Alternative Water Systems Information Leaflet and Guide

Transcription

1 Alternative Water Systems Information Leaflet and Guide

2 Contents 3 Introduction 3 What do we mean by alternative water? 3 Rainwater harvesting what is it? 3 Greywater how is it different? 3 What other sources can be used? 4 Standards and regulation 4 Are there any standards? 4 What regulations apply? 4 Notification to Water Companies 4 Do I need to tell the local Water Company about my installation? 5 System designs 5 Direct systems 5 Indirect systems 6 Back-up water supply 6 What happens when there is no rain? 6 What would happen if there was no mains water back-up supply? 7 Backflow protection 7 What sort of risk are alternative waters? 7 What backflow protection is required for the mains water back-up supply? 7 Clothes washing machines 7 Examples of backflow protection 8 Dead legs 8 Additional protection 9 Pipework 9 Do I need special pipework? 9 Below ground pipework. What should I use? 9 What about contaminated land? 9 Above ground pipework. What should I use? 10 Labelling and marking 10 Why do I need labels? 10 Colour coding pipework 10 Why must you colour code all water alternative pipework? 10 The following methods are recommended: 10 Commercial/Industrial pipes 10 Domestic pipes 11 Labelling 12 Maintenance 12 Do these systems need maintenance? 12 Summary 12 Other references 12 Acknowledgements 2

3 Introduction Alternative water sources are more commonly being considered for use in homes and business premises as customers become more Waterwise. In recent years the Water Industry has become aware of an increasing level of alternative systems, particularly borehole supplies and rainwater harvesting units, that have been installed incorrectly or have not been adequately maintained, leading to serious public health risks at the properties involved, and potential wider risk to public water supplies. The following guidance covers the key areas which must be adhered to and areas that need careful consideration for anyone designing installing and using these systems. What do we mean by alternative water? Alternative water covers a wide variety of sources from bore holes, river water, industrial process water, as well as Water Reuse systems. Water Reuse is the new term for what we used to know as water recycling or reclaimed water, and covers rainwater harvesting as well as greywater treatment. The purpose of these systems is to provide an alternative to mains drinking water that can be used for processes, or appliances that do not need such high quality water, as promoted in the 2010 revision of Part G of the Building Regulations. This allows for non-wholesome water to be used for the first time, thereby trying to help reduce the reliance on public mains water. The most common systems used in the UK are rainwater harvesting, greywater treatment, and bore holes. Rainwater harvesting what is it? In simple terms it is a means for diverting rainwater that falls on roofs, or other collection surfaces of a property, and storing it, usually in an underground tank, for later reuse. Collected rainwater will contain traces of atmospheric and environmental pollutants, and is likely to contain some animal and bird faecal matter. The extent of such contamination will vary from site to site but some degree of contamination must always be assumed. Greywater how is it different? Greywater is the wastewater from domestic pipes and fittings in our homes and businesses, but excludes the wastewater from toilets and urinals, which is known as blackwater because it is likely to contain faecal matter, and bodily wastes. Greywater can be sub-divided by the source, kitchen greywater is likely to contain high levels of fats, greases and organic matter, whereas bathroom greywater is the less polluted greywater from baths, showers and wash hand basins and it is this bathroom greywater which is normally collected for treatment and reuse. What other sources can be used? There are a great many sources of water that can be used, but it is often the amount of treatment needed to bring it up to a suitable safe level that limits its use. Whilst in most cases groundwater sources are relatively clean and can be used without treatment for irrigating crops and for animal drinking water, they are not sealed systems and so it cannot be assumed that they will be contamination free. 3

4 Standards and Regulation Notification to Water Companies Are there any standards? Yes, British Standards have published two documents, BS8515:2009 for rainwater harvesting systems and BS8525-1:2010 for greywater systems. These recently published standards cover the design, installation and maintenance requirements for these water alternative systems and include water quality requirements for the end uses, and are some of the first in Europe. For other sources there are currently no set standards, however the Private Water Supply Regulations cover the use of abstracted water intended for human consumption and food production. They cover water quality requirements and in essence mirror the requirements set out for public drinking water standards. What regulations apply? In addition to the British Standards the requirements of the Water Supply (Water Fittings) Regulations 1999 do apply to properties that have alternative water supplies, (whilst these Regulations apply in England and Wales similar requirements apply in Scotland and Northern Ireland under their own Byelaws and Regulations), and are intended to protect public health and to make sure there is no waste, misuse, undue consumption, contamination or erroneous measurement of public mains water. Do I need to tell the local Water Company about my installation? Normally Approved Plumbers would not have to notify such installations, however some water companies are maintaining records of such systems because of recent problems, so it is worth contacting them to make sure you understand what the local requirements are prior to the installation. 4

5 System Designs This guide covers some of these requirements and gives examples of good practice. In general there are two basic design types for alternative water systems that are commonly used to distribute water to the end use appliances, direct and indirect, and they both have their merits and drawbacks. Direct systems This is where water is pumped directly from a borehole or storage such as the underground tank, direct to the points of use, for example toilets and outside taps. In the event of a failure in any of the sensors, pumps, controls or a power cut there will be no water for the appliances supplied, for example, toilets, outside taps etc. Even the mains water back-up would be of no help, as this normally fills into the low level storage tank or treatment system and needs further pumping. This is the direct system s Achilles heel, however on the positive side it can be easier to install and take up less space as there is no need for any extra plumbing such as high level cisterns etc. an easily accessible manual by-pass valve is installed so it can turn the ball valve on. Whilst this type of system can easily cope with a failure be it electrical or a system fault, it does require some space to locate the high level storage cistern and additional plumbing. This system typically provides low pressure water to the appliances and potentially low flow rates which can be overcome by good design and tap selection etc. It is necessary that whatever alternative source of water has been selected the treatment system used must be able to deliver an appropriate level of water quality for the end use to ensure the users are not exposed to undue risks. British Standards have set health based water quality requirements for the supply of both rainwater and greywater. Indirect systems This is where the alternative water is pumped from the borehole or storage tank up to an intermediate cistern at high level, for example in the roof space, from where it can then feed by gravity to the points of use. By having the mains water backup connected into this cistern it can be made to change over seamlessly in the event of a problem with the system or a power failure. To make sure this will work it is essential to ensure the solenoid valve on the back-up supply is of a type that will open when there is no electrical power to it or, that Typical systems with automatic back-up and manual override. 5

6 Back-Up Water Supply What happens when there is no rain? All rainwater harvesting is reliant on frequent rainfall, and this will vary across the country. Even the areas of the country with the highest rainfall will experience dry periods. So when this happens it is essential to have a mains water back-up supply to keep appliances operating. Greywater systems are reliant on occupiers using baths, showers etc to provide it with the untreated greywater, so this should not be a problem. However should there not be enough untreated greywater to process, or the treatment system fails for some reason, it should be designed so that it is able to continue to operate by providing an alternative supply. Again it will be essential for this to be provided for by a mains water back-up supply. What would happen if there was no mains water back-up supply? If an alternative water system failed or there was no alternative water to supply it, the system would stop working. Users would not be able to flush their toilets or use other appliances, which could potentially lead to public health issues. So it is important that whatever design is chosen at least one toilet must be able to operate normally. It is recommended in larger premises that this is supplied direct from the mains water supply if the design does not incorporate a reliable alternative. Where a back-up water supply is used it should be controlled so that only the minimum amount of water is supplied to the system, particularly if it is being put into a rainwater tank. This will ensure that when it next rains the maximum amount can be captured. Where the back-up water is delivered to below ground storage, consideration should be given to the potential for smells to vent back in to the property. A mechanical waterless trap may be used to prevent this occurring. An example of a mains back-up supply unit. An example of poor installation, with no marking to clearly identify rainwater from mains water. 6

7 Backflow Prevention What sort of risk are alternative waters? Essentially all alternative water supplies must be considered a fluid category 5 risk, that is to say it poses a serious health hazard. Rainwater will contain atmospheric pollution and due to the nature of the surfaces from which rain is collected, means it is also likely to contain faecal, biological or pathogenic contaminants. Similarly greywater and collected wastewater from washing etc., is also likely to contain faecal and pathogenic organisms. Other alternative water supplies from bore holes and rivers are likely to have a wider range of pathogenic organisms and possibly faecal matter and are therefore placed in the same category. What backflow protection is required for the mains water back-up supply? Fluid category 5 protection is required and can only be achieved through the installation of either a Type AA, AB or AD air gap, or through the use of a Type DC pipe interrupter (a device which incorporates an air gap), to separate the mains water supply and the alternative water system. The most common methods are through a Type AA or AB air gap. It must be noted that no mechanical devices are capable of protecting against this level of risk. Therefore no direct or removable cross-connections are allowed. Example of how not to connect water from a bore hole to a mains backup (now disconnected). A cross-connected borehole supply pumped unwholesome water into the public mains supply (now disconnected) because of the difference in supply pressures. To make sure users are always fully protected a permanent protection arrangement or device needs to be used. Reputable system manufacturers provide Category 5 backflow protection in their back-up water system. Clothes washing machines However there is one area where caution is needed, clothes washing machines; these can be supplied from alternative water systems provided they can produce the high quality of treated water needed, and this is becoming more common. Whilst new washing machines typically only come with a cold fill connection, older machines have two feeds. Standard domestic machines do not have the fluid category 5 protection capability that is needed; therefore these must not be connected to both domestic hot/cold water and the alternative water. You can only connect to a washing machine that has suitable backflow protection for fluid category 5 and these are not readily available in the UK. Examples of type AB air gaps. Water supplied by Water Suppliers SgV Type AA, AB or AD air gap to be provided Bore hole supply Spillover level Supply to barn Supply to farm Water not supplied by Water Suppliers or non-potable water Warning pipe CV Mains water supply (now disconnected) Pipe interrupter Not less than 300mm min. SL 7 Outlet

8 Backflow Prevention Dead legs In normal operation the back-up supply should not be needed on a regular basis, and so this low frequency use will offer the opportunity for water to stagnate and should be avoided. Where this is not avoidable, additional backflow protection, such as a single check valve, must be installed at the branch supplying the back-up supply system to protect the drinking water supply. Whole site protection by double check valve. Additional Protection Some Water Undertakers may require additional backflow protection to ensure cross contamination between premises is adequately prevented. It is therefore essential that the local Water Undertaker is consulted as to their requirements prior to installation. Additional protection on the incoming mains supply. Direct system mains water back-up supply Type AA air gap Tundish Water from re-use system to appliances Supply to water re-use system Indirect system mains water back-up supply Type AB air gap weir overflow Fluid Category 5 (Rainwater/greywater) Water from re-use system to appliances Supply from water re-use system 8

9 Pipework Do I need special pipework? Pipes must be made from materials that are suitable for location, temperature range, and the type and quality of the alternative water to be used. This will ensure there are no adverse effects, for example corroding pipework, due to factors such as low ph or other chemical effects. British Standard recommend that a contrasting type or colour of pipework is used to make it easy to identify. Below ground pipework. What should I use? For pipework below ground a contrasting colour for alternative systems must be used. The Water Regulations Advisory Scheme (WRAS) and National Joint Utilities Group (NJUG) recommend that black pipe with green stripes is used, this is detailed in the recently revised WRAS Information and Guidance Note No and meets these requirements. Following these recommendations will ensure that buried pipes can be easily identified during any subsequent excavations. This pipe has recently been introduced into the UK by member companies of the UK Rainwater Harvesting Association (UKRHA) and specialist suppliers, more recently it is appearing in major building merchants as well. What about contaminated land? Where pipework is laid in contaminated ground the pipe must also be of a type that is resilient to any potential contamination that would have a detrimental effect on either the pipe, any fittings to be supplied, or if it permeated into the alternative water supply would make it unsuitable for the intended uses. Example of below ground pipe INFORMATION & GUIDANCE NOTE 1. Introduction Water reuse is an accepted method worldwide for reducing water demand. Rainwater and greywater which is treated wastewater from showers, baths and sinks, are increasingly being collected and reused for applications which do not require wholesome water, such as laundry, WC flushing and garden watering. In addition to these, other sources of water such as blackwater (recycled sewage effluent) and industrial water are being considered for reuse. The purpose of the Water Supply (Water Fittings) Regulations and Scottish Water Byelaws (hereafter referred to as the Regulations) is to prevent waste, misuse, undue consumption, erroneous measurement and most importantly contamination of drinking water. Contamination can occur as a result of backpressure or backsiphonage, both of which can cause contaminants to be drawn back up pipework into the water supply. Reused water, including that which has been treated, is considered to be fluid category 5 (the most dangerous of pollutants posing a serious health hazard) and must not under any circumstances be allowed to come into contact with the wholesome domestic drinking water supplies. To reduce the risk of cross-connection and contamination of the wholesome water supply it is essential that all reused water pipework is both readily distinguishable from other pipework and instantly recognisable wherever it is located, for example inside a property, beneath the street, or on private land. So that accidental or deliberate operation, that could put the wholesome supply at risk, can be avoided all apparatus such as valves and washouts on systems distributing reused water should be suitably marked and significantly different from those normally used on wholesome water distribution networks. New British standards, BS :2010 Greywater systems Part 1: Code of practice and BS 8515:2009 Rainwater harvesting systems April 2011 No ISSUE 2 Marking & Identification of Pipework for Water Reuse Systems Code of practice' have been developed to both ensure compliance with the requirements of the Regulations and the adoption of best practice. This information guidance note (IGN) details the colour coding and marking identification required to ensure that internal pipework and external distribution networks conveying reused water satisfy the requirements of the Regulations and comply with the appropriate British Standard. It also provides information regarding signage for storage cisterns and appliances. In exceptional circumstances local water suppliers may be willing to accept alternatives to the recommendation made in this guidance; however any deviation must be discussed and agreed in advance. 2. Reused water systems Because reused water systems are relatively new to the UK it is important that every effort is made to ensure that all pipework conveying reused water is immediately and easily identifiable to those who come across it. It is therefore essential that, wherever it is located, pipework distributing reused water is both recognisable and distinguishable from that supplying wholesome mains water. The use of contrasting or different pipe materials will make this easier but it will not identify the nature of the contents, and so irrespective of the pipe material used pipes must be marked and labelled to ensure that all pipework conveying unwholesome reused water is distinguishable from other pipework. 3. Notification Water suppliers must be notified in advance and grant consent for the installation of reused water Above ground pipework. What should I use? Current standards do recognise that normal plumbing pipework will be used for alternative water systems, however they do recommend that a contrasting type or colour is used to prevent confusion with the normal plumbing system. Some manufacturers are currently considering the feasibility in making pre-marked pipework for internal use. 9

10 Labelling & Marking Why do I need labels? Fitting labels and marking pipes will ensure users are fully aware of what quality of water is being supplied to their appliances. This will help users take the appropriate precautions to ensure their family do not drink from taps supplied with rainwater/greywater. This contributes to the health and wellbeing not only for current users but for future occupiers, by raising awareness that an alternative water system has been installed. Colour coding pipework Why must you colour code all water alternative pipework? Colour coding of pipework is essential to help prevent any possibility of misconnecting to an alternative water system when carrying out work on the plumbing system. It will also help prevent cross-connections that could lead to contamination of the drinking water supply. Domestic pipes Premises that only have smaller pipes, as in most houses, should use these same principles, but it is acceptable for it to be scaled down to 150mm long. This will ensure a common recognisable marking is used across all properties and pipes can be readily identified. Colours to BS 4800:1989; Green - 12 D 45; Black - 00 E 53 The following methods are recommended: Insulated pipes should be labelled on the outer surface of the insulation, regardless of whether the pipe has been identified prior to insulation, and marking should be designed for the life of the system. Marking can be made at the time of manufacture or labelling attached during installation. Marking should be located along the length of the pipe at not greater than 0.5 metre intervals and at key connection points, but consideration should be given to pipes running through joists or other enclosed areas to ensure they can be readily identified. Commercial/Industrial pipes Large scale water pipelines, e.g. in commercial premises, should be marked using the accepted principles set out in BS1710, Identification of pipelines. The identification colour should be green and black as shown below, identifying it as carrying non-wholesome water from an alternative water system. 10

11 Labelling and Marking Labelling Labelling with tags all taps and valves that supply rainwater or greywater, ensures the users are made aware an alternative water system is present. Point of use appliances such as toilet cisterns, outside taps, and washing machine connections should have point of use labels indicating Not drinking water. Also storage cisterns should be labelled as containing alternative water to make sure there is no confusion as to what is stored. The minimum recommended sizing for outside or hose union taps is 80mm high and for internal use 40mm. Labels should be fitted to isolation valves and key points that indicate supplies of different pressures, qualities, and designated uses. The lettering on these labels should be black on green as above and not less than 5mm in height. 11

12 Maintenance Do these systems need maintenance? Maintenance is vital to make sure maximum benefit can be gained by users, and it is no less true for an alternative water system. A few simple frequent checks may be all that is needed to ensure a system functions at its optimum, as the manufacturer intended. It is critical that users are made aware of this and that it is in their interests to follow the maintenance requirements as specified by the manufacturer. If they fail to do this, it could lead to either system failure or expose them to increased levels of contamination in the water they hope to reuse. To ignore this can be critical. If a customer decides to ignore this or even worse cross-connects to their mains water supply, it can have severe consequences. It is therefore critical these factors are considered during the design stage when selecting the most suitable alternative water system. Summary These alternative water supply systems can offer a way to help save on mains water use, providing they are installed correctly. More and more developers and builders are seeking to install these types of systems in the latest style eco-housing. To ensure that we all can exercise our duties of care, please make sure you follow a few simple checks to guarantee systems are installed properly by: l Notifying water suppliers, where needed, in plenty of time to prevent delays. l Selecting a design that can ensure a constant supply of water is available for critical appliances such as toilets. l Use the correct pipe below ground. l Make sure there are no cross-connections. l Ensuring the backflow protection is of the correct type. l Follow proper labelling and marking requirements. l Follow the British Standard Codes of Practice. l Make sure users are fully conversant with the systems, particularly operation and maintenance requirements. l Water suppliers want to make sure that their customers have a good healthy wholesome drinking water supply, so having a well designed system installed that meets the regulatory requirements helps to serve this purpose. Other references Copies of this guide can be downloaded free from Water Regulations Advisory Scheme: Water Supply (Water Fittings) Regulations quality/water/industry/wsregs99/index.htm BS8515:2009 Rainwater Harvesting Systems Code of Practice. BS8525-1:2010 Greywater Systems Code of Practice. BS1710:1984 Identification of Pipelines and Services. BS4800:1989 Colours for Buildings National Joint Utilities Group Acknowledgements Regulation compliance images reproduced by kind permission of Water Regulations Advisory Scheme (WRAS). Cover image courtesy of RainWaterHarvesting.co.uk. 12