A. The Water Supply (Water Fittings) Regulations and Scottish Water Byelaws require domestic water supplies to be adequately protected from backflow.
These regulations and byelaws define Fluid Risk Categories by the type of contaminants which may be present, and take into account the risk of harm to human health which may be caused. They also specify appropriate types of prevention devices which must be fitted to guard against backflow.
Backflow prevention devices must be fitted between the domestic plumbing system and the source of the potential contamination.
The table below give a simple overview of the fluid categories and typical backflow protection devices which could be used.
Please note this is not a comprehensive or exhaustive list.
| Fluid Category – risk to health | Typical device which may be used |
| 1. – drinking water - no risk | No backflow prevention device needed |
| 2. – slight change in taste, odour or temperature – slightly unpleasant | Single check valve |
| 3. – chemicals of low toxicity – slight health hazard | Double check valve |
| 4. – toxic chemicals or carcinogenic substances – significant health hazard | Reduced Pressure Zone (RPZ) valve or break cistern incorporating a Type AF air gap |
| 5. – radioactive or very toxic substances, faecal and pathogenic organisms – serious health hazard | Break cistern incorporating a Type AA or AB air gap |
A. The Water Supply (Water Fittings) Regulations and Scottish Water Byelaws require that water or water-using equipment used with fluids or materials which could contaminate it must have adequate protection. This protection is to stop potential contaminants getting into other parts of the system, especially drinking water.
What is it?
Backflow is the term used when fluids travel back towards the source - contrary to the direction which was intended.
How does it happen?
It can happen in one of two ways:
1) Fluctuations in water pressure can cause a lowering, and in some cases, a negative pressure or vacuum to occur in the water supply. This may result in fluids upstream being syphoned or sucked, back into other parts of the system. The fluctuations can occur when carrying out repairs or where there is high usage on the system. This is known as back-siphonage.
or possibly
1) Where fluctuations in water pressure - such as those that occur when carrying out repairs or where there is high usage on the system - can cause a lowering, and in some cases, a negative pressure or vacuum to occur in the water supply. This may result in fluids being syphoned or sucked, back into other parts of the system. This is known as back-siphonage.
2) Where the pressure in the system downstream is greater than those upstream, fluids can be forced back towards the source into other parts of the system. This is known as back-pressure.
Once fluids are in a water system they can be re-distributed to other parts of the system and in some circumstances back into the public mains.
A. Yes - Any shower hose that reaches into a toilet bowl or into a bidet is a fluid category 5 risk of contamination to your drinking water supply. There are several ways to eliminate the problem such as constraining the hose with a clip so that it cannot reach the WC or bidet, fit a fixed shower screen or simply fit a shorter hose. For further advice look at our bathroom guidance.
The Water Supply (Water Fittings) Regulations and Scottish Water Byelaws only specify two situations where wholesite protection may be required or considered necessary.
1. To prevent backflow between separately occupied premises, an example could be in blocks of flats or other buildings of multipleoccupancy such industrial units or shopping arcade.Your local water supplier is best placed to advise on the situations which may require additional protection.
A. A check valve is specific type of valve which can prevent backflow from occurring. It has to be tested and meet very strict criteria, which ensures fluids are not able to be siphoned back into drinking water systems.
Non-return valves, often similar in design to check valves, are not able to meet this strict criteria.
A. Yes - You do need to duct or sleeve hot and cold pipework, to ensure that the pipework is accessible and/or can be removed for maintenance or repair. For further advice look at our guidance on concealed fittings.
A. There are minimum and maximum depths at which service pipes should be laid:
If you wish to install the service pipe either deeper or shallower than these depths you must notify the local water supplier for permission.
Important note: The gas service should be at 600mm to ensure separation from the water service pipe.
A. External water supplies can be subjected to localised climatic conditions which may require specific precautions – it is best to talk to the local water supplier about any specific requirements they may have.
A. This type of work could prevent access for repair and maintenance.
It would be normal for the existing water pipe to be either re-routed around the new extension, maintaining accessibility, or for it to be installed in a duct so that it can be easily removed thereby enabling it to be maintained or repaired in the future. However there may be local restrictions and you should contact your water supplier to ensure you are aware of these.
A. Blue MDPE plastic pipe is designed for below ground use, however it may be used above ground in situations where it is not exposed to light and is protected against:
A. The purpose of sealing ducts is to protect the property from the ingress of gas or vermin, or if they are between floors of a building to provide a fire break.
There are many site specific factors which have to be taken into account when deciding on the appropriate method of sealing ducts. Contact your water supplier for advice and to discuss your proposals to ensure no adverse consequences occur.
A. So far as is reasonably practical the temperature of water within cold water pipes should not be warmed above 25°C and ideally not above 20°C. Adequate measures should be taken to ensure that this temperature is not exceeded.
A. Building Regulations and not the Water Supply (Water Fittings) Regulations or Scottish Water Byelaws set the requirements where thermostatic mixing valves need to be installed.
However as with all water fittings they will need to meet certain standards of construction and from materials which are suitable for use with wholesome water.
A. Yes – The installation of a towel radiator or warmer on a domestic hot water system is acceptable provided that:
(a) The radiator, valves and any other fittings used to make this connection are manufactured from materials which are suitable for use with wholesome water, such as stainless steel or copper; and
(b) Adequate flow through the radiator is maintained at all times, and under no circumstances should the hot water in the radiator be allowed to stagnate; and
(c) The system design has taken into consideration the guidance given in clauses G18.2(1) and G18.4(2) (of Defra’s Guidance) for hot water distribution temperatures. This being the case it is likely that such a radiator can only be installed on the return of a domestic hot water system.
Defra Guidance
(1) G18.2 Hot water should be stored at a temperature of not less than 60°C and distributed at a temperature of not less than 55°C. This water distribution temperature may not be achievable where hot water is provided by instantaneous or combination boilers.
(2) G18.3 The maintenance of acceptable water temperatures may be achieved by efficient routing of pipes, reducing the lengths of pipes serving individual appliances and the application of good insulation practices to minimise freezing of cold water pipes and to promote energy conservation for hot water pipes.
A. Defra’s guidance G18.2 recommends that hot water should be stored at a temperature of not less than 60°C and distributed at a temperature of not less than 55°C. This water distribution temperature may not be achievable where hot water is provided by instantaneous or combination boilers.
Where practicable hot water should reach your tap within 30 seconds and be at least 50°C after fully opening it. This criteria may not be achievable where hot water is provided by instantaneous or combination boilers.
A. There are no specific requirements, however to prevent an undue waste of water, government guidance recommends that when opening a hot water tap, or other outlet, the water should reach 50°C within 30 seconds.
A. There are no specific requirements to install servicing valves to taps, but some manufacturers may require them to be fitted so check their installation instructions. That said it is good practice to do so as it allows maintenance to take place without disrupting the water supply to the rest of the property.
A. The Water Supply (Water Fittings) Regulations and Scottish Water Byelaws do not set requirements for waste pipework. This is normally controlled through Building Regulations.
A. Requirements for drainage systems are covered by Building Regulations and not the Water Supply (Water Fittings) Regulations or Scottish Water Byelaws. The enforcement of Building Regulations fall under the jurisdiction of local authority’s Building Control departments, and they are best place to give any advice.
A. The Water Supply (Water Fittings) Regulations and Scottish Water Byelaws do not cover this type of use or set any requirements.
Here are some organisations who may be able to help:
A.Yes – But it must be suitable for this purpose, it should capable of meeting the higher performance requirements for this purpose.
A. Where water is allowed to stagnate there is a risk of contamination. Pipework serving fittings which are redundant or been removed should be disconnected at source.
A. No - The Water Supply (Water Fittings) Regulations and Scottish Water Byelaws do not require lawfully installed fittings to be modified or removed.
However it is widely recognised that lead can have a harmful affect and most water supplier’s recommend and encourage the replacement of old lead pipes.
If you are concerned about lead in drinking water talk to your water supplier.
As far as is reasonably practical water within cold pipes should not exceed 20°C. The relative positions of cold water pipes to hot water pipes should be such that the cold water pipes are not warmed.
Wherever possible horizontal cold and hot water pipes should be fixed so that the hot water pipe is at a higher elevation than the cold water pipe (see diagram).
A. Yes - Pumps are allowed to be installed on supply pipes. However if the pump is capable of delivering more than 12 litres per minute, you must notify your water supplier and seek their consent before starting any work. Notification Page >>
A. Yes - Nothing required within the Water Supply (Water Fittings) Regulations and Scottish Water Byelaws prevents these flexible pipe connectors being used. However you do need to make sure that the materials the ‘flexi-pipe’ is made from are suitable for use with drinking water, particularly non-metallic materials. Like hoses these are known to be the cause of some water quality problems.
If you are thinking of using these, be aware that in some facilities, such as hospitals, may have a policy which sets restrictions or prevents their use – it is worth checking the job specification before you decide to install them.
A. In relation to stop taps the Water Supply (Water Fittings) Regulations and Scottish Water Byelaws set 2 requirements.
A. The Private Water Supplies Regulations set requirements for private sources of water. With the exception of Northern Ireland, Local Authorities are responsible for checking the safety and sufficiency of private water supplies in their area - normally by the Environmental Health departments. In Northern Ireland this is the responsibility of the Drinking Water Inspectorate at the Department of the Environment.
The Water Supply (Water Fittings) Regulations and Scottish Water Byelaws only apply to properties where the water is provided from the public supply – this includes properties with a private water supply which have a mains water backup supply. These regulations and byelaws do provide a useful code of practice for installation and backflow prevention requirements for private water supplies.
A. The Water Supply (Water Fittings) Regulations 1999 give two routes to demonstrate that a water fittings are an appropriate quality or standard.
More guidance can be found here
