buildings Reginald Brown Tap Drinking Domestic Mains Wholesome - PowerPoint PPT Presentation

Domestic water in commercial buildings Reginald Brown

Tap Drinking Domestic Mains Wholesome Fresh Sanitary Potable 2 The built environment experts

Mains water myths Sterile • Aerobic bacteria 3- 34 cfu/ml as supplied to BSRIA - could be much higher out of the tap Pure • 140 Ca, 6 Mg, 60 SO 4 , 58 Cl, 36 NO 3 mg/l • TDS ~ 450 mg/l Harmless • Domestic water leaks probably cause more damage in buildings than heating and cooling system leaks. Insurance claims run into million of pounds each year. 3 The built environment experts

Water quality reports Available free from water companies web sites 4 The built environment experts

Domestic water system issues  Corrosion and erosion – Pipes needing replacement in less than 2 years  Colonisation by bacteria and other microbes – Pseudomonas – Legionella – Protozoa, filamentous fungi etc  Joint failures – Catastrophic release of water Unfortunately no time for joint failures today! 5 The built environment experts

Corrosion 6 The built environment experts

Corrosion risks  Most domestic water systems use copper tube  Copper pipework in new or refurbished buildings is at high risk of pitting leading to pinhole corrosion from: – microbiologically influenced corrosion (MIC) – disinfectant residues – flux residues – scale deposits If the water is allowed to stagnate !!! 7 The built environment experts

Legionella guidance The draft of HSG 274 Part 2 The control of legionella bacteria in hot and cold water systems has a recommendation to use gas pressure testing to avoid a prolonged stagnation period prior to commissioning. If accepted by industry this may reduce the risk of some causes of pitting. The draft also suggests that weekly flushing of filled systems should be implemented to reduce stagnation and maintain the level of chlorine from the incoming supply. BSRIA experience is that weekly flushing unlikely sustain the mains chlorine level or be sufficient for the control of pitting corrosion. 8 The built environment experts

Corrosion feature on outside 9 The built environment experts

Typical nodule in base of pipe 10 The built environment experts

Malachite and azurite crystals capping corrosion pit 11 The built environment experts

Section of perforated pit Malachite & Azurite (mineral forms of basic copper (II) carbonate) Cuprite (a mineral form of copper (I) oxide) 12 The built environment experts

Two sections from the same pipe 13 The built environment experts

Pitting features 14 The built environment experts

Linear spots 15 The built environment experts

Micrograph of spots 16 The built environment experts

Why black? 17 The built environment experts

Basic SEM 18 The built environment experts

Scanning electron microscope (SEM) micrograph 19 The built environment experts

SEM Energy dispersive x-ray spectroscopy (SEM-EDS) 20 The built environment experts

Elemental maps around the perforation Copper Oxygen Phosphorous Chlorine 21 The built environment experts

Progress of corrosion pinholes Surface dirt Carbon Chlorination Flux Biofilm and debris film residue residue Initiation of corrosion cell Stagnation Pitting Perforation 22 The built environment experts

Microbiologically influenced corrosion 23 The built environment experts

Typical result of microbiological corrosion 24 The built environment experts

Electron micrographs of microbiological corrosion features Underside of nodule Pitted surface 25 The built environment experts

Assessing the cause of pitting  It is more productive to look at pits that are still forming than a hole  Well developed pits have similar composition irrespective of the original cause – usually rich in chlorine  Assessment of the root cause of pitting depends on looking at the general surface of the pipe (visually and by composition of scale) as well documentary evidence regarding the history of the system  In-pipe endoscopy can help to determine the extent of the problem 26 The built environment experts

Incidence of pinholes  Most corrosion pin-holes occur in cold water pipes – Most commercial building systems use pumped hot water circulation which avoids stagnation – only the final connection to the tap will be subject to stagnation  All erosion pin-holes occurs in hot water pipes on the return – The root cause is excessive flow velocity in poorly balanced systems 27 The built environment experts

Endosopy in 15 mm copper pipe using 6mm camera 28 The built environment experts

Erosion 29 The built environment experts

Turbulent erosion 30 The built environment experts

Turbulent erosion 31 The built environment experts

Erosion of scale 32 The built environment experts

Cavitation 33 The built environment experts

Bacteria 34 The built environment experts

Bacteria and other microbes  Microbiologically influenced corrosion – Sulphate reducing bacteria – Pseudomonads  Pathogenic bacteria – Pseudomonas aeruginosa – Legionella 35 The built environment experts

Endoscopy of 15 mm hot pipe 36 The built environment experts

The source of the video 37 The built environment experts

Draft legionella guidance  A lot more background information on water systems but the principles of legionella control have not changed  Recommendation on avoidance of stagnation is generally welcomed as mentioned earlier but some concerns on the safety and effectiveness of gas pressure testing  Some concern also over the inclusion of chlorine as a candidate for continuous supplementary disinfection as it is not very effective against legionella and potentially detrimental to some system materials 38 The built environment experts

Differences in risk assessment between legionella and pseudomonas aeruginosa  Legionella – Enters the system through the water supply – Colonises parts of the system with favourable temperature and nutrients – Risk assessment looks at the design, construction and operation of the water system  Pseudomonas aeruginosa – Enters the system from the outlets – Colonises the outlets and fittings – Risk assessment looks at the way the outlets are used and maintained i.e. people factors – Specialist guidance in HTM 04-01: Addendum - Pseudomonas aeruginosa – advice for augmented care units 39 The built environment experts

Thank you!  The new Illustrated Guide to Domestic Water Services will be published later this year and available as a free download to BSRIA members.  BSRIA is also involved in the drafting of BS 8554 Code of practice for the sampling and monitoring of hot and cold water services in buildings also to be published later this year. Reginald.Brown@bsria.co.uk 40 The built environment experts