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Addressing the dangers of stagnant water in buildings due to COVID-19 shutdowns.


Several facilities have shut their doors as the coronavirus continues to spread throughout the country. Facilities such as schools, office buildings, malls, and the like are being closed down suddenly or choosing to continue operation with a skeletal workforce in order to prevent the further spread of the virus.

Because of this, water systems within the building that store up to hundreds or even thousands of gallons of water have been left stagnant and unattended for long periods of time.

This could lead to several unexpected health hazards like a surge of surface-attached bacteria which can then lead to corrosion problems, and even the growth of premise plumbing pathogens such as Legionella.

Not only can these health hazards lead to prolonged damage of the overall structure of the building overtime, but it can also put the health of those inside the building at serious risk, as exposure to such dangers could lead to severe illnesses and diseases. This is especially dangerous once the buildings are deemed ready to be occupied again in the future.


Although each situation is different, there are practical steps you can take when shutting down a building to help reduce the potential for water system damage and waterborne pathogen growth:

1. Keep the building HVAC systems live to maintain temperature and humidity control.

2. If not required for HVAC system operation, the cooling tower, chillers, heat exchangers, and associated piping should be completely drained. Leaving the system filled with stagnant water can result in severe corrosion, biofouling problems, and contribute to the transmission of Legionnaire’s disease.

3. If the cooling tower is required for HVAC system operation, specific treatment protocols may be required to help address low load conditions. Inhibitor requirements may need to be adjusted, and microbiological control can be more challenging. Do not discontinue water treatment if the tower is being operated.

4. Drain decorative fountains, hot tubs, and pools completely unless approved treatment and monitoring protocols are maintained. 

5. Disconnect the water supply to ice machines, coffee makers, water filters, and similar devices.

6. Disinfect inlet lines and install new filters prior to start up.

7. Keep water heaters set at their designated temperature (ideally at or above 120˜F).

8. Flush all hot and cold water fixtures (showers, faucets, eyewash stations) at least weekly.

9. Document the flushing schedule with log sheets. Routine flushing may mitigate the necessity of disinfecting the potable water system before the building is reoccupied.

10. Periodically monitor the chlorine level at the point of entry and locations throughout the building to ensure flushing provides adequate residuals. Simple test kits are available for chlorine testing.

For more information, contact NCH Chem-Aqua.