Designs of domestic bathrooms, guidance and advice from www.anglianwater.co.uk Domestic bathroom designs
Contents Introduction... 3 What seems to be the problem?... 3 Understanding the problem... 3 Alternative solutions that can help... 5 Specifications... 5 Turn the bath... 5 Partitions... 5 Hose length... 6 Hose restrainers... 6 Fixed showers... 7 Backflow protection... 7 In summary... 7 Acknowledgements... 7 2
Guidance for the designs of domestic bathrooms Figure 1: Bath shower hose which is long enough to reach the toilet. Introduction This guide aims to assist designers, developers and installers understand the requirements set out in the Water Supply (Water Fittings) Regulations 1999 when designing bathroom layouts to avoid the most common problems. What seems to be the problem? Compact bathroom design is proving popular with designers & house builders as it makes economical use of the available floor space. This design typically place baths in close proximity to toilets and wash hand basins. It is usually found the tap and shower fittings are located close to each other and are frequently unrestrained so they can be used in the bath for personal cleansing as well as a shower. This allows the hose outlet to be placed outside of the bath either in the hand basin or below the rim of the toilet pan (Figure 1). If the water supply failed, backflow could allow contaminated water from the toilet to enter the plumbing system and be drawn off from a tap for drinking or cooking use either within the home or in neighbouring properties. Similar risks arise from flexible shower hoses installed adjacent to WCs for personal cleansing in place of toilet paper (Figure 2). This guidance only covers domestic bathrooms in houses, hotels and other domestic settings such as student accommodation. Bathrooms in other non-domestic settings can be exposed to greater risks and these need to be considered on a case by case basis. Should there be any doubt please contact Anglian Water for further advice. Figure 2: Shower hose provided for personal cleansing. Understanding the problem The risk from backflow at any particular outlet is assessed in terms of fluid categories the least serious being fluid category one (FC1) which is wholesome drinking water supplied by Anglian Water, and the worst being fluid category five (FC5) - fluids containing faecal micro-organisms or pathogens as would occur in toilets and bidets. The zones of risk will depend on what fluids any particular outlet can come into contact with (Figure 3). Depending on which zone an outlet can come into contact with, will define 3
which suitably-rated device can be used to protect the water supply. Figure 3: Zones of backflow risk for a shower handset Where the handset is able to reach into the fluid category 5 zone (Figure 5), the protection needed will require breaking the water pressure through a recognised air gap before it reaches into this zone. In such cases mechanical devices that might otherwise be used are neither appropriate nor acceptable. Fluid category 3 zone Fluid category 5 zone Figure 5: Shower handset moved out of a fluid category 5 zone. Fluid category 1 zone (no protection required) Note 1 Note 2 Spillover level Notes 1. Example of FC3 backflow protection on both hot and cold supplies. 2. Type AUK2 air gap between the shower handset and the spillover level needed for backflow protection. For G1/2 shower hose this needs to be 20mm. This can make it difficult to conform to the Regulations whilst still retaining a good useable shower as the users would expect. Figure 6a: Fluid category 5 configuration for a mains fed hot water system reaching in to the category 5 zone eg combi boiler or unvented cylinder. Where a shower handset can only reach into the fluid category 1 zone, no backflow protection will be needed, but this may limit how it can be used. If the shower handset can reach into the fluid category 3 zone, mechanical devices such as double check valves or self-cancelling diverters, as found on some bath taps, can be effectively used, retaining both functionality and a good shower experience. These types of diverters create an air gap by automatically changing the water flow back to the tap outlet when the flow stops to the shower. Figure 4: Self-cancelling shower diverter shower diverter valve One method is the use of a pipe interrupter (Type DC) see Figure 6a, however whilst this 4
conforms to the Regulations the designer/installer must make sure the shower or toilet handset will operate to meet the needs of the user as this is not guaranteed with this type of configuration. Properties with gravity fed hot and cold water systems can, if configured correctly, have the water supplied using an alternative method than is normally used and would allow the supply to feed shower outlets without risk to the rest of the water supply (Figure 6b). This was initially designed to serve bidets but can be effectively used to serve other types of outlets. Figure 6b: Gravity fed system serving bidet. This arrangement can also be used for shower handsets adjacent to toilets or bidets in the fluid category 5 zone. Alternative solutions that can help In normal bathroom layouts there are several ways to achieve simple and cost effective backflow protection separate to the use of a storage cistern and air gap described above. For this we need to consider the specifications and design of the bathroom layout. Can anything be repositioned, installed or restrained that can move the shower handset out of the highest zones of risk? Specifications Review the specifications and consider installing taps that do not provide the opportunity for a shower handset to reach into high risk zones, or that have backflow protection built in. Turn the bath By considering the design of the bathroom so that the bath taps are at the opposite end of the bath that is nearest to the toilet. This allows the use of a long hose for convenience but can prevent it reaching into the high risk fluid category 5 zone. FC 5 FC 3 The predominance of unvented water heating systems in modern homes means it unusual to be able to use this type arrangement. Even where a roof tank (storage cistern) exists, the air gap usually used would not give the fluid category 5 protection needed, as domestic hot water is usually fed through pipes also serving other outlets at a lower level than the bath combination tap, so the system would not comply. Partitions By installing a fixed shower partition or screen can limit where the shower handset can reach. Fixed shower screen FC 3 FC 5 5
Figure 7: Fixed shower screen in use The restraining ring or clip should be designed and fitted so that it is robust enough not to be easily broken or have the handset removed from it. This can have the same effect as to shortening the hose, whilst still allowing it to be useable. Figure 8: Acceptable shower hose restraints Hose length Using a shorter hose can move the shower handset into a more manageable fluid category zone. A word of caution, do not shorten the hose too much so that it becomes un-useable. Robust pipe clip restraint Shower rail attachment fixed to shower hose FC 5 FC 3 Pipe restraining clip Figure 9: Unacceptable shower hose restraints Hose restrainers Anglian Water with other water suppliers acknowledge that restraining shower hoses, either by an attachment or ring, is an acceptable alternative to recognised backflow prevention devices. Restrained by tape Zip tie restraint FC 5 FC 3 Jubilee clip restraint 6
Figure 10: Correctly restrained shower hose Installing a double check valve to the shower hose connection on the bath combination tap or shower valve (Figure 11). Figure 11: Double check valve installed on to shower hose connection double check valve It is recognised that from time to time shower hoses will require replacing and the use of tamper proof screws are not required. It is important that any such hose restraining fittings are approved by Anglian Water or the water industry, to ensure they are fit for purpose. It is essential that they are installed and used in accordance with the manufacturer s instructions to assure effective and reliable backflow prevention. Fixed showers Consider the use of fixed showerhead as these, if installed appropriately, can be fitted in the fluid category 1 zone therefore no additional backflow protection will be required. Backflow protection Once the fluid category zone has been determined appropriate backflow prevention must be installed in accordance with the Regulations. For domestic premises, where the shower hose can only reach into the fluid category 3 zone, ie cannot reach the toilet (Figure 3) but can be left below the rim of the bath or wash hand basin, the bath combination tap or shower valve must be protected by a fluid category 3 three device. This can be achieved by: Installing a bath/shower combination tap with a self cancelling flow diverter (Figure 4), or Installing a double check valve (type of nonreturn valve) to both the hot and cold water supplies to the tap or shower valve, or Please note: Bath taps with manual lever diverters do not normally have inbuilt protection and will need extra backflow protection fitted externally. In summary By following this guidance will ensure that designers will have considered the needs of users in maintaining usability of shower handsets within the limits of the Regulations. Users, owners and occupiers will have the confidence they will be able to use their showers as they expect to and remain within legal requirements. Acknowledgements Water Regulations Guide images reproduced by kind permission of Water Regulations Advisory Service (WRAS) www.wras.co.uk 7