Water quality: low-flow plumbing for green buildings could be problematic, study says

A new study shows that commercial buildings with low-flow designs can have water quality safety issues, in part due to long-term stagnant water.

Researchers studied water quality in a three-story commercial building in Indiana over three weekends from January to February 2020.

Their goal was to find out if water quality would change over the weekend when fewer people were in the building and therefore even less water moving through the pipes than usual.

The answer appears to be yes, according to results published Wednesday in the journal PLOS Water.

“Weekend stagnation affects biological and chemical water quality, with obvious differences in several parameters on Friday, after a week of use, and Monday, after a weekend with relatively little water is used,” the study said.

Although the study was conducted before the pandemic, the findings raise concerns that commercial buildings that remained mostly empty for months during the closure could still have drag water quality issues. long derived from that time.

The building that the researchers looked at is one of more than 100,000 buildings in the United States that are certified green with the American Green Building Council. These are buildings designed, among other things, to reduce the amount of water used for the works compared to conventional buildings, all with the aim of making the building more environmentally conscious. school.

This means less water flows through the plumbing. However, while this can be beneficial for water conservation, questions remain as to what affects water quality.

The researchers took samples from 12 locations in the building, including areas like bathroom sinks or kitchen faucets. Sampling was performed on Friday evenings and Monday mornings for three weeks to measure water quality before and after each weekend.

They then tested for pH, metals, ions, and Legionella bacteria, a strain of bacteria that can grow and spread in water systems and potentially cause a severe form of pneumonia known as Legionnaires’ disease. .

Inside the building, water passes through welded copper pipes. The study said water from the city’s public water system “is used for drinking, equipment and sanitation, while stormwater is collected and routed separately for toilet flushing and irrigation.” research said.

When comparing different sampling locations, the researchers found that water quality varied depending on the faucet, possibly due to the frequency with which certain fixtures were used, the researchers suggest. know.

Levels of Legionella were found at the highest levels in a particular sink and shower in the bathroom in the same bathroom on the first floor. Showers were not used by anyone throughout the study and samples were obtained from plastic showerheads.

Showers are considered to be a unique biofilm growth niche that may support pathogens, the study notes, adding that water can collect in showerheads. weeks or even months before sampling.

As for how the water changed over the weekend with less use, the researchers noticed a clear increase in copper and lead levels in the water over the weekend.

In sampling sites supplied with water by a particular pipe, there were levels of copper in the water above what is considered healthy enough for drinking water.

They also found that chlorine levels fluctuated, with levels consistently lower on Mondays than on Fridays – a concern given the role chlorine plays in preventing the growth of microorganisms like Legionella that occurs outside. in the plumbing system.

The researchers found no significant change in Legionella counts from Friday to Monday, and noted that no Legionella pneumoniaophila, the more dangerous bacteria, was found in the building.

And while water quality clearly changes over the weekend when less is used, the researchers haven’t completely untangled the mechanisms between stasis and water quality.

While heavy metals are known to leach out more from pipes when water is stagnant, the researchers found no consistent trend when comparing chemical levels with the hours of stagnation given. is happening in each pre-sampling context. More comprehensive documentation of water use is needed in further studies to draw more complete conclusions, the researchers say.

But they say there is clearly a need for further investigation.

Water usage patterns in office buildings, often low or unused on weekends, add to concerns about water quality for early users, the researchers said. Monday morning,” the researchers said.

This research doesn’t mean we should abandon water-saving practices or discard green initiatives – but more research can help create safety parameters that keep pace with advances. eco-friendly sets, research shows.

“The first people to arrive at the office on Monday morning may, in fact, be using contaminated drinking water,” the authors added in a press release. “In order to better understand whether the water we are using is safe or not, more testing of the tap water is needed. Plumbing design standards and codes must also be revised”.