Water services in sustainable refurbishment

Transcription

1 Water services in sustainable refurbishment Reginald Brown 1

2 Water stress 2

3 Water efficient fittings and appliances 3

4 Water saving fittings Grey water toilet Waterless urinal Source: Caroma Source: Falcon 4

5 Objectives of sustainable refurbishment of water systems Provide a safe, secure and affordable water supply at the point of use Reduce the impact of water use on the environment Reduce water abstraction Reduce wastewater discharge Reduce inputs of energy and chemicals to the water cycle Comply with regulatory requirements 5

6 Spectrum of refurbishment 6

7 Change of use - prison to luxury hotel Malmaison Oxford Hotel 7

8 Major redevelopment St Pancras Renaissance Hotel 8

9 Typical reasons for pipework replacement Wrong route Wrong size Wrong type Worn out History of maintenance problems Can t achieve water quality requirements Can t achieve legionella control Pipework does not serve required locations Too large or small (pipe size and/or storage volume) for estimated consumption Inappropriate operational characteristics (pressure, temperature etc.) Life expired Leakage, corrosion, scaling etc Dissolved metals, bacteria etc Hot and cold water temperatures, dead legs (and any of the above) 9

10 Pipework condition assessment External visual condition under insulation Evidence of leakage and corrosion Endoscopy Useful for assessing scale, debris and biofilm if you can get access Ultrasonic thickness Possible use for steel pipes Physical removal and inspection of samples Disruptive but provides unequivocal evidence of pipework condition Water quality TVC, pseudomonas, metals, suspended solids 10

11 Corrosion and scale Corrosion in galvanised steel pipe Long term scale build-up in copper tube 11

12 Scale and corrosion Tap restrictor blocked with scale particles 12

13 Erosion in hot water returns 13

14 Poor workmanship Badly brazed copper tube Solder flux residue 14

15 Installation debris Plumbing compound residues 16

16 Phenolic foam Multiple leakage sites on 42 mm copper tube revealed by pressure test Polished section of pipe wall at leak site shows formicary corrosion 17

17 Pitting in stainless steel Pinhole leak in connection to hot water cylinder Micrograph of internal surface 18

18 Pitting in copper 19

19 Stress corrosion cracking 20

20 Design methodology Start at each outlet and work back to the supply Terminal fittings Intermediate fittings including valves Distribution pipework Hot water generator Cold water storage Metering Consider flows, pressures, temperatures and potential water quality constraints at each node in the distribution system Assess the suitability of the existing system against the new requirement 21

21 Is newer better? Heavy grade galvanised steel pipework on cold water service can last over 70 years Galvanising does not prevent internal corrosion on hot water pipe which may also be subject to scaling Copper pipe has long life depending on operating conditions (water quality, velocity, scaling etc) Stainless steel is not immune to corrosion Plastics may be viable commercial buildings subject to periodic refurbishment Even if pipework is retained tanks, valves and fittings may need to be replaced 22

22 Water regulations Water supplied to occupants has to meet current regulations where relevant: The Water Supply (Water Quality) Regulations 2016 The Private Water Supplies (England) Regulations 2016 Legionella risks (COSHH and HSG 274 Part 2) Any repairs or modifications to pipework systems have to comply with: The Water Supply (Water Fittings) Regulations

23 Building Regulations Refurbishments involving extensions or material change of use have to comply with Building Regulations Part G All unvented hot water systems have to comply with Building Regulation G3 24

24 Water fitting reliability issues Water quality Water pressure Low flush WC No concerns No concerns Low flow taps Thermostatic mixing valve Pressure reducing valve Non-return and check valves POU hot or chilled water Kitchen appliances Scaling can cause screen blockage Sensitive to particles and scaling Sensitive to particles and scaling particularly when used on hot water Sensitive to installation debris and particles Poor water quality can result in frequent filter changes Minimum pressure requirement Balanced pressure requirement Under-sized valves can lead to noise problems No concerns Minimum pressure requirement 25

25 Water fittings 26

26 Water fitting reliability issues Unvented hot water retrofit Combi boiler retrofit HIU retrofit Water softener Cold water booster Water quality No concerns DHW heat exchanger scaling in hard water DHW heat exchanger scaling in hard water Excessive softening causes downstream corrosion issues Hard water can result in frequent pump deal replacement Water pressure Minimum pressure requirement Minimum pressure requirement Minimum pressure requirement Minimum pressure requirement Minimum pressure requirement to avoid cavitation unless designed for break tank 27

27 Legionella issues in refurbishment Heat gain to cold water pipes relocated into corridors Proliferation of low water use outlets Excessive pipe diameter (for reduced demand) results in low water velocity Excessive storage volume in tanks (relative to reduced demand) results in low turnover Corrosion, scale and biofilm in retained pipework may increase the risk of legionella growth and reduce the effectiveness of supplementary disinfection 28

28 Rain water systems The simplest form of water recycling Underground storage Minimal treatment Separate distribution pipework Positive contribution to SUDS by buffering rainfall events 29

29 Integrated water use BS :2010 Greywater systems. Code of practice BS 8515:2009+A1:2013 Rainwater harvesting systems. Code of practice 30

30 Water reuse at Greenwich 1999/

31 Extreme recycling Old Ford Water Recycling Plant for 2012 Olympics 32

32 Old Ford Water Recycling Plant Wastewater (636 m 3 /day) Taken from the Northern Outfall Sewer, the main sewer collecting crude wastewater from North East London and transporting it to Beckton Sewage Treatment Works Treatment Septic tanks and membrane bioreactor (MBR) with additional activated carbon and hypochlorite disinfection stages Treated water (574 m 3 /day) distributed though a 3.65 km non-potable distribution network within the Olympic park Used for irrigation and toilet flushing 33

33 2012 Olympics non-potable water use Source:The Old Ford Water Recycling Plant and non-potable water distribution network (london2012.com/learninglegacy) 34

34 Sustainable water solution Hockerton Housing Project 35

35 Closing slide 36