When a positive test for bacteria or a possible case of Legionnaires’ disease is associated with a building, the owner or water management team should implement an emergency flushing and disinfection protocol.
In part 1 of this series, we discussed the need for emergency flushing and disinfection of the building’s water systems when Legionella bacteria are suspected or confirmed to be present (http://bit.ly/4gyiG5K).
In part 2, we discussed the steps to take before an emergency flushing and disinfection procedure, (http://bit.ly/42HyNsj).
This month, we will continue with the steps for performing and documenting the predisinfection flush, disinfection and postdisinfection flush operations.
Make sure you have completed the preflushing procedures discussed in Part 2 of this column, which include notifying the health department and the building tenants, posting warnings, developing an emergency response plan and taking water samples at key locations for comparison after the flushing and disinfection procedure is completed. That procedure includes preflushing, disinfecting and postflushing to remove the chemicals from the system.
It’s important to have these procedures in place for comparison because if the problem is in the city water main, then flushing from hydrants and considering an on-site secondary water treatment system are necessary. If the municipal water system is contaminated and dosing your system with bacteria, providing a secondary on-site water treatment system allows you to kill the bacteria while in your system.
Legionella testing
1. When performing testing, make sure the team conducting the water sampling and flushing wears respirators, gloves and eye protection, as well as the proper personal protective equipment outlined in the Centers for Disease Control and Prevention’s (CDC) sampling protocols. Aerosols can be generated that can infect the people performing the flushing and disinfection process.
2. Have a cooler ready with sterile swabs, tubes and sterile bulk sampling bottles per the CDC water sampling protocols.
3. Label each sample and document date, time and building/floor/location or room number for each sample collected.
4. Document sampling, flushing and disinfection with photos and notes on emergency flushing and disinfection forms supplied by the consultant.
5. Check with the authorities having jurisdiction (AHJ) or health department to see if they have their own forms that must be completed.
6. If no emergency sampling protocol exists for preflush sampling, follow the CDC’s Sampling Procedure and Potential Sampling Sites Protocol for collecting environmental samples for Legionella culture during a cluster or outbreak investigation or when cases of disease may be associated with a facility.
7. Take two preflush water samples from each location. The first water sample should be the first draw of water from the fitting or faucet, and the second sample should be after running the water for one minute. Sample after one minute of flow in accordance with CDC Legionella water sampling procedures in the following areas:
• At the building’s water service entrance (test port on the backflow preventer) or closest faucet or hose bibb to test for water treatment chemical residuals from the utility.
• At the drain valve on the water heater tank.
8. Collect the first-draw water samples and samples after one minute of flow in the incoming disinfectant residual concentration at each service entrance.
9. Before flushing, take water samples at key locations as determined by the flushing and disinfection contractor for comparison after flushing and disinfection.
10. Measure the temperature and disinfectant residual concentrations in first-draw hot and cold water samples taken in the following locations:
• A point just downstream of the backflow preventer or building service entrance;
• A point just downstream of any water storage tanks, where applicable;
• The top of each riser on a high-rise building’s up-feed system;
• The bottom of each riser on a high-rise building’s down-feed system;
• Sinks and showers on remote floors and wings;
• Remote ice machines and hose bibbs.
11. Take Legionella culture samples and chemical residual test samples from the building service water pipe before any flushing within the building. Determine if a service pipe hose valve for flushing is needed. Flush the building service pipe between the water main and the building service entrance first. If water treatment chemical residuals are not present at the building after flushing three times the volume of the service line, stop flushing and contact the water utility to arrange for flushing the water main at a nearby fire hydrant.
12. Determine the flow rate for each fixture and faucet type.
13. Determine the number of simultaneous fixtures that will need to flow to achieve a predisinfection flushing flow velocity of 3 feet/second (fps) (scouring velocity).
14. Determine the flow volume in the entire piping system and the time required to flush at least three times the system volume with X number of fixtures flowing.
15. Determine the distance from the water treatment plant to the building service entrance to evaluate if water treatment chemical dissipation (water age) is an issue. If so, consider an on-site secondary water treatment system after the water service entrance.
16. All water heaters and heat-generating equipment should be turned off prior to flushing and chemical disinfection of the building water systems. This is because heat can rapidly oxidize the chemicals.
17. Flush the entire hot water system and document flushing at each outlet (a minimum of three times the volume at a velocity of 3 fps).
Three times the volume is due to water flowing faster down the center of the pipe, and it takes two-and-a-half to three times the volume to remove all the turbidity from the piping system. Authorities have determined that flushing at 3 fps velocity is required to move (scour) sand and sediment off the bottom of the pipe.
18. Flush the entire cold water system and document flushing at each outlet (a minimum of three times the volume at 3 fps velocity).
19. When flushing begins, open one or two plumbing fixtures at the top of each riser and at the end of each branch of the building drain.
20. Determine the sanitary drain pipe sizes and capacities at half-full flow to ensure that fixture or drain flooding will not occur during flushing. Position staff in lower areas prone to backup and flooding with radios or phones to notify someone standing by the service valves, or have them shut off the service valves if there is a drain backup or flooding problem.
21. Determine how many workers will be needed to perform the flushing and disinfection tasks.
22. Before turning off or adjusting the hot water system, photograph and document, in writing, the temperature set-point on the water heater thermostat dial or panel (see engineer’s design drawings and ASHRAE Guideline 12 for recommended temperatures after procedure).
23. Before turning off or adjusting the hot water system, photograph and document the temperature measured on the water heater discharge pipe temperature gauge. Note if the temperature gauge/thermometer is broken or not working properly (see the engineer’s design drawings and ASHRAE Guideline 12 for recommended temperatures after procedure).
24. Before turning off or adjusting the hot water system, if a thermostatic mixing valve (TMV) is present, photograph and document the temperature measured on the TMV discharge pipe temperature gauge. Note if the temperature gauge/thermometer is broken or not working properly.
Also, note the ASSE standard number and verify the piping arrangement and valving with photos (see engineer’s design drawings and ASHRAE Guideline 12 for recommended temperatures after procedure).
25. Before turning off or adjusting the hot water system, photograph and document the temperature measured from the water heater drain valve at the bottom of the tank (after the draining hot water temperature stabilizes during flow from the drain). (See the engineer’s design drawings and ASHRAE Guideline 12 for recommended temperatures after the procedure.)
26. Before turning off or adjusting the hot water system, photograph and document the temperature on the water heater thermostat dial or panel (see engineer’s design drawings and ASHRAE Guideline 12 for recommended temperatures after procedure).
27. Before turning off or adjusting the hot water system, photograph and document the temperature in the storage tank (see engineer’s design drawings and ASHRAE Guideline 12 for recommended temperatures after procedure).
28. Determine the chlorine disinfectant concentration and minimum contact time of the water/chlorine solution required for the emergency disinfection procedure. Adjust disinfection levels based on the compatibility of the piping system material with chlorine (see Table). Chlorine is commonly used for emergency disinfection because it is inexpensive, readily available and highly effective.
In addition, check with the manufacturers of the pipe and fittings, valves, and equipment to see if they have a chemical compatibility chart that lists the maximum level of chemical that the pipe and fittings, valves, and equipment can be exposed to.
29. Add chemical disinfectant. Record the disinfection chemical residual levels at the first downstream valve or fixture and at the farthest fixture every 30 minutes or periodically throughout the disinfection process.
30. Record the PH levels and total dissolved solids in the water at a remote fixture to assist with adjustments to the chlorine levels based on the water quality.
31. Follow the chlorine levels in the Table to avoid any adverse impact on plumbing materials, including metals, plastics and gaskets. In addition, check with the manufacturers of the pipe and fittings, valves, and equipment to see if they have a chemical compatibility chart that lists the maximum level of chemical that the pipe and fittings, valves, and equipment can be exposed to.
32. Note any chlorine chemical concentrations above the AHJ’s limits. Water use restrictions should be in place during emergency flushing and disinfection procedures.
33. Perform Legionella culture testing. This allows the Legionella strain and type to be identified, similar to DNA testing. It can help determine if there is a match with the Legionella in sick people and any that might be found in the building.
34. Photograph and document all culture tests for Legionella. Note the collection locations and times (see CDC Legionella sample collection document).
35. Flush water through every part of a building water system with sufficient flow velocity and volume (three times the system volume) to flush out all stagnant water and replace it with fresh water. High-velocity flushing will remove sediment and debris from plumbing systems.
36. After preflushing all the stagnant water, a chemical disinfectant is applied with close control on chemical levels and contact times so as not to cause damage or excessive oxidation to the piping system and components.
37. After the contact time is met, immediately perform a postdisinfection flush to remove all chemical disinfectants using the same volume of flushing water as the preflush. This ensures all parts of the piping system are flushed of excess chemicals before performing a postflush water sampling and testing for water treatment chemical residuals.
38. Check for water features and fountains.
39. Check for hot tubs, swimming pools and spas.
40. Check for evaporative cooling systems (cooling towers).
41. Check for humidification systems.
42. Check for other sources of aerosols in the building water system, such as plumbing fixtures.
The owner of a building where there has been an outbreak of positive tests for Legionella in the system should consider establishing a water management program. This requires assembling a water management team and then hiring a certified expert with Legionella and water management to provide a risk assessment report of the building’s water systems.
The report is reviewed by the water management team, which then develops a water management plan based on an assessment of the specific risks at the building or site.
This could take weeks or months to fast-track a building risk assessment, assemble a team and write a plan with protocols for preventive maintenance, monitoring and establishing control parameters, as well as a protocol for responding to a suspected case or a positive test for Legionella bacteria.
