Multi-Family Homes or Apartments

Multi-family homes include condominiums, apartments, and duplexes. The plumbing system in these buildings may be at higher risk for Legionella than single-family homes because they have larger, more complex plumbing, heating, and cooling systems. Water has further to travel through these systems, so it’s much harder to keep the temperature right, and disinfectant levels adequate.

Multi-Family & Apartments

The control of these systems is typically the responsibility of the landlord, or a property or facility manager. In these circumstances, it is the property or facility manager’s responsibility to ensure proper maintenance and cleaning of the building’s plumbing, heating, and cooling systems. Inside each individual apartment, the tenant should regularly clean showerheads, faucets and personal humidifiers as described on theSingle-family/Townhomes page.

Facility managers of these buildings should follow the recommendations outlined in guidance from the American Society of Heating, Refrigerating and Air-Conditioning Engineers. The ASHRAE standard, (ANSI/ASHRAE Standard 188-2015), outlines how to maintain a building’s plumbing to minimize risk of Legionella, and includes the development of a Water Management Plan, since their buildings may include the following features that can increase the risk of bacterial growth and transmission:

  • Hot tubs/Jacuzzis®/spas
  • Pools and shower facilities
  • Indoor or outdoor fountains or water features
  • Central water heaters and distributed water lines/pipes
  • Cooling towers
  • Water reservoir tanks
  • Humidifiers
  • Solar water systems

Hot Tubs/Jacuzzis® and Spas

Legionella grow best in warm water, like the water temperatures in hot tubs/Jacuzzi® and spas. But, warm temperatures also make it hard to keep disinfectants at the levels needed to kill germs like Legionella. Therefore, facility managers should ensure hot tubs/Jacuzzi®s and spas are periodically inspected by health officials to ensure they are operating properly and adequately cleaned. Facility managers should check the amount of disinfectant in the water and the pH twice a day, and have a regular schedule for cleaning them, which includes scrubbing away slimy films or algae from the sides of the tub, Jacuzzi® or pool. Filters in these units should be replaced in accordance with the manufacturer’s specifications. If Legionella is detected in a hot tub, Jacuzzi®or spa, the facility manager should follow CDC or the American Society for Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) guidelines for cleaning and disinfection.


The CDC outlines guidance for pool operators including a 12-step program for prevention of recreational water illnesses, training, procedures for pool operations, and videos and guidance for the safety handling of pool chemicals. Facility managers should know and obey all applicable laws and regulations. If there are shower facilities associated with pools, facility managers should also be cleaning and disinfecting the shower heads and faucets at least on a quarterly basis.

Water Fountains and Features

Decorative fountains and other water features (e.g., ponds, bird baths, misters, etc.), particularly those that are located indoors, can provide a home for Legionellato grow and be transmitted. Facility managers at buildings with these features should have a written operating procedure for cleaning and disinfecting them to minimize problems from Legionella (and other waterborne bacteria) and they should maintain proper records of treatment and maintenance.

Water Heaters

Multi-family buildings may use a variety of hot water systems, so there is no one-size-fits-all approach to maintenance. If individual apartments have their own water heaters, the guidelines recommended for single-family homes can be used. Legionella typically multiply at water temperatures between 77°F and 108°F. The bacteria are not active below 77°F and do not survive above 108°F. Water heaters should be set to store water at least 140°F and distribute water at 122°F or higher. To minimize the risk of scalding, the thermostatic mixer valves should be fitted as close as possible to outlets. Where mixing valves are not available or feasible, the water heater temperature can be set to 122°F to reduce the risk of scalding, particularly when there are children or the elderly in the building.

Cooling Towers

Large apartment complexes may have a central cooling system that uses cooling towers or evaporative cooling systems. ASHRAE provides procedures for operation and maintenance of these systems in their standard for building water systems. Facility managers working in these buildings should have a water management plan and follow it closely, as numerous Legionella outbreaks have been associated with poor maintenance of cooling systems.


Source: Customer Messaging on Opportunistic Pathogens in Plumbing Systems by the Water Research Foundation