How aging water supply systems can be making us sick

The study, by engineers at the University of Sheffield, is the first to prove conclusively that contaminants can enter pipes through leaks and be transported through the pipe network.
The pressure in mains water pipes usually forces water out through leaks, preventing anything else from getting in. But when there is a significant pressure drop in a damaged section of pipe, water surrounding the pipe can be sucked in through the hole.
It had been assumed that only clean water from the leak would be sucked in, and that even if contaminants were sucked in these would simply be ejected once the pressure returned to normal. The new study has shown, however, that groundwater from around the pipe - which often contains harmful contaminants - can be sucked in, remain in the pipe and travel on through the network.

Dynamic pressure drops happen whenever there is a sudden change in velocity, for example when there are valve or pump failures, or sudden demands on the system, such as when large volumes of water are required for fighting a fire. As a result of engaging with the University of Sheffield research, UK water companies are now training their field staff to limit these pressure drops taking place.
UK drinking water is tested for harmful contaminants and complies with the regulations over 99 percent of the time. But any failure is cause for concern, according to lead researcher Professor Joby Boxall.
Professor Boxall says: "Previous studies have shown that material around water pipes contains harmful contaminants, including viruses and bacteria from faeces, so anything sucked into the network through a leak is going to include things we don't want to be drinking.
"Many of us will have had a 'dodgy tummy' in the past that we couldn't quite explain, often putting it down to something we'd eaten. It now seems possible that some of these illnesses could have been caused not by food, but by water."