New research is the first to prove contaminants can enter drinking water pipes through leaks, putting humans at risk.
The pressure in water pipes forces water out through leaks, and prevent contaminants from entering, the University of Sheffield reported. When there is a drop in pressure, it can cause water surrounding the pipes to be sucked in through the damaged areas.
Past research has suggested any contaminants that entered the pipes under these conditions would be ejected once the pressure returned, but this new study shows the harmful substances can actually be circulated through the pipe network.
Drops in pressure can occur when there is a sudden change in velocity triggered by valve or pipe failures, or sudden system demands such as large volumes of water needed to fight a fire.
"Previous studies have shown that material around water pipes contains harmful contaminants, including viruses and bacteria from [feces], so anything sucked into the network through a leak is going to include things we don't want to be drinking," said lead researcher Professor Joby Boxall. "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."
To make their findings, the researchers used a purpose-built test facility made up of pressure-controlled water pipes. A section of the water pipe was damaged, and the leak was enclosed by a box containing gravel laced with dye that acted as a contaminant. They found when the damaged region was subjected to a dynamic pressure drop, up to 60 milliliters of the dye was sucked into the pipes and traveled throughout the pipe network.
"Our research shows that contaminants that enter through a leaking pipe could be reaching consumers' taps, and although this will be at very low concentrations, it would fail the safety tests if detected. We also believe that microorganisms, including pathogens, which enter the network in this way could attach to the inner surface of the pipe and multiply. If they are later dislodged by another change in flow, they could then reach our taps in higher concentrations," said co-researcher Richard Collins.
The findings were published in a recent edition of the Journal of Hydraulic Engineering.
