Guidance for Monitoring Building Water

Maintain hot water temperature at the return at the highest temperature allowable by state regulations or codes.

Centers for Disease Control and Prevention. Guidelines for environmental infection control in health-care facilities: Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committeepdf icon. MMWR. 2003;52(RR-10):1–42.

D. Recommendations—Water
D.II. Routine Prevention of Waterborne Microbial Contamination Within the Distribution System

  1. Maintain hot water temperature at the return at the highest temperature allowable by state regulations or codes, preferably ≥124°F (≥51°C), and maintain cold water temperature at <68°F (<20°C). Category IC (States; ASHRAE: 12:2000)
  2. If the hot water temperature can be maintained at ≥124°F (≥51°C), explore engineering options (e.g., install preset thermostatic valves in point-of-use fixtures) to help minimize the risk of scalding. Category II
  3. When state regulations or codes do not allow hot water temperatures above the range of 105°F–120°F (40.6°C–49°C) for hospitals or 95°F–110°F (35°C–43.3°C) for nursing care facilities or when buildings cannot be retrofitted for thermostatic mixing valves, follow either of these alternative preventive measures to minimize the growth of Legionella in water systems. Category II
    1. Periodically increase the hot water temperature to ≥150°F (≥66°C) at the point of use. Category II
    2. Alternatively, chlorinate the water and then flush it through the system. Category II
  4. Maintain constant recirculation in hot-water distribution systems serving patient-care areas. Category IC (AIA: 7.31.E.3)
Measure the pH of your water to determine whether the disinfectant used in your building will be effective. Disinfectants work best within a narrow pH range.

Environmental Protection Agency. Technologies for Legionella Control in Premise Plumbingpdf iconexternal icon. 2016.

2.3.1.4 Operational Conditions

Parameter Conditions Indicating Operational Effectiveness

The efficacy of chlorination is affected by many factors, including chlorine concentration, contact time, pH, temperature, turbidity, buffering capacity of the water, concentration of organic matter, iron and the number and types of microorganisms in the water system (in biofilms and free-living)… The bactericidal action of the chlorine is enhanced at higher temperatures and at lower pH levels. The anti-microbial efficacy of chlorine declines as pH increases >7, with significant loss of efficacy at pH >8. However, free chlorine is degraded rapidly at elevated water temperatures, which is a concern for hot water chlorination (Health Protection Surveillance Centre, 2009)…

2.3.2.4 Operational Conditions

Parameter Conditions Indicating Operational Effectiveness

…The rate of reaction for the conversion of chlorine to monochloramine is sensitive to pH and can also be affected by contact time and temperature. The optimum pH range for formation of monochloramine is 7.5 to 9 (WHO, 2004)