Requirements, Regulation and Legislation


Bottled Water

Where alternative water supplies are provided through bottled water (in emergencies or associated with planned interruptions) then a water undertaker must be able to demonstrate that the bottled water meets the relevant requirements of the Regulations.

In times of emergency or associated with planned interruptions, alternative water supplies may be provided through bottled water. The bottled water must meet the requirements of the Regulations.

When a water undertaker intended to supply bottled water, they must ensure that procedures are in place to provide assurance in water quality throughout the whole chain of supply:

- bottled water that is stored locally should be kept in a dark cool location (or using covers that protect it from direct sunlight).

- it should be store away from fumes and strong smelling substances.

- all bottles must clearly show the use by date, and the date must be adhered to.

If the quality of the water is known to have deteriorated, then procedures should be in place to recall those batches.

For more information please click here for the Technical Guidance (TGN11) or here for guidance note 8.4

Clothing and tools

Protective clothing that is worn on restricted operations should be colour coded and kept clean and separate from other protective clothing.

Soiled clothing that has been worn on wastewater operations should never be worn in areas of restricted operations.

Tools should be similarly kept clean and protected from contamination. Water and waste water operations should have separate tool sets, and be clearly colour coded to help distinguish between them.

For more information please click here and see guidance note 2.5

Competent Operator

An essential element of water quality assurance is the operation of water treatment processes by competent personnel.

Representatives from the DWI, EUSR and UK water companies agreed on a framework for competency standards required for ‘operators’ working with water treatment works. It states that assessment and training is undertaken against the National Occupational Standards (NOS) for operating process plant. In house schemes may be adopted but must be mapped against the NOS and require approval by EUSR as the Water Industry’s standard setting body.

The frameworks sets out that all operatives are assessed and in receipt of required training before they can be declared as competent.

For more information please click here and see guidance note 6.6

Contamination by backflow

Backflow of water from customers' installations or via air valves and other distribution fittings into the mains can be a source of serious contamination.

Backflow of water from air valves or customer’s installations can be a source of acute contamination. It can occur when pressure drops or is low, where high presume installations in customer’s premises overcome mains pressure, or when mains are isolated for work.

Fittings must be installed correctly to decrease the likelihood of contamination. The fittings used must be meet The Water Supply Regulations to help prevent contamination. The Water Regulation Advisory Scheme (WRAS) are available for guidance.

Water undertakers are required by law to enforce the requirements of the Regulations and have the power to enter premises to inspect installations and ensure that they meet the requirements. Where a site is deemed to be a high risk (i.e. farms etc.) a programme for inspecting installations should be maintained.

For more information please click here and see guidance note 8.3.

Distribution systems: Design criteria

When designing a distribution system, a number of things should be kept in mind at all times: They should be designed to prevent the deterioration of treated water as it flows through; they need to remain under positive pressure at all times; dead-ends should be kept minimal, but where they cannot be avoided, ensure that facilities to flush have been provided.

Care should also be taken when designing chambers: the chambers for air valves should be situated above the level surface water may rise to; the air valve chambers as well as chambers for other valves, hydrants and meters should be drained when possible to prevent the submergence of any fittings.

Whenever work stops for a long period (i.e. at night), the pipe should be capped at the end to prevent contamination or ingress.

For more information please click here for the Technical Guidance (TGN12) or here for guidance note 8.1.

Final disinfection

Water undertakers must have disinfection policies in place to ensure that all drinking water is effectively disinfected prior to supply as per the Regulations. Failure to effectively disinfect drinking water can be serious and pose a potential risk to public health.

In the UK, chlorine is used most commonly for the final disinfection; however, other processes may also contribute to the overall disinfection.

When disinfecting with chlorine, monitors should be installed in the disinfection system. Suitable monitoring points include: After the contact tank, after chlorine dosing and mixing, and where the water exits the treatment works.

Appropriate alarm levels should be in place with robust procedures and systems to ensure that water that has not been disinfected does not enter the supply.

To ensure that the process isn’t compromised, water entering the disinfection final stage should be adequately prepared. WHO provides guidance relating to contact times for chlorine in regards to pH and temperature, and the turbidity of water would not be greater than 1 NTU as set out in the Regulations.

For more information please click here for the Technical Guidance (TGN8) or here for guidance note 6.2

Ground water sources

To prevent ingress of surface water, boreholes and wells should be lined adequately and sealed; and collection chambers and other headworks of springs should be maintained and designed with prevention in mind. Inspections should be carried out regularly of all seals and linings.

Activities undertaken within Source Protection Zone 1 should be given particular attention, where the severity and immediacy of the contamination impact is likely to be highest. Enhanced monitoring and risk assessments should be carried out where the overburden is permeable or where there are sources of groundwater near or on top of the stratum used for drawing water.

For more information please click here and see guidance note 5.1

Hygiene training

All individuals working on restricted operations must have been trained and authorised under the National Water Hygiene Scheme.

Cards issued under the Scheme are valid for 3 years. Repeat training and authorisation is required for card renewal. The Scheme card must be carried at all times by any individual working on restricted operations.

It is recommended that regular audits are carried out to ensure all individuals working on restricted operations are in possession of a valid scheme card. Any individual who cannot produce their valid scheme card within a reasonable timescale should be suspended from undertaking restricted operations.

Individuals who flagrantly or repeatedly breach the standards required by the Scheme in the course of their duties should be suspended from carrying out work on restricted operations and their scheme authorisation may be temporarily revoked whilst appropriate retraining is undertaken. Details of the National Water Hygiene Scheme can be found on the EU Skills website

In addition to the scheme, it is recommended that water undertakers carry out additional detailed training in respect of specific restricted operations tasks such as mains disinfection, flushing and sampling.

Hygienic practices in the Water Industry

Water is food. Most food products require water as an ingredient or as part of the preparation process. Therefore, the Water Industry is the largest food producer in the UK. Just as food must be handled and prepared hygienically, the same must be expected of water.

Thinking of water as food is useful in enforcing the required steps that must be taken to prevent contamination of water during operation, repair and maintenance of equipment, plans and installations.

All persons involved in restricted operations, or undertaking work near restricted operations, must be registered on the National Water Hygiene Scheme (see our Water Hygiene course pages), and carry a water hygiene training card.

For more information please click here and see guidance note 2.1

Mains repairs

When repairing mains, the work should be undertaken without full depressurisation wherever possible, this helps to prevent ingress. When full depressurisation is unavoidable, dewatering facilities must be made available on site.

Risk assessments should be carried out to evaluate the potential for contamination resulting from burst or leaking mains and the repair process involved. The assessment should determine the subsequent necessary precautions required to protect human health.

The precautions should include the need to disinfect the repaired main before returning to supply. In cases where the repaired main must be returned to supply before satisfactory analysis and disinfection, issuing advice to the customers who might be exposed to contaminated water should be considered.

For more information please click here for the Technical Guidance (TGN3) or here for guidance note 8.1.

Management of events that could potentially affect human health

Water undertakers must have in place procedures to react to any even that affects/has the potential to affect the quality of drinking water.

Any detection of significant deterioration in the water quality (at any stage) that could potentially impact adversely on human health must be reported urgently. Management procedures should be in place to deal with such events.

The Drinking Water Inspectorate website ( contains guidance on the type of events that are to be notified.

The duty of care for the protection of consumer’s health is ultimately the responsibility of the water undertaker. But any restrictions on water use should be jointly agreed with health professionals. Procedures for warning consumers as soon as possible in the event of water restriction should be in place.

Outbreak Control Plans (OCPs) should be in place with Water undertakers and regularly reviewed and developed collaboratively with Health Protection Units and Local Authorities. To prevent a recurrence following any significant event affecting the drinking water quality, reviews should be undertaken to identify any changes that are necessary to the working practices and procedures.

A report carried out by the DWI and HPA following the quantity of large-scale water quality related episodes between 2007 and 2008 is available on their websites. The report provides guidance to both health and water professionals to support water quality risk assessments and also the issuing of consumer protection advice.

For more information please click here for the Technical Guidance (TGN10) or here for guidance note 10

Materials in contact with water

Water quality problems can arise from the use of inappropriate materials in contact with water. To reduce this risk, materials in contact with water intended for human consumption must meet the requirements of the Regulations (e.g. Regulation 31 of the Water Supply (Water Quality) Regulations 2016 in England or equivalent in devolved administrations).

To decrease the risk of inappropriate materials coming into contact with water and causing problems with water quality, all materials used in water systems intended for human consumption must meet the Regulations requirements set out in Regulation 31.

The process for the approval of any new materials/products is managed by the DWI or Drinking Water Inspectorate. Further advice on appropriate materials and approval is available on their website.

For more information please click here and see guidance note 9

Measures to prevent deterioration or contamination

Tanks that will contain treated water meant for supply should be designed, operated and maintained in such a way as to prevent any potential contaminants of surface water from being able to ingress. All livestock should be kept away from the tanks, and measures taken to prevent other animals from being able to access the tank.

Unauthorised access should be prevented according to the security standards set by the water industry and complying with the 2006 Security and Emergencies Direction.

To prevent stagnation of the stored water, tanks and their parts should be designed in a way to aid the circulation of the water.

To identify any possible ingress of surface water or contaminants, regular inspections (both internal and external) should be carried out on the tanks by competent personnel. Any materials used to repair or maintain the tanks must meet the standards set in the Regulations. It is suggested that the maximum amount of time between internal inspections should be no more than 10 years, but the frequency is determined by risk assessments and should be appropriate to the design and condition of the tank.

After inspections, the service reservoirs must be fully cleaned and disinfected before being used again.

For more information please click here for the Technical Guidance (TGN9) or here for guidance note 7.1.

Medical surveillance of personnel

All individuals who are registered on the National Water Hygiene Scheme and are in possession of a Water Hygiene Training Card, will have undergone initial medical assessment.

Procedures must be in place to ensure that if personnel working on restricted operations develop symptoms of infectious diseases, they report it to their supervisors as well as seeking advice from a medical professional. Personnel suffering from illnesses such as infective jaundice, persistent diarrhoea, prolonged unexplained fevers, or gastroenteritis should be excluded from working on restricted operations until a medical advisor has given them clearance. It must be a matter of record.

For more information please click here for the Technical Guidance (TGN1) or here for guidance note 4.

Monitoring water quality

The monitoring of water quality is necessary to ensure that the treatment process as a whole is able to continue to achieve the water quality required, that treatment processes are optimised adequately, and as a means of validating and verifying the control measures in place.

Continuous monitoring should be undertaken for key parameters critical to the treatment process employed and sampling should be at a sufficient frequency, and for appropriate determinands, in order to establish and confirm the general water quality and identify significant variation (such as seasonal variation, etc.). Any unexplained deterioration in quality should be investigated and acted upon.

Some raw water sources are prone to rapid changes in quality due, for example, to heavy rainfall and the nature of the catchment or aquifer. Continuous monitoring of relevant parameters (e.g.: turbidity) should be considered, to provide early warning of water quality changes and to assist in the control of water treatment processes.

The Regulations give statutory minimum frequencies for monitoring the quality of final treated water.

Water undertakers should consider the need for additional operational monitoring of water during its treatment, to confirm the satisfactory operation of the treatment processes and in distribution, to provide sufficient information regarding water quality generally and to give early indication of any developing deterioration in the quality of supplies.

For more information please click here for the Technical Guidance (TGN15) or here for guidance note 6.1

Multi-functional working

It is advised that the number of personnel required to work on both sewage and water installations is kept to a minimum to reduce the contamination risk.

If personnel are required to work on both wastewater and clean water installations it is highly important that the risk of cross contamination is minimised by appropriate procedures.

These include the following minimum requirements:

- individuals undertaking multi-functional work must be properly trained and authorised

- have access to colour coded and separately stored sets of clothing, footwear and tool kits

- if separate tool kits is not possible (and risk assessments have been performed) then satisfactory cleaning and disinfection facilities should be made available.

For more information please click here and see guidance note 2.3

New mains

To prevent contamination or ingression, all pipes and fittings for new mains must be stored and transported out of direct contact with the ground.

Open pipe ends should be capped/protected whenever work stops for an extended period; and reasonable measure should be taken to ensure the pipes are protected from contamination during laying.

New pipes should be pressure tested and disinfected before they are brought into service.

Once a new main has been laid, samples should be taken and analysed to ensure that they meet the requirements set by law.

For more information please click here for the Technical Guidance (TGN2) or here for guidance note 8.1.

Out-of-service and abandoned mains

If mains have been out of service (for an extended period of time) before recommissioning, tests should be undertaken to check whether there is any significant deterioration to the water quality. These tests should include flushing, sampling and analysis with the consideration of further disinfectant.

Abandoned mains and fixtures should be disconnected from the remaining pipework as soon as possible so that contamination and deterioration can occur. If valves and stopcocks are to be left in situ, they should be locked so they cannot be opened accidentally. Clear records should be kept to identify where abandoned mains and assets have been left in the ground.

For more information please click here for the Technical Guidance (TGN5) or here for guidance note 8.2.

Plant maintenance

An integral part of plant maintenance is hygiene, and its importance should be included into any maintenance contracts.

Process plants should be inspected and maintained, and competent personnel should carry out servicing and calibration on monitoring and chemical dosing equipment at appropriate intervals.

Appropriate risk assessment and identified controls should be implements prior to any maintenance activities that might have a negative effect on water quality.

Standby chemicals, fuel and plan required for treatment facilities should be regularly assessed to determine operability.

Prevention of animal access should be included in maintenance.

For more information please click here and see guidance note 6.4

Plant security and supervision

Strict supervision should be enacted when water treatment works have visitors, and no unnecessary access should be given to restricted areas associated with fully or partially treated water.

Remote and unattended water installations can be vulnerable to deliberate interference.

Necessary steps should be taken to prevent access by unauthorised personnel by careful premises design and appropriate security or detection in accordance with the current water industry security standards.

For more information please click here and see guidance note 6.5

Preparing water for disinfection

The regulations states that drinking water must be prepared for disinfection adequately. There must be disinfection policies in place to achieve this at all treatment works. Failure of disinfections represents a risk to public health and is serious.

Water treatment processes should be matched to the quality characteristics of the water source and be capable of producing adequately treated water for all the expected variations of raw water quality, taking into account all known hazards within the catchment. Where this is not practicable or economic, an alternative strategy during periods of poor raw water quality is necessary e.g. reducing output of treatment works or temporarily taking the works out of service with provision of alternative supplies of adequately treated water. Risk assessments should inform the necessary control and monitoring requirements to identify such deterioration in raw water quality so that mitigating actions can be taken prior to any deterioration in treated water quality.

Treatment processes should be monitored to detect any failure or deterioration in performance as soon as possible. Plant used in the treatment of water should be designed and operated to prevent unsatisfactory water leaving the works in the event of failure. Failure and warning alarms should be relayed to an appropriate control centre, where they should be immediately assessed immediately and prioritised by competent personnel.

Where treatment works operate unattended for part or all of the time, the key processes such as clarification, filtration and final disinfection should be continuously monitored, with recording of appropriate process performance and water quality parameters. Automatic failsafe shutdown systems should be in place to prevent water which may represent a risk to human health entering supply.

It is crucial that water treatment is able to effectively remove particles and to prepare water for final disinfection so that the disinfection is not compromised. The Regulations require all water for public consumption to be disinfected prior to supply AND that such water is presented for the final stage of disinfection having a turbidity of less than 1 nephelometric turbidity unit (NTU).

Further important information in respect of the performance of processes designed to remove particles e.g.: Cryptosporidium) during water treatment can be found in reports by Sir John Badenoch and Sir Ian Bouchier (of which the report from the latter is available from the DWI website) and various UKWIR technical reports.

For more information please click here for the Technical Guidance (TGN13). 

Recreation and public access

It is the statutory duty of all water undertakers that the recreation and nature conservation are accounted for in the management of land that is under their control.

Due regard for the protection of water supply quality should still be given whilst enacting this duty. If the public has access, then arrangements should be in place to ensure the protection of water quality. This can be done by ensuring that waste from toilet facilities is disposed of satisfactorily, and also controlling the types of permitted activities.

For more information please click here for the Technical Guidance (TGN7) or here for guidance note 5.2

Storage of pipes and fittings

Fittings and pipes that are to be used in water supply should be protected from contamination and ingress by the use of end caps and stored above ground level.

Any pipes and fittings that might have become contaminated should be cleaned thoroughly and disinfected appropriated prior to use.

For more information please click here and see guidance note 2.9.

Tankers, bowsers and other bulk water containers

Any tankers, bowser and other bulk water containers should be assessed to ensure that they are protected from contamination and meet the regulatory requirements before they are used.

If a tanker or bowser is storing water for more than 48 hours, they must be monitored for electrical conductivity, pH and E. coli. If a tank is in use for longer than 96 hours, even more comprehensive chemical and microbiological analysis will be required. This testing must be conducted every subsequent 48 hours that the tank is being used. However, if the tank is refilled, emptied or replaced earlier than the 48 hour period, then no monitoring is required.

Tankers and bowsers must be constructed using materials that meet the requirements of Water Regulation 31.

For more information please click here for the Technical Guidance (TGN12) or here for guidance note 2.6.

Toilets and washing

Adequate toilet and washing facilities should be provided to enable all persons working on restricted operations to maintain high levels of personal hygiene.

This is especially true of temporary arrangements, wherein all waste must be disposed of without risk to the environment or water supply. For this reason, it is essential that vehicles being used on restricted operations are equipped with facilities for hand-washing.

For more information please click here and see guidance note 2.4.

Treated (or partially treated) water reservoirs and tanks

Storage tanks for treated water can be at risk of contamination through ingress. It is the responsibility of the water undertaker to ensure that the operation and design of water storage facilities minimises the risk of deterioration of the quality of the water.

A variety of other factors can lead to a potential deterioration in water quality, these include:

- ingress of surface water (or other contaminants like faecal matter) through roof joints or ancillary services i.e. cable ducts

- stagnation , which can lead to the potential for microbiological regrowth

- accumulation of particulate material

- contamination by deliberate interference or vandalism

For more information please click here for the Technical Guidance (TGN9). 


Any person involved in the use and deployment of bowsers and tankers should hold a National Water Hygiene Card. If the tanker driver has any contact with the equipment that is to be used, including associated fittings, then they will also require a National Water Hygiene Card.

Vehicles that are used directly for water supply purposes (or in support of), should be solely used for those purposes. Vehicles that are used in restricted operations should have particular attention paid to their cleanliness. Water Undertakers should ensure that tankers and bowsers used in conveying potable water have been protected from contamination during use.

Any vehicle that has been used to carry or handle sewage (or sewage sludge/spray) should only enter restricted sites for specifically approved purposes.

All tools and fittings that are used on restricted operations should be kept in separate areas of the vehicle and stored hygienically above the floor. Particular care should be paid to the storage of fuel/oil and other similar chemical, as there is a high potential for contamination. Pipes being transported should be end-capped and stored above the floor of the vehicle. Any soiled/used equipment should be thoroughly disinfected before being reused.

Vehicles should always carry hand washing facilities; either soap and water, or hand sanitizer and paper towels.

For more information please click here for the Technical Guidance Note (TGN12).

Water treatment chemicals

Water Supply Regulations 2016 states in Regulation 31 the requirements that all chemicals used in conjunction with water and its treatment must meet. All products should be used according to the manufacturer’s information and guidance.

Clearly defined chemical storage facilities should be in place, and procedures should be enacted for the procurement, delivery, receipt and usage of chemicals for water treatment to keep accidental contamination of the water supply from happening.

All chemicals used in the treatment of water will have specified shelf lives, the storage of these chemicals should be managed with these expiry dates in mind.

Containers should be labelled clearly and never used to store any alternative fluids or chemicals.

For more information please click here and see guidance note 6.3