WATER SYSTEM MANAGEMENT
takes account of the upstream pressure varying the hole size. This gives greater control, and offers consistent flow delivery over a wider range of pressures. Tap aerators are fitted to the outlet spout of the tap. They typically contain a flow regulator within the cartridge, but then have an additional element which draws in and mixes air in with the water flow. The air gives a visible increase to the volume of the flow. This also ‘softens’ the flow, which reduces splashing when the water makes contact with the sink or basin. As these are fitted to the ends of the tap, it is easier to select the right flow for each tap and to maintain it.
Impacts on systems When designing new buildings it is much easier to incorporate these technologies. However, retrofitting them into an existing system may have unintended impacts, so requires careful consideration. This applies not only to the water supply system, but also to other connected services such as the drainage, which we are not able to go into in this article. So, what do all these savings mean for the system itself? Firstly, reducing point of use flow rates or usage has the knock-on effect of slowing the speed that water flows through the pipes supplying them. This can also increase the time that water stays in the pipe. In the aforementioned example the residence time can be two to three times longer. Longer residence times can have a number of significant impacts. Firstly the residual disinfectant, in public water supplies to limit microorganism growth, dissipates over time. Long residence times mean that its protective effect will be lost. Secondly, water has much more time to absorb heat from the pipe’s environment, increasing its temperature. This can be problematic if the temperature gets too high. Temperatures between 20 °C and 45 °C give microorganisms the ideal thermal conditions for them to thrive and multiply. This is the reason why there are controls, set out in guidance such as HTM 04-01, and the Health and Safety Executive’s ACoP (Approved Code of Practice and guidance) L8, Legionnaires’ disease. The control of legionella bacteria in water systems, which rightly require cold water to be kept below 20 °C. However, these are not the only problems. The speed at which water travels
through pipes can help limit biofilm growth within pipes and fittings. It does not need to be a continuous flow, but does need to be sufficiently high on a frequent basis
‘‘
A selection of devices: tap aerators (a and b); an inline flow regulator (c); a flow straightener (d), and a flow insert (e).
so that it turns over the whole volume of the pipe. Good system design – including the selection of pipe sizes – can prevent stagnation, and maintain water safety within plumbing systems.
Common mistakes and concerns There are a few common mistakes made in striving to save water – for example, using isolation valves to reduce flow by partially closing them. This is a less than optimal method, particularly for the quarter-turn style valves. It creates high speed flows across the face and seating of the valve, which can result in high wear, and may not fully shut off when you need it to. Without reducing pipe sizes, residence times can increase, allowing stagnation and potential biofilm growth. Reducing flow rates can also affect the balance within return loops, which can affect the way they operate. When planning to introduce water-
saving technologies it is imperative that the whole water system is fully considered. Combining water saving measures across multiple outlets can mean a substantial change to flow patterns, which will be compounded when applied across a larger building’s system. This may mean reconfiguring pipe routes, pipe size reduction, or rebalancing to optimise flows, not only on cold supplies, but the hot water system as well. Sufficient throughput needs to be maintained throughout all legs to ensure
Surprisingly, not all products sold have been appropriately tested, so it is worth checking that products have been tested to conform with the Water Fittings Regulations
that stagnation and heat gain are limited. Designers also need to take care if they remove storage cisterns, which have backflow protection integrated. A better alternative may be to reduce the size of the cistern, thus achieving sufficient turnover.
Risks with aerators In areas where there is a high level of infection control, aerators on the end of taps may not be an appropriate water- saving method, as they can retain water within them. Additionally, these types of outlets need to be easily disinfected, which may require the outlet fittings to be readily removed. In these circumstances inline flow control may provide the better option. However, anything which places a restriction, or has the potential to trap debris, needs to be readily accessible. Choose designs that enable easy removal for maintenance, and the flexibility to alter the flow rate using replacement cartridges.
Installer competence and compliant fittings As well as protecting the quality of drinking water, the Water Fittings Regulations are designed to prevent the ‘waste and undue consumption of water’. These regulations also govern the design, installation, operation, and maintenance, of plumbing systems, water fittings, and appliances which use water. Plumbing products and appliances supplied by wholesome water from public supply must be of an appropriate quality and standard. It is only when fittings are properly tested that manufacturers and suppliers can be certain that they comply. As you might expect, conformity standards include tests
March 2023 Health Estate Journal 25
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
