Making noise about heavy metal
The European Drinking Water Directive sets new legal requirements for lead in drinking water. Barny Parks of pipe and fitting manufacturer SANHA explains how contractors can ensure they comply with the legislation
IF THERE IS one New Year's resolution you need to keep, then it is to comply with the requirements of the new European Drinking Water Directive.
The directive, DWD98/83/EG to give it its official title, came into force on Christmas Day. It sets new requirements for the microbiological and chemical water quality of drinking water. Importantly, the directive includes a reduction of 60 per cent on the current 25g/litre limit for the lead content of drinking water.
Contractors have a mandatory responsibility to adhere to all relevant legislation. Achieving the new lower 10g/litre limit for permissible lead levels could pose a significant challenge for them, particularly since up to half the allowable concentration of lead is permitted to be present in mains water supplied by the water utility.
In the UK it is rare for lead to occur naturally in ground water so, if it is present in the water supply, it is most likely to have come from existing lead service pipes which were installed when it was common for lead to be used to fabricate small water pipes and mains.
Lead ceased to be used in drinking water systems in the 1970s following concerns that the metal could affect the mental development of children. However, lead pipes are often still present in properties built prior to the ban, often as the connection to the water main where the house has not been refurbished.
Where lead pipes do remain, lead can continue to leach from the pipe walls into the water supply. Leaching is less of a problem in hard water areas because of the scale that forms inside the pipes helping slow the dissolution of lead. In soft water areas, water companies often treat water by adding orthophosphate to reduce the problem. However, even when the chemical is present, particles of lead can still build up in older pipes and appear intermittently in tap water.
The illegal use of lead-based solder is another source of lead in drinking water. Fittings assembled using lead-solder are sold for use on closed circuit central heating systems. Occasionally, these fittings find their way into drinking water systems when householders carry out a DIY installation or when an unqualified plumber wrongly installs lead solder fittings in a system.
The lower levels of lead permissible under revisions to the Drinking Water Directive means less familiar sources of lead including the use of lead in the manufacture of plumbing fittings also need to be considered alongside these established sources of lead.
Lead is often added to brass and other alloys in concentrations of around two per cent to enhance its machinability. The melting point of lead is lower than that of an alloy's other constituents however, which means that it tends to migrate towards the surface of the metal where it can more easily leach into the water supply. In addition, machining and cutting operations can also smear lead over the surface of the alloy.
As a consequence of these factors significant amounts of lead can leach into a drinking water supply from low-lead content alloys for a considerable time after installation. As a result, some copper alloys could now conflict with the Directive's new, lower limits for lead.
To help installers comply with their obligations Sanha, the German manufacturer of pipes and fittings, has eliminated lead entirely from some of its ranges of pipes and components on the basis that if a toxic material can be removed, then it should be.
It took Sanha five years to perfect its lead-free manufacturing process for its range of press and threaded fittings. The company's lead-free range includes the Series 3000 threaded red brass fittings; the SANHA-Press Series 8000; and the Series 25000 3-fit-Press fittings for use with copper and composite pipes. Sanha's lead free products are all Water Regulations Advisory Scheme (WRAS) approved as meeting current drinking water regulations.
In addition to the fittings uncompromising quality the advantage to contractors of using Sanha'slead-free components is that if lead is detected in a drinking water system - they can be assured it must have originated upstream from their works - giving them added peace of mind.
22 January 2014