December 14, 2019

Lead Solder use and the quality of drinking water in UK buildings


The purpose of this paper is to update plumbers and water authorities by drawing on scientific research and robust studies about the dangers of lead solder and its widespread use in homes, schools and colleges in the UK. 

In a social media post, Wessex Water recommended ‘starting the day with a large glass of tap water’ without consideration for the quality of water being first drawn after overnight stagnation. When water stagnates over-night there is a risk of toxic chemicals like lead leaching into the water from plumbing, drinking water taps and water heaters located inside the building. However, Wessex Water are not the only water authority in the UK making assumptions about the quality of drinking water in buildings. 

When challenged about this statement Wessex Water replied that they had no lead water mains in use in their region – which is commendable. They provided the following link Lead pipes and your water which was not provided in their first social media promotion of home tap water – the link provided the following information for home owners to assess the risk of lead in their home depending upon its age. 

When was your house built?

First it is worth finding out when your home was built. If it was built:

From 1985 onwards, there shouldn’t be lead present in your plumbing system

Between 1970 and 1985 it is unlikely you will have lead pipes but lead based solder may have been used to join copper pipes

Before 1970 you have lead pipes in your plumbing system

Wessex Water

The use of lead solder on drinking water supplies in new and existing UK buildings

Since the Safe Drinking Water Act (1986) the use of lead-containing solders in potable water systems has effectively been banned nationwide. The dangers of lead to humans are well documented – World Health Organisation has identified lead as 1 of 10 chemicals of major public health concern, needing action by Member States to protect the health of workers, children and women of reproductive age. Lead has been found to be the cause of hypertension, cardiovascular disease and memory loss in adults – in children lead causes ADHD and other developmental and behavioural problems – in pregnant women the unborn child can be harmed – and lead has been found to be probably carcinogenic. 

Despite the publicised health risks with lead, some 14 years after it was banned, a study conducted on Scottish new homes found it was still being used on drinking water plumbing. The general conclusion from  The Scottish New Homes Lead Survey Stage 1 and 2 (2000-2003) are outlined below:

Stage 1 and Stage 2 of the Scottish New Homes Lead Survey therefore provide objective evidence that 

  • Leaded solder was used (illegally) on drinking water plumbing in new houses across Scotland
  • Leaded solder was the most likely source of excess lead contamination in the drinking water of the houses sampled
  • The correlation of lead levels in blood with lead levels in the drinking water of affected houses, together with the similarity in the isotope ratios between lead in blood and water, is consistent with the lead derived from leaded solder being absorbed by the house occupants
  • House occupants were therefore exposed to an additional quantity of lead from a preventable source of contamination 
  • The use of leaded solder represents an avoidable hazard in terms of an unnecessary additional body of burden of lead and a potential cause of lead toxicity, especially for vulnerable groups including very young children and pregnant women
  • The proportion of new houses identified by Stage 1 of the survey as being affected by the use of leaded solder, could be more than twice the original estimate of 15%

Stage 2 of the Scottish (2003) study stated that overnight water samples identified the greatest number of houses with excess lead levels. It was stated that random sampling underestimated the number of affected houses by more than 50% – Stage 1 estimated 15% of samples had excess lead levels attributable to lead solder and 31.4% of houses built in Scotland in 2000 had excess water lead levels. It was argued that the figures were considerable underestimates and the use of leaded solder could therefore have been significantly more common than was originally thought. 

At the time of stage 1 of the study (2000) a member of the Scottish and Northern Ireland Plumbing Employers Federation (Snipef) wrote a letter (dated: 31 May 2000) which opened with the following comment:

Hello Gentlemen.

I am delighted as a member of Snipef to see your concern regarding the use of lead solder in potable plumbing situations. I assume that this action is in relation to the threat on public health and I thoroughly endorse the ban of lead solder if plumbers are not willing to use it correctly…

It is a subject never mentioned at training colleges, the public are unaware of their danger in either long or short term use of water of this nature. 

Instead of Snipef responding to calls from members for an outright ban on lead solder they are currently one of a number of organisations still promoting Lead solder use in the UK some 20 years later. Snipef support the Water Regulations Advisory Scheme (WRAS) who still recommend the use of lead solder on heating systems (see here).

Reddy (2018) reported the widespread use of lead solder for training purposes in Further Education colleges because it is much cheaper than lead-free solder. Not only do UK colleges often breach the water regulations, they arguably increase the risk of mistakes by ‘unapprenticed’ or partially-trained plumbing students who use the short courses as a launch-pad into self-employment as legitimate plumbers. It could be argued that these students may be more inclined to use lead solder on potable supplies because they have only learned plumbing in a college and often work unsupervised as self-employed plumbers. The wider research gives published evidence that plumbers still use lead solder illegally or accidently in jointing drinking water copper pipes (Ramsay et al 2002 cited here p.23). 


This paper provides sufficient evidence to suggest water companies are not meeting their obligations to the public in giving robust safety advice on an important matter of the quality of water for drinking at the tap. Although drinking water may be clean when it leaves the water authority treatment plant it can be contaminated from infrastructure pipes and more specifically when it enters a building and stagnates over night in the presence of copper pipes with lead solder joints.

Although the legal use of lead solder has become a contested issue with WRAS recommending that it is legal for use on heating systems – the use of lead solder represents an avoidable hazard in terms of an unnecessary body burden of lead and potential cause of poisoning of vulnerable groups including very small children and pregnant women. Suitable alternatives to lead solder are widely available – plumbing and water authorities should be following WHO guidelines in taking all other practical measures to reduce total exposure to lead, including the implementation of corrosion control in plumbing systems – this means a ban on lead solder use in building distribution systems which include heating and gas pipe work.