FLUID CONTROL SOLUTIONS Water’s flowing in the wrong direction
Understanding backflow There are two main types of back flow: Back pressure: which happens when the pressure in non-potable (potentially contaminated) system exceeds the mains water supply pressure. Back siphonage: typically caused when there’s a sudden drop in mains water pressure; when an upstream pipe bursts, for example, creating a vacuum effect that draws water backwards into the supply line.
P
In the wake of recently updated industry guidance that stipulates reduced pressure zone (RPZ) valves must be tested by competent testers, Steve Mulvany from LCL Awards looks at backflow, the potential issues it causes and how to prevent it.
reventing backflow – when the normal direction of water flow is reversed due to changes in pressure – is essential to ensuring contaminated water cannot enter the clean mains water supply. In buildings with a high public footfall, such as hotels, schools and hospitals, contaminated water also presents a risk to health, particularly where vulnerable people may be exposed.
If backflow occurs and contaminated water enters the mains, this risk becomes more widespread and contravenes Water Regulations, leaving facilities managers and building owners open to legal action. Industries including healthcare, food processing, manufacturing and construction sectors are at the highest risk.
Backflow water is categorised into five fluid types:
Fluid Category 1: Clean or ‘wholesome’ water that poses little risk. Fluid Category 2: Changes in appearance, temperature or taste, but no health risk. Fluid Category 3: Containing substances of low toxicity, which pose a slight health hazard, like ethylene glycol or copper sulphate.
Fluid Category 4: The presence of chemicals, pesticides, or carcinogens. In the HVAC sector, this type of water is commonly found in closed heating and cooling systems which include inhibitors, biocides and sludge. This is the level at which the building services sector most commonly concerns itself with. Fluid Category 5: Serious health hazard due to the concentration of pathogenic organisms, radioactive or very toxic substances, like faecal material or other human or animal waste.
Reducing the risk of backflow To reduce the risk of backflow issues, the
following essentials must be understood by building managers and their maintenance teams: 1. Fluid categories: Familiarity with the categories of water contamination (from 1 to 5) is essential in selecting the right backflow prevention devices: Air gaps: The most effective method which involves a physical separation between the water outlet and the receiving vessel. Double Check Valves (DCV): Used in lower- risk situations, ensuring water only flows in one direction. Reduced Pressure Zone (RPZ) Valves: Provide advanced protection against back siphonage and back pressure. Vacuum Breakers: Prevents siphonage in hose and faucet connections.
2. Risk-assess each installation: Every building and water system is different. Conducting a risk assessment will help identify where the greatest vulnerabilities lie. Signs that backflow prevention methods are failing include low water pressure, leaks, discoloured water, unusual odours, and valve malfunctions.
1. Maintain and test annually: RPZ valves must be tested for compliance at least annually by an approved tester. Poorly maintained valves can become a weak link in the system therefore regular maintenance is essential. 2. Work with local water undertaker: RPZ valves require notification and approval before installation. Liaise with the local water undertaker early in the process. 3. Keep documentation up to date: Inspection records, test certificates, and
installation documents are a key part of compliance. Ensure these are accurate and readily available.
RPZ valves explained
RPZ valves comprise an arrangement of two- non return valves with a pressure-monitored zone in-between. If either valve fails, the central relief zone opens to discharge water safely rather than allowing it flow backward into the water supply.
Due to complexity and risks associated with these devices, RPZ vales must only be installed, commissioned, tested and maintained by suitably qualified individuals and unlike some backflow prevention arrangements, RPZ valves are not fit and forget. Annual testing is essential in accordance with the Approved Installation Method (AIM). Since January 2025, installers, commissioner and testers of RPZ valves must hold a suitable industry recognised qualification, which must be re-assessed every five years.
RPZ valve testers who qualified after November 2021 should revalidate their qualification every five years from the certification date. Those who completed training prior to December 2020 must revalidate their qualification by the end of 2026. There is also a new minimum specification for RPZ valve testing equipment. RPZ valve testers have until June 2026 to make ensure their test equipment complies with the new requirements.
www.waterregsuk.co.uk/information/ publications/guidance-booklets/
Brilliant. British.
A2L Compliant Products Now Available
CO2 Evaporators Condensers HFC Evaporators Water Coils CWC, LPHW, Fan Coils Chillers, Flatbed, V-block, U & C shape coils Marine grade, heavy duty equipment Bespoke, bulk and specialist Office POD Cooling Systems
Beehive Coils hp BSEE
Apr24.indd 1 22 BUILDING SERVICES & ENVIRONMENTAL ENGINEER MAY 2025
t: 01638 664134 w:
beehivecoils.co.uk e:
sales@beehivecoils.co.uk Read the latest at:
www.bsee.co.uk 19/3/24 16:10
MADE IN THE UK
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
