If Your Home Water Supply Line Has Metal Pipes, Experts Warn It’s a Breeding Ground for Bacteria
Discoloration and off-tasting tap water are often shrugged off as a usual household problem. It’s time people realized the dangers of stagnant water in taps because it may lead to serious health risks. A new study led by an international team of researchers from Inner Mongolia University (IMU) in China and the Technical University of Madrid (UPM) has found that tap water contributes to an “invisible yet widespread issue” stemming from drinking unchecked tap water. The research indicates that the metals in water pipes react with bacteria, helping them thrive and form thin biofilms inside the pipes– a public health concern. The study was published in the journal Clean Water, per Smart Water Magazine.
Not just in theory, the researchers intended to demonstrate the bacterial phenomenon and studied 2 liters of tap water collected from a city in China and analyzed it after keeping it stagnant in a dark room for some time. The team of researchers took water samples in Hohhot, a city with 3.5 million inhabitants, who utilize chlorinated tap water. After 20 minutes of water collection, the team stored the two-liter samples in conditions simulating a stagnant water pipe. They added small glass beads to facilitate the bacterial adhesion and allow them to form the expected biofilms.
“Over time, we analyzed both the water and the biofilms—those thin bacterial layers that formed on the glass beads—to understand how microorganisms develop in stagnant water. Our goal was to expose invisible risks that could be present in any household and provide evidence to support safer drinking water policies and better plumbing design practices,” said the lead researcher of the study, Professor Ling Feng. The results found iron as one of the most risky factors influencing bacterial growth. Turns out, stagnant water in pipes for days, even hours, does form sticky biofilms on the interior surface of the pipes.
Even minute amounts of iron allow harmful bacteria like Salmonella enterica and Pseudomonas aeruginosa to thrive, explained Feng. Following the study, iron in plumbing became a point of concern due to its potential link to harmful bacteria and resistance genes. More importantly, such conditions may lead to antibiotic resistance and cause deadly diseases that would be untreatable. The easiest way to understand if a pipe is infested with bacteria would be water discoloration and the metallic taste in the tap water.
Stefanos Giannakis, a researcher at the School of Civil Engineering at the UPM, said, “We wanted to understand what happens to drinking water when it remains stagnant in pipes for long periods. Specifically, we sought to examine whether small amounts of metals, such as iron and aluminum, influence bacterial growth and whether this, in turn, contributes to the spread of antibiotic-resistant bacteria.”
He contributed to the study, which highlights the underlying risks of tap water running in homes across the world, and encourages stringent water policies. While there are different pipes used for plumbing homes now, like PVC pipes, iron is still found in older homes and in areas with well water as the source. The primary reason for the switch from iron to PVC is odor, staining, bad taste, and buildup in pipes, which obstructs the water flow, per ScienceDirect.