Don't Let Water Systems Stagnate

It's important to develop a water management plan to prepare for business re-openings

Don't Let Water Systems Stagnate

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It’s no secret that water quality is negatively impacted by water age in distribution and building systems, and the negative impacts can ultimately affect public health.

In a recent virtual training session, Dr. William Rhoads, research scientist at Virginia Tech, explains how water age can be affected during stay-at-home orders and what we can do to ensure the safety of those using it.

“We are in a unique scenario where stay-at-home orders issued to prevent the spread of COVID-19 has altered the way water is moving through our distribution and plumbing,” Rhoads says. 

Total water age is made up of distribution system water age plus the building plumbing system water age.

“Both are potentially increasing due to COVID-19,” says Rhoads. “To what degree? We don’t quite know yet.”

What is known is that there is widespread concern that it will eventually lead to the development of water quality issues.

“The one that is getting the most attention right now is the growth of Legionella,” says Rhoads. “Legionella is the bacteria that causes Legionnaire’s Disease.” 

The recent increase of this disease is closely related to stagnant potable water.

 “Because the stagnation related to COVID-19 is really a unique experience to many buildings, it brings up the question whether we need to recommission the building,” he says.

This process involves steps to reduce risks from water quality issues that may have developed during prolonged stagnation due to low building occupancy.

Rhoads discusses how much time defines prolonged stagnation and what low occupancy entails.

“I would be looking to see if your building has performed something or has decreased occupancy in response to COVID-19. I think that’s your first and most obvious sign that you should be thinking changes in water quality relative to your normal water use.”

If the building needs to be recommissioned, following a basic flushing order as it applies is a necessary step to remove stagnant water. Begin with hydrant flushing if possible, to remove corrosion, sediment or debris that may have settled in the distribution system that supplies water to the building.

“If you don’t have the ability to do hydrant flushing, the next step would be to focus at the point of entry,” Rhoads says. “You can flush at a high flow rate through the service line. The idea here is to dislodge any sediment or debris in the service line or water main. But make sure you are flushing that down the drain.”

After the point of entry, you’ll want to move onto the mechanical equipment such as water heaters, pressure tanks and water softeners. When those are maintained and flushed, move on to the main branches.

“The idea here is that you want to use a higher flow rate to flush the main branches of your plumbing system. For the cold water that could involve flushing at your riser drains or building chases,” Rhoads says. “For the hot water, I would recommend that you flush at the return line.”

A good rule of thumb is when you see less than 5 degrees Fahrenheit drop from the supply to the return, it indicates that you have started to turn over your hot water system.

“After your main branches you can move to your distal outlets,” he says. “I would flush cold water first, and again you’re looking for that steady temperature.”

After that is achieved, move on to the hot water and flush until you get temperatures that are representative of the water supply temperature.

Once distal outlets are flushed, take care of any special devices that may be in the building. This could include things like ice machines or coffee makers, followed by the non-potable systems like cooling towers or sprinkler systems.

According to Rhoads, the second step for high-level flushing protocol development after flushing the system would be to determine if sampling for Legionella should be conducted and responding appropriately. This can be determined by the amount of time the occupancy has been delayed and how long the water has been stagnant. Rhoads recommends hiring a professional for sampling and interpreting the results before taking action and disinfecting.

“I would never recommend that someone goes in and disinfects a building without having a clear understanding of what risks they are trying to remediate,” he says.

And last, implement routine flushing. Routine flushing can follow the order of flushing previously explained.

“Any building that is sitting stagnant should be considering where their unused taps are and regularly exercising those unused taps to maintain water quality,” says Rhoads. “As a long-term goal, people who are concerned about their water quality should be developing a water management plan as soon as practical.”

Be prepared to develop your own water management strategy and consider adding that service to your business if fitting. Health concerns from stagnant water are often overlooked, especially when so much else is changing during the current pandemic.

To view the full-length Virtual Training session and others like it, check out


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