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Keeping lead from polluting drinking water

The lower legal limit for lead in drinking water means that contractors now have to think carefully about the copper alloys used in the manufacture of plumbing fittings if they are to avoid falling foul of the European Drinking Water Directive.

Far-reaching changes to the European Drinking Water Directive, DWD98/83/EG, came into force on Christmas Day 2013. The amendments mean more onerous requirements for the microbiological and chemical water quality of drinking water. The most significant change for contractors and installers is a 60% reduction to the current 25µg/litre limit for the lead content of drinking water.

The directive’s new lower limit of 10 µg/litre of lead is even more onerous than might at first appear because up to half of the allowable concentration is permitted to be present in the water supply at point of entry into a dwelling. Where this is the case, even minor quantities of lead leaching into the water supply from copper alloys used to manufacture a pipe fitting or valve may be sufficient to breach the new lead limit.

Up to the 1970s, lead used to be common material for the fabrication of small mains and services pipes. Its use in drinking water systems ceased in the 1970s following concerns that the metal could affect the mental development of children. Nevertheless, traces of lead are still present in many of the alloys used to fabricate pipe fittings and valves.

Heavy metal

Given the concerns about the effects of lead in drinking water, it may come as a surprise to many to learn that some manufacturers still add the heavy metal to brass and other alloys used in drinking water systems in concentrations of around 2% to enhance its machinability. The problem is that, even at these small concentrations, the melting point of lead is generally lower than that of an alloy’s other constituents, which means 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 any lead present over the surface of the alloy, which can then more easily leach into the water supply for a significant time after installation. The only sure way installers can meet their obligations under the Directive is to eliminate lead entirely from an installation.

In response, the more progressive manufacturers of pipes and fittings have invested both time and money in developing lead-free copper alloys. They have also had to invest time and resources in devising new manufacturing systems to process these new alloys. For those few manufacturers that have succeeded, the end result is 100% lead-free press and threaded pipe fittings for use with both copper and composite pipes.

Installers looking for a lead-free drinking water system should also ensure that the lead-free products used are Water Regulations Advisory Scheme approved to meet current drinking water regulations.

Responsible contractors that want to be sure they are using genuine lead-free components should look out for the Pb-free logo on packaging for fittings. That way, if lead is detected in a drinking water system they can be sure it must have originated upstream of their works – which will give them added peace of mind.

Barny Parks is managing director at Sanha UK

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