Appendix N — IMPACT OF WATER TEMPERATURE ON THE POTENTIAL FOR SCALDING AND LEGIONELLA… — 2025 California Plumbing Code (Title 24, Part 5)

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

Adopting Agency	BSC	BSC- CG	SFM	HCD			DSA			OSHPD							BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting Agency	BSC	BSC- CG	SFM	1	2	1-AC	AC	SS	SS/CC	1	1R	2	3	4	5	6	6	6	6	6	6	6	6	6
Adopt Entire Chapter								X		X	X	X	X	X	X	X
Adopt Entire Chapter as amended (amended sections listed below)
Adopt only those sections that are listed below
Chapter/Section

This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.

526 2025 CALIFORNIA PLUMBING CODE

APPENDIX N

IMPACT OF WATER TEMPERATURE ON THE POTENTIAL FOR SCALDING

AND LEGIONELLA GROWTH

The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency, or referenced in the adopting ordinance.

N 101.0 General.

N 101.1 Applicability. This appendix provides guidelines on the impact of water temperature in minimizing both scalding and Legionella growth potential associated with occupiable commercial, institutional, multi-unit residential, and industrial building plumbing systems.

This appendix shall not include single-family residential buildings. This appendix shall not be considered a risk management guidance document for scalding or Legionella. Where required by the Authority Having Jurisdiction, Legionella risk management shall be in accordance with ASHRAE 188 and ASHRAE Guideline 12.

Note: There are additional factors associated with the potential for scalding and Legionella growth other than temperature.

For scalding potential, other factors include, but are not limited to, user age, health, body part, length of contact time, and water source.

For Legionella growth potential other factors include, but are not limited to, water source and plumbing system: size, design, circulation rate, water age, disinfectant residual, piping material and component complexity.

N 102.0 Definitions.

N 102.1 General. For the purpose of this appendix, the following definitions shall apply: Biofilm. Microorganisms and the slime they secrete that grow on any continually moist surface. Cold Water. Water at a temperature less than 77°F (25°C). Control. The management of the operating conditions to maintain compliance with established criteria. {ASHRAE 188:3} Disinfecting Hot Water. Water at a temperature not less than 160°F (71°C). Disinfection. The process of killing or inactivating microorganism. [ASHRAE 188:3] Halogenation. A chemical reaction that involves the addition of one or more halogens, including, but not limited to, chlorine, bromine, or iodine, commonly used to disinfect water systems.

Hazard. See Risk.

Hot Water. Water at a temperature not less than 130°F (54°C) and less than 140°F (60°C). Legionella Growth Potential. The likelihood that Legionella bacteria will reproduce. Monitor. Observing and checking the progress or quality of (something) or measuring the physical and chemical characteristics of control measures.

Risk. The potential for harm to humans resulting from exposure to Legionella. [ASHRAE 188:3]. Scald Potential. The likelihood of burning the skin. Tempered Hot Water. Water at a temperature not less than 120°F (49°C) and less than 130°F (54°C). Tepid Cold Water. Water at a temperature not less than 77°F (25°C) and less than 85°F (29°C). Tepid Water. Water at a temperature not less than 85°F (29°C) and less than 110°F (43°C). Test. The measurement of the physical, chemical, or microbial characteristics or quality of water. Very Hot Water. Water at a temperature not less than 140°F (60°C) and less than 160°F (71°C). Warm Water. Water at a temperature not less than 110°F (43°C) and less than 120°F (49°C). Water Management Plan. A plan to reduce the risk of Legionella growth and spread.

N 103.0 Building Water System Design Documenta- tion.

N 103.1 Design Documentation. Construction documents shall be required for new construction, renovation, refurbishment, replacement, or repurposing of an occupiable building water system, including a water management plan, and shall be submitted to the Authority Having Jurisdiction.

N 103.2 Onsite Documentation. Documentation shall be maintained onsite and shall be readily accessible to the Authority Having Jurisdiction.

N 104.0 Potential Exposure. N 104.1 Legionella Growth Potential. The Authority Having Jurisdiction shall have the authority to require documentation to address Legionella growth potential, where water temperatures in a water distribution system are within ranges shown in Figure N 104.1 that pose a Legionella growth potential. N 104.2 Scald Potential. Where the water distribution system’s water temperature(s) range poses a scald potential in accordance with Table N 104.2, protection shall be provided in accordance with Chapter 4.

N 105.0 Disinfection.

N 105.1 Disinfection Documentation. Where required by the Authority Having Jurisdiction, documentation for disinfection of all building water systems shall be provided by the registered design professional in the construction documents.

APPENDIX N

N 105.1.1 Copper-Silver Ionization. Copper-silver ionization methods and procedures, shall include the following documentation:

(1) Copper and silver ionization concentrations.

(2) Methods and documentation for monitoring ion levels.

(3) Electrode cleaning cycles and methods.

N 105.1.2 Ultraviolet Light. Ultraviolet light methods shall include the following documentation:

(1) Locations of ultraviolet light units.

(2) Cleaning cycles and methods of the quartz sleeves and housing.

N 105.2 Chemical Disinfection. Chemical biocide treatment shall be permitted to be used in accordance with the following:

(1) Oxidizing biocides in accordance with manufacturer’s guidelines, or as required by the Authority Having Jurisdiction.

(2) Non-oxidizing biocides in accordance with manufacturer’s guidelines.

(3) Alternating the use of different types of biocides, dose, and frequency is recommended.

(4) These treatment methods can be used for continuous, online disinfection or shock treatment online or offline.

(5) Biocides intended for potable water applications shall listed in accordance with NSF/ANSI/CAN 60 and approved by the Authority Having Jurisdiction.

N 105.3 Non-Chemical Treatment. Non-chemical treatment devices shall be permitted to be used in accordance with manufacturer’s guidelines. N 105.3.1 Thermal Shock. Thermal treatment using heat shock at 158°F (70°C) for 30 minutes shall be permitted in accordance with applicable guidelines. N 105.4 Frequency of Cleaning and Disinfection. Where a water management plan is implemented, the frequency of cleaning and disinfection logs shall be readily accessible to the water management team and the Authority Having Jurisdiction.

N 201.0 Supply System Legionella Test Levels.

N 201.1 General. The minimum remediation action for water supply systems shall be in accordance with Table N 201.1.

N 202.0 Emergency Disinfection Procedure. N 202.1 General. An emergency disinfection procedure shall be provided in accordance with Table N 201.1.

For SI units: °C = (°F-32)/1.8

Temperature ranges reported are experimentally determined in a laboratory setting in the absence of a realistic microbial community. Legionella can survive for longer periods of time at temperatures higher and lower than the growth temperature ranges indicated due to changes in their metabolic state and/or protection from thermal disinfection within biofilm or amoeba host organisms.

FIGURE N 104.1

WATER TEMPERATURE RANGES AND LEGIONELLA GROWTH POTENTIAL*

528 2025 CALIFORNIA PLUMBING CODE

APPENDIX N

TABLE N 104.2

WATER TEMPERATURE RANGES AND SCALD POTENTIAL

WATER DESCRIPTION	TEMPERATURE (°F)	SCALD POTENTIAL*
Cold	<77	None
Tepid Cold	≥77 and <85	None
Tepid	≥85 and <110	None Hyperthermia is possible after long exposure in a bathtub or whirlpool tub.
Warm	≥110 and <120	Minimal At 111°F, greater than 220 minutes for second-degree burn.
Tempered Hot	≥120 and <130	Low At 120°F, greater than 5 minutes for second-degree burn, and 10 minutes to third-degree burn; At 124°F, 2 minutes for second-degree burn, and 4 minutes, 10 seconds for third-degree burn.
Hot	≥130 and <140	Moderate to High At 130°F, 18 seconds for second-degree burn, and 30 seconds for third-degree burn.
Very Hot	≥140 and <160	High At 140°F, 3 seconds for second-degree burn, and 5 seconds for third-degree burn; At 150°F, instant for second-degree burn, and less than 2 seconds for third-degree burn; At 158°F, instant for second-degree burn, and less than 1 second for third-degree burn.
Disinfecting Hot	≥160	Immediate

For SI units: °C = (°F-32)/1.8

The infant, elderly, and infirmed have a higher potential for scalding at temperatures lower than listed.

TABLE N 201.1

LEGIONELLA REMEDIATION ACTIONS DOMESTIC WATER SYSTEMS

PERCENTAGE OF POSITIVE LEGIONELLA TEST SITES	REMEDIATION ACTION1
< 30	• Maintain environmental assessment and Legionella monitoring in accordance with the water management plan.
≥ 30	• Immediately institute short-term control measures in accordance with the direction of a qualified professional,2 and notify the Authority Having Jurisdiction, if required. • The water system shall be re-sampled no sooner than 7 days and no later than 4 weeks after disinfection to deter- mine the efficacy of the treatment. • For persistent results, as determined by the Authority Having Jurisdiction, showing = 30 percent positive sites, long-term control measures shall be implemented in accordance with the direction of a qualified professional2 and the Authority Having Jurisdiction. • Retreat and retest. If retest is = 30 percent positive, repeat short-term control measures. • With receipt of results < 30 percent positive, resume monitoring in accordance with the water management plan. • For persistent results, as determined by the Authority Having Jurisdiction, showing = 30 percent positive sites, long-term control measures shall be implemented in accordance with the direction of a qualified professional2 and the Authority Having Jurisdiction.

PERCENTAGE OF
POSITIVE LEGIONELLA
TEST SITES

REMEDIATION ACTION1

< 30

• Maintain environmental assessment and Legionella monitoring in accordance with the water management plan.

≥ 30

• Immediately institute short-term control measures in accordance with the direction of a qualified professional,2
and notify the Authority Having Jurisdiction, if required.
• The water system shall be re-sampled no sooner than 7 days and no later than 4 weeks after disinfection to deter-
mine the efficacy of the treatment.
• For persistent results, as determined by the Authority Having Jurisdiction, showing = 30 percent positive sites,
long-term control measures shall be implemented in accordance with the direction of a qualified professional2
and the Authority Having Jurisdiction.
• Retreat and retest. If retest is = 30 percent positive, repeat short-term control measures.
• With receipt of results < 30 percent positive, resume monitoring in accordance with the water management plan.
• For persistent results, as determined by the Authority Having Jurisdiction, showing = 30 percent positive sites,
long-term control measures shall be implemented in accordance with the direction of a qualified professional2
and the Authority Having Jurisdiction.

Notes: 1 In the event that one or more cases of legionellosis are, or may be, associated with the facility, the sampling interpretation shall be in accordance with the Authority Having Jurisdiction. 2 Control measures shall be included in the water management plan.

530 2025 CALIFORNIA PLUMBING CODE

CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE