24
feature
drainage, plumbing & water saving solutions
management of dead legs and blind ends in water systems
Roy Sullivan, Senior Consultant at the Water Hygiene Centre, takes a look at the differences between dead legs and blind ends and shares some practical tips for managing them...
There is a requirement for all building managers to ensure the safety of the public and employees so far as reasonably practicable. This requirement is set out in the Health and Safety at Work Act 1974, The Management of Health and Safety Regulations 1999, Control of Substances Hazardous to Health (COSHH) 2002, the HSE’s ACoP L8: “Legionnaires’ disease, the control of legionella bacteria in water systems”, the associated HSG274 Technical Guidance Part 2: “The control of legionella bacteria in hot and cold water systems” 2014 and the Department of Health’s HTM 04-01 “Safe Water in Healthcare Premises” Parts A, B and C, 2016.
What are dead legs and blind ends? The Health Technical Memorandum 04-01 Part B defines a dead leg as a length of pipework leading to a fitting through which water only passes infrequently when there is a draw-off from a fitting, creating potential stagnation. HTM 04-01 Part A Section 12.5 sets out guidance that pipe branches should be designed to avoid stagnation. As far as practical, the maximum length of any pipework between a terminal device and a recirculating system or a cold-water distribution mains should be kept to a minimum; generally, the complete length of the spur should not exceed 3m. The length is measured from the centre line of the circulation pipework to the point of discharge along the centre line of the pipework. These pipes should be insulated. A blind end is defined in HSG274 Part 2 as a length of pipework that is closed at one end through which no water passes. For example, where a wash hand basin in a room has been removed, allowing the room to be used as a store or office, the basin supply pipework may be capped off, leaving lengths
of pipework containing stagnant water and creating blind ends on the hot and cold water services. Both blind ends and dead legs increase the risk of biofilm
formation and create the right conditions for Legionella, Pseudomonas aeruginosa, and other waterborne pathogens to proliferate. These waterborne pathogens may then leach back into the parent supply and contaminate the system, thereby increasing the health risk to anyone using the water system. Biofilm is defined as a complex layer of microorganisms that have attached and grown on a surface. This form of growth provides a niche environment for a wide range of microorganisms to interact, where the secretion of exopolysaccharides by bacteria forms an extracellular matrix that protects both bacteria and other unicellular organisms, such as amoebae and flagellates. The internal surfaces of pipework, water tanks, water outlets, shower heads and hoses are a few examples where biofilm can form.
How can they be managed? Where water is allowed to stagnate, there is a risk of contamination. The key elements of managing the pipework distribution system are to keep the system clean, keep the water flowing, and keep the hot water hot and cold water cold. In addition, the following points should also be considered;
1. Ensure the Legionella risk assessment, schematic drawings, and as-fitted drawings are up to date and reviewed.
Continued on page 26...
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
