a
private supply that the drinking water may not have been tested to
the rigorous standards they expect of public water supplies. In
Scotland premises used by the public are required to display a
notice informing visitors about the water supply.
Water quality testing of private supplies is less frequent, but
in accordance with the Directive, and they are not as
comprehensively monitored as public supplies. This is justified as
a risk-based approach to keep the cost of monitoring within
reasonable bounds and to ensure that the risk is adequately
managed. Local authorities in England and Wales are charged with
carrying out a risk assessment of every private supply every five
years. Experience in Scotland indicates that each risk assessment
takes approximately one day. This is not required for supplies to a
single dwelling unless the owner or occupier requests one. The
costs can be recovered from the person requesting the assessment or
sampling in accordance with the fees set out in the Regulations.
The Scottish Government, in collaboration with outher UK
jurisdictions, has produced a self-assessment form and
technical manual to help owners of small supplies complete the form
themselves. This Manual is intended to be used throughout the
Traditionally owners of remote properties have relied on a
'pure' water source, typically a spring or shallow well, without
any treatment. Where this was not possible, some form of simple
filtration has rendered the water clear with an acceptable taste.
Despite appearances, clarity, odour and taste are insufficient to
judge the wholesomeness of the supply. Simple chlorine dosing or a
silver impregnated ceramic filter are commonly used to disinfect
water, but chlorine-resistant Cryptosporidium has increasingly been
found in public supplies where chlorine is the only disinfectant.
Alternatives, such as UV irradiation, are needed as cheap, low
maintenance packages for the general public if the risks of
infection are to be reduced.
Whilst an untreated supply may be satisfactory for much of the
time, it can become polluted in exceptional circumstances. The most
common cause of pollution is probably high rainfall events which
either flood an underground source with surface water or introduce
contaminants through run-off from surrounding fields. Owners may
not be aware of this and so it may be missing from the risk
Obtaining any type of equipment for treating or testing water is
not easy, and rarely cheap, for a small home owner with no
knowledge of the subject. CIWEM see this as an impediment to
widespread installation of treatment in privately owned
CIWEM is pleased to see that in England and Wales and in N
Ireland the confusing division of private supplies into eleven
classes for the purposes of monitoring has been dropped from the
2009 revisions in favour of a simpler system based on the estimated
References / Further Reading
Websites: DWI, DWQR, NIEA for guidance and links to the
Scottish Executive (2006) Private Water Supplies:
Technical Manual, ISBN: 0-7559-5151-4 Published by the
Camm, R., Ferrere, P., Hall, T., and G. Stanfield. (2008). UV
Inactivation of Cryptosporidium. UK Water Industry Research (UKWIR)
Report 08/DW/06/20. UKWIR, Queen's Gate, London.