PLUMBING SYSTEMS
Copper corrosion issues – and how to tackle them
David Livingstone, a Chartered Engineer, Authorising Engineer, and corrosion professional, who is managing director of DRLC, Consulting Engineers, examines the issue of corrosion in plumbing systems, with a particular focus on the potential problems that may be encountered with corrosion within copper pipework.
Copper has been used for over 4,000 years as a material to transport clean potable water. The Egyptians in 2000 BC used copper to convey water. They were skilled coppersmiths, and used the water to provide drinking water, water for the bathing rituals in their temples, and also to irrigate their fields. Although the Romans used stone aqueducts, lined with cement, to carry water from their reservoirs into cities, the final distribution was carried out using lead pipes. In 27 BC a Roman architect and engineer, Marcus Vitruvius, in his book De architectura, pointed out the dangers to health of using lead piping to transport water. High levels of dissolved lead in drinking water can cause brain abnormalities in growing children, and a number of wasting diseases in adults. The Romans, who were known to be excellent engineers, took this seriously, and began constructing new water pipes in copper and bronze. Copper is strong and malleable, and thus easy to work with, and also has antimicrobial properties. The Egyptians, Greeks, Romans, and Aztecs used copper compounds for the treatment of disease and good hygiene. Egyptians used copper as a sterilisation agent for drinking water and to treat wounds.
An extensive network
Fast forward to the present day – and water from reservoirs is transported in pipes or tunnels, commonly referred to as water mains, and these distribute water around the network. From these network distribution pipes there are communication pipes, which carry the water between the water main and the boundary of properties. However, hospitals may have their own water mains, and generally have two main supplies for resilience. These pipes are made from a variety of materials – including cast iron, high density polyethylene, and, in some instances, austenitic stainless steel. The final leg of the journey from reservoir to the point of use is almost exclusively accomplished using copper pipe.
Types of water mains
At various points in the past 50 years there have been several different materials which have been used to make water mains. Among the most common are: n Blue MDPE polyethylene pipe – more commonly known as ‘blue poly’, is the current industry standard material that is used for water mains in the UK. It offers high levels of flexibility without compromising its strength. Medium
density polyethylene pipes have a disadvantage when used underground; near petrol stations they can become contaminated with petrol, which can permeate through the plastic pipe. Similarly, pipes running under agricultural land can also become contaminated with nitrate insecticides, which have been absorbed by the polyethylene pipe.
n Lead pipe was most commonly used in the past to make water mains. Ageing lead pipes are known to deteriorate over time, reducing the structural integrity of the pipe, and are known to fur up internally. This furring up will reduce water pressure, and hence water flow rates. Lead has been banned and is potentially harmful. The leaflet, ‘Lead in drinking water’ from the Drinking Water Inspectorate (DWI) (see
www.tinyurl.com/j5kfgea4), explains how lead can get into water, and what you can do to safeguard health.
n Black alkathene – Much like ‘blue poly’, black alkathene is a highly flexible plastic pipe. It was commonly used in the 1980s to 1990s, but has been replaced by blue poly pipe more recently. The fittings on black alkathene often developed leaks, and that is one reason why blue poly replaced black alkathene.
The More Hall Reservoir, Ewden Valley, Stocksbridge, in Yorkshire.
n Cast iron – the majority of water piping installed in the 20th century was cast or ductile iron, which was expected to provide a life of 50 to 100 years of trouble-free service. Unfortunately, these pipes are susceptible to corrosion and subsequent breakage. Factors contributing to corrosion include soil conditions, connection to dissimilar metals which allows galvanic corrosion to take place, and road salt. Older, cast iron pipes are prone to lose their strength and ductility, causing the pipe to become brittle and fail. Ductile iron pipe, introduced to water systems in the 1950s, and still in use today, was intended to offer better quality than cast iron. However, the pipe had a thinner wall thickness, which makes it vulnerable to pitting corrosion attack.
July 2021 Health Estate Journal 37
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