PLUMBING SYSTEMS


of the pipe, and that the occupier will experience discoloured turquoise or blue/ green water. This phenomenon is particularly prevalent in areas where the water is particularly ‘soft’, as the water will be from a peat source, for example moorland, and the water will tend to be on the acid side of neutral. If ‘blue water’ is being experienced by users, there is a process that DRLC has patented and successfully used to help stop this form of corrosion in potable water supplies.


Pinhole pitting caused by Microbiological Influenced Corrosion (MIC) in a hospital’s potable water supply.


service. The problems copper pipe corrosion causes may manifest themselves in leaks caused by pin hole corrosion and high dissolved copper levels also known as ‘blue water’. However, this low level of copper usually leaves a green/blue/ turquoise stain on taps, washhand basins, and showers etc. This water is still generally safe to drink after flushing for over 10 seconds or so, but a high level of copper in your drinking water will leave a metallic or bitter taste. This water may not be safe to drink, and you should contact your drinking water provider or have the water professionally tested. Water which has been turned blue by dissolved copper is generally not drinkable, with the maximum limit of dissolved copper being 2 mg Cu/litre.


Problems are more likely to occur in large, complex systems, such as those found in hospitals, hotels, and large office buildings, where pipe runs are long, and the hot water is distributed through a recirculating system. Problems with copper corrosion are rarely encountered in normal residential houses, unless commissioning of the systems has resulted in water stagnation.


High rates of copper corrosion Cuprosolvency describes high general corrosion rates of copper, with the release of elevated dissolved copper ions in water, and ‘blue water’ is the term used to describe discolouration of the water often seen against a white background, as found in sanitary fittings. This can occur where newly installed completed copper pipework is unlikely to be used within a few days after pressure testing, and the water is left within the pipework. One way to prevent this happening is to drain down the water system to prevent water stagnation in the pipe. If this is not possible, the system should be flushed twice a week. The guidance published by WRAS on commissioning, ‘Commissioning Plumbing Systems’, can be found at www.tinyurl.com/17jabjzo


If these techniques are not followed, then it is possible that Copper Oxides/ Cupric oxide will build up on the inside


Problems in large institutional buildings


In large institutional buildings, especially in soft water areas where organic matter could be present in the water supply, copper pipe corrosion problems in the form of localised pitting or ‘pinholes’ could be experienced. An electron microscope analysis of corrosion in pipework from a large teaching hospital in the north of England, which had experienced pinhole leakage after being installed for 7-8 years, found microbes resembling actinobacteria in the pits stuck between the crystallographic planes of the corroded copper grains. This form of corrosion can manifest itself as a stalactite consisting of microbiological growth from the upper inner surface of the pipe, which pierces the underside of the copper pipe, causing localised pinhole rupture of the underside


David Livingstone


David Livingstone B.Eng (Hons), C.Eng, FIHEEM, MCIBSE, MBCS, is an Authorising Engineer and consultant engineer, holds Chartered Engineer status, and is managing director of DRLC, Consulting Engineers. DRLC works mainly with NHS Trusts, supplying technical expertise and Authorising Engineers in the areas of Ventilation, Fire Safety, and Pressure Systems. The company, which has grown over the past five years, also provides Design Review services for Critical Ventilation and Premises Assurance Model (PAM) assessments, and CQC assurance inspections to NHS Trusts.


Having begun his engineering career as an apprentice Marine Engineer in the


Merchant Navy, David Livingstone worked his way up to achieving qualifications as a Second Engineer and obtaining his steam ticket. He worked on a variety of ocean-going ships, including container carriers and oil tankers. On coming shoreside he secured his first post in the NHS as an engineer in the Estates Department of the Northern General Hospital in Sheffield, one of the largest hospital sites in England. Looking for a variety of engineering experience, he moved from NHS estates maintenance to delivering engineering projects for Sheffield Hallam University, and then on to becoming head of Estates for another large NHS Trust – Nottingham University Trust, which at the time comprised the Nottingham City Hospital and Queen’s Medical Centre. His career inside the NHS ended with a role as director of Estates and Facilities. He then launched DRLC Ltd in 2016, with a view to providing Authorising Engineering Services to healthcare providers.


July 2021 Health Estate Journal 39


of the pipe. As this form of pitting has been widely experienced in Scotland, NHS Scotland has changed its Heath Technical Specification CO1 - Mechanical Specifications to address this problem. NHS Scotland recommends that in areas with soft water, and / or where high levels of organic sediment are found, filtration to remove organic matter should be considered, in addition to using alternative materials to copper for the water supply pipework. These alternative materials include austenitic stainless steels, polyvinyl-chloride (PVC) plastics, or polybutylene or cross-linked polyethylene (PE-X).


In conclusion


Using copper to transfer drinking water is a long-established, and usually problem- free, way of delivering drinking water. On rare occasions the solder used to connect lengths of copper pipe can start to dissolve, causing contamination of the water with metals not considered healthy in high concentrations. In other circumstances, the inside of the copper pipe can develop cuprosolvency, where the copper ions enter the drinking water, turning the water a blue colour, and making it unsafe to drink. There is also the possibility of bacteria infecting the copper pipe, and causing plaques of corrosion, which eventually cause pinhole pitting in the wall of the pipe.


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©Dr Phil Munn/Midland Corrosion Services Ltd


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