Controlling Legionella in Decorative Fountains

Key points

  • All decorative fountains produce aerosols.
  • Don't place decorative fountains in areas intended for use by persons at increased risk of Legionnaires' disease, such as healthcare facilities.
  • Cleaning and disinfection are a regular part of decorative fountain operation and maintenance.
Illustration of a decorative fountain.


Use this document to:

  1. Help evaluate hazardous conditions associated with decorative or ornamental fountains ("decorative fountains")
  2. Implement Legionella control measures for decorative fountains per ASHRAE Guideline 12
  3. Complement existing resources for water management programs
  4. Support environmental assessments conducted during public health investigations

Key factors affecting Legionella growth‎‎

Sediment and biofilm, temperature, water age, and disinfectant residual are the key factors that affect Legionella growth.


Understanding the decorative fountain design components are critical for Legionella control.

Design recommendations

Consider how each of the following impacts the factors for Legionella growth:

  • Features (e.g., cascades, sprays, water walls)
  • Filtration
  • Lighting
  • Pumps
  • Size
  • Water treatment systems

Cold water supply: Supply decorative fountains with a cold potable water make-up source below the favorable range for Legionella (77–113°F, 25–45°C).

Water management program

Use a water management program to establish, track, and improve operation and maintenance activities.

Operation, maintenance, and control limits

All decorative fountains produce aerosols. Safe operation and regular decorative fountain maintenance protect building owners, employees, and visitors from exposure to Legionella. The necessary frequency of operation and maintenance activities depends on

  • The environmental conditions in the area of the decorative fountain
  • The fountain's design


Operate and maintain decorative fountains of all types and sizes with the following guidelines in mind:

Follow any requirements of the authority having jurisdiction.

Follow all manufacturer recommendations, including those regarding routine cleaning and operation.

Monitor critical water parameters, like temperature and disinfectant residual, at least weekly.

Automate disinfectant feed and monitoring systems, if possible.

Apply algaecide as needed.

Avoid prolonged idle periods. Run decorative fountains at least daily.

Immediately clean and disinfect if any of the following are present:

  • Algae
  • Biofilm
  • Cloudy water
  • Foul odor
  • Visible debris

Consider testing for Legionella in accordance with the routine testing module of this toolkit (linked below).

Remediation during suspected illness

Role of testing

If the authority having jurisdiction suspects an outbreak or illness, test in conjunction with public health in order to:

  • Confirm the presence of Legionella before performing remediation.
  • Confirm Legionella elimination after remediation activities.

Note: The public health authority having jurisdiction determines whether there are associated illness(es) or an outbreak.

Steps to takeA

Remove the decorative fountain from service.

Drain the decorative fountain.

Scrub all surfaces.

Replace filters or filter media (if applicable).

Repair parts as needed.

Refill the decorative fountain.

Hyperchlorinate, maintaining a minimum of 20 ppm free chlorine for 10 hours.

Drain and rinse all components of the decorative fountain.

Refill with fresh potable water.

Return the decorative fountain to the routine disinfectant residual level outlined below before use.

Remediation absent illness

Indications to test

Absent any illness, consider the remediation options described below if control measures are ineffective or routine results indicate poor Legionella control.

Steps to takeA

Remove the decorative fountain from service.

Hyperchlorinate, maintaining 10 ppm free chlorine for one hour.

Drain the water once shock disinfection is completed.

Scrub all surfaces.

Clean and service filters (if applicable).

Refill with fresh potable water.

Return the decorative fountain to the routine disinfectant residual level outlined below before use.

Legionella control measures

Described below are control measures and recommendations for each water parameter.

Sediment and biofilm

Control measures: Cleaning frequency

Recommendations: Any time there is visible biofilm or debris (in addition to routine cleaning bulleted below).

  • <5 gallons: Weekly
  • 5–25 gallons: Monthly
  • >25 gallons: Routinely as indicated by water quality measurements


Control measures: Control limits

Recommendations: Maintain water temperature below 77°F (25°C).

Water age

Control measures: Water turnover, flow, replacement

Recommendations: Water turnover and flow are needed to maintain water treatment applied for microbial control. Avoid idle periods. Run at least daily.

Disinfectant residual

Control measures: Control limits


  • <5 gallons: 3–5 ppm free chlorine for at least 1 hour per day
  • 5–25 gallons: 3–5 ppm free chlorine for at least 1 hour per day
  • >25 gallons: 0.5 ppm free chlorine for at least 6 hours per day
  1. ASHRAE Guideline 12 does not define remedial treatment procedures for decorative fountains. The following procedures are adapted from the ASHRAE Guideline 12 heated whirlpool and spa/hot tub remedial treatment procedure.
  • Exposure to warm air, heat-generating submerged lights, or other factors that elevate water temperature into the favorable growth range (77–113°F, 25–45°C) will require additional mitigation strategies.