CMC · California Mechanical Code

How must HVAC condensate drains be sized and routed?

Condensate from HVAC equipment must be carried by a sloped drain (minimum 1/8 in/ft) to an approved disposal point through an indirect connection and sized by the unit’s tonnage per Table 310.3; use corrosion‑resistant materials, provide cleanouts and overflow protection, and follow manufacturer instructions or get AHJ approval for alternate conditions.

Ask a question free See coverage

Last reviewed: July 6, 2026

What the code requires — plain English (controlling §)

Condensate from air‑conditioning and similar equipment must be collected and discharged to an approved plumbing fixture or disposal area and, when entering the building drainage system, must do so by an indirect waste (air gap/air break) with a slope of at least 1/8 inch per foot (1%). This drainage must be sized to match the equipment capacity using Table 310.3 and the pipe material must be compatible with the liquid and temperatures involved. See § 310.1 and § 310.3 for these requirements and Table 310.3 for minimum diameters.

Drain condensate indirectly to an approved receptor, slope the drain at ≥ 1/8 in/ft, and size the pipe per Table 310.3 to match the cooling equipment capacity.

Requirements in detail

Key obligations (short list)

The condensate shall be collected and discharged to an approved plumbing fixture or disposal area; if discharged to the drainage system it must be by indirect waste (air gap/air break). § 310.1.
The condensate waste pipe must have a minimum slope of 1/8 inch per foot (1%) and be of approved, corrosion‑resistant material and not smaller than the outlet size required by § 310.3 or § 310.4. § 310.1.
Sizing of condensate waste pipes from air‑cooling coils is done by equipment refrigeration capacity per Table 310.3. § 310.3.
Condensate piping smaller than 1¼ inch (32 mm) may be PVC, CPVC, PE, PP, copper, or other approved rigid materials; pipes 1¼ inch and larger must be constructed of materials specified in the plumbing code. § 310.3.
Condensate drain lines must allow maintenance access — a cleanout or configuration permitting clearing without cutting is required. § 310.3.1.

Decision‑relevant table (minimum sizes & key values)

Design criterion	Code value / threshold	Code Reference
Minimum slope for condensate waste	1/8 in/ft (1%)	§ 310.1
Pipe sizing (equipment capacity in tons) — minimum pipe diameter	Up to 20 tons → 3/4"
21–40 → 1"
41–90 → 1‑1/4"
91–125 → 1‑1/2"
126–250 → 2"	Table 310.3 (used by § 310.3)
Assumed installation condition for capacity (used by Table 310.3)	Pipe running 3/4 full at 1/8 in/ft slope (1%); specific temperature/air‑mix conditions are assumed by the table	Table 310.3 / § 310.3
Overflow / secondary drain minimum	3/4" nominal for additional pan/drain that discharges to a readily observed point (when required for overflow protection)	§ 310.2 (condensate control)
Materials for < 1¼" condensate piping	PVC, CPVC, PE, PP, copper, or other approved rigid materials (AHJ approval)	§ 310.3
Cleanouts required	Drain configured or provided with a cleanout for blockage clearing	§ 310.3.1

Routing & connection details

Condensate must not discharge over a public way; indirect disposal with an air gap or air break to a trapped/vented receptor (mop sink, dry well, trap tailpiece, etc.) is required. § 310.1 and § 310.5.
Where equipment is in a space that could be damaged by overflow, provide a drain line and secondary protection (water level shutoff, secondary pan with separate drain, higher secondary drain connection, or secondary pan with shutoff). Secondary drains/pans must discharge via a drain not less than 3/4" nominal. § 310.2.
Condensate pumps are allowed with AHJ approval; pump discharge must rise to a point where it can connect to a gravity drain; pumps must be installed per manufacturer instructions and separate sumps and interlocks are required for each condensing unit unless otherwise approved. § 310.1.1.

Exceptions & special cases

Manufacturer sizing and instructions: For condensing appliances, drain lines must be sized according to the manufacturer’s instructions (see § 310.4). If manufacturer instructions differ from Table 310.3, follow the appliance instructions for that appliance.
Slope / conditions other than the table assumptions: If you cannot meet the table’s assumed slope (1/8 in/ft) or the installation differs from the table conditions, the sizing may be adjusted only with Authority Having Jurisdiction (AHJ) approval. § 310.3.
Multiple appliances: Condensate lines serving more than one appliance that connect to a common indirect waste require protections (sanitary waste valve, approved condensate trap or trap primer) at the connection. § 310.4.

Common mistakes

Undersizing pipes by ignoring Table 310.3 (e.g., using 1/2" on a unit that requires 3/4" or 1"). Table is the minimum sizing basis. § 310.3.
Failure to slope the drain at ≥ 1/8 in/ft — standing condensate causes clogging and overflow. § 310.1.
Directly discharging condensate to a public way or to an unapproved receptor without an air gap/air break. § 310.1 and § 310.5.
Not providing a cleanout or routing that prevents non‑destructive maintenance; code requires access for clearing blockages. § 310.3.1.
Using improper material for ≥ 1¼" air‑conditioning waste pipes (must meet plumbing code construction requirements). § 310.3.

Worked example — rooftop packaged unit

Scenario: A rooftop packaged air conditioner rated 50 tons of refrigeration (common for large commercial units). Determine minimum condensate drain pipe size and routing basics.

Use Table 310.3: a unit between 41 – 90 tons requires a minimum 1‑1/4 inch condensate pipe diameter. § 310.3 / Table 310.3.
Install the condensate drain with a slope of at least 1/8 in/ft (1%) so the pipe will operate close to the table assumptions (pipe running 3/4 full at that slope). § 310.1 / Table 310.3.
Select pipe material: since the pipe is 1¼", it is at the threshold where materials must be per the plumbing code (materials for pipes 1¼" and larger are those required by the plumbing code). Confirm material selection per the plumbing code and AHJ. § 310.3.
Provide a cleanout or arrange routing so blockages can be cleared without cutting the line. § 310.3.1.
Route the condensate to an approved receptor via an indirect connection (air gap/air break) — e.g., to a trapped and vented floor sink or mop sink — and avoid discharge over public ways. § 310.1 and § 310.5.
If the unit is located over finished space (possible water damage), provide a secondary pan with a separate 3/4" drain to a readily observed location or a water‑level shutoff device. § 310.2.

Related provisions (quick reference)

§ 310.1 — Condensate disposal (slope, indirect waste, prohibition on public way discharge).
§ 310.2 — Condensate control (overflow protection; secondary pan/drain requirements).
§ 310.3 — Condensate waste pipe material and sizing (use Table 310.3; material rules).
Table 310.3 — Minimum condensate pipe sizes by equipment capacity (tons).
§ 310.3.1 — Cleanouts required for condensate drain lines.
§ 310.4 — Appliance condensate drains (manufacturer sizing, multiple‑appliance connections).
§ 310.5 — Point of discharge (indirect connection to trapped & vented receptors).
§ 310.1.1 — Condensate pumps (installation and interlock requirements).

Code references

Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:

CMC § 310.2.1 High relevance — show source text
310.2.1 Protection of Appurtenances. Where insulation or appurtenances are installed where damage is capable of resulting from a condensate drain pan overfill, such installations shall occur above the rim of the drain

pan with supports. Where the supports are in contact with the condensate waste, the supports shall be of approved corrosion-resistant material.

310.3 Condensate Waste Pipe Material and Sizing. Condensate waste pipes from air-cooling coils shall be sized in accordance with the equipment capacity as specified in Table 310.3. The material of the piping shall comply with the pressure and temperature rating of the appliance or equipment, and shall be approved for use with the liquid being discharged.

TABLE 310.3

MINIMUM CONDENSATE PIPE SIZE

2025 CALIFORNIA MECHANICAL CODE 57

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

GENERAL REGULATIONS

Condensate drain sizing for other slopes or other conditions shall be approved by the Authority Having Jurisdiction.

Air-conditioning waste pipes, 1¼ of an inch (32 mm) and larger in size, shall be constructed of materials specified in the plumbing code. Condensate waste piping less than 1¼ of an inch (32 mm) in size shall be permitted to be PVC, CPVC, PE, PP, copper, or other rigid materials approved by the Authority Having Jurisdiction.

310.3.1 Cleanouts. Condensate drain lines shall be configured or provided with a cleanout to permit the clearing of blockages and for maintenance without requiring the drain line to be cut.

310.4 Appliance Condensate Drains. Condensate drain lines from individual condensing appliances shall be sized as required by the manufacturer’s instructions. Condensate drain lines serving more than one appliance connecting to a common indirect waste pipe shall have the connections to the indirect waste pipe protected by a sanitary waste valve complying with ASME A112.18.8, condensate trap complying with IAPMO IGC 196, or trap with a trap primer.

310.5 Point of Discharge. Air-conditioning condensate waste pipes shall connect indirectly to the drainage system through an air gap or air break to trapped and vented receptors, dry wells, mop sinks, leach pits, or the tailpiece of plumbing fixtures. An individual condensate drain shall be trapped in accordance with the appliance manufacturer’s instructions or in accordance with Section 310.4.

310.6 Condensate Waste from Air-Conditioning Coils. Where the condensate waste from air-conditioning coils discharges by direct connection to a lavatory tailpiece or to an approved accessible inlet on a bathtub overflow, the connection shall be located in the area controlled by the same person controlling the air-conditioned space. 310.7 Female Plastic Connections. Female plastic screwed fittings shall be used with plastic male fittings and plastic male threads. Female plastic threaded connections shall not be allowed to be used when threaded onto a male

metallic connection.

311.0 Heating or Cooling Air System. 311.1 Source. A heating or cooling air system shall be provided with return air, outside air, or both. A heating or cooling air system regulated by this code and designed to replace required ventilation shall be arranged to discharge into a conditioned space not less than the amount of outside air specified in Chapter 4.
CMC § 310.1 High relevance — show source text
310.1 Condensate Disposal . . . . . . . . . . . 57

310.2 Condensate Control . . . . . . . . . . . . 57

310.3 Condensate Waste Pipe Material and Sizing. . . . . . . . . . . . . . . . . . . . 57

Table 310.3 Minimum Condensate Pipe Size. . . 57

310.4 Appliance Condensate Drains . . . . 58

310.5 Point of Discharge . . . . . . . . . . . . . 58

310.6 Condensate Waste from

Air-Conditioning Coils . . . . . . . . . . . 58

310.7 Female Plastic Connections . . . . . . 58

311.0 Heating or Cooling Air System . . . . 58

311.1 Source . . . . . . . . . . . . . . . . . . . . . . 58

311.2 Air Filters . . . . . . . . . . . . . . . . . . . . 58

311.3 Prohibited Sources . . . . . . . . . . . . . 58

311.4 Return-Air Limitations . . . . . . . . . . . 58

311.5 California Energy Code Requirements for Residential

Air Filtration . . . . . . . . . . . . . . . . . . 59

312.0 Plumbing Connections . . . . . . . . . . 59

312.1 General. . . . . . . . . . . . . . . . . . . . . . 59

313.0 Hangers, Supports, and Anchors . . 59

313.1 General. . . . . . . . . . . . . . . . . . . . . . 59

313.2 Material. . . . . . . . . . . . . . . . . . . . . . 59

313.3 Suspended Piping . . . . . . . . . . . . . 59

313.4 Alignment . . . . . . . . . . . . . . . . . . . . 59

313.5 Underground Installation . . . . . . . . 59

313.6 Hanger Rod Sizes . . . . . . . . . . . . . 59

Table 313.6 Hanger Rod Sizes . . . . . . . . . . . . . 59

313.7 Gas Piping . . . . . . . . . . . . . . . . . . . 59

314.0 Balancing . . . . . . . . . . . . . . . . . . . . 59

314.1 General. . . . . . . . . . . . . . . . . . . . . . 59

315.0 Louvers in Hurricane Prone

Regions . . . . . . . . . . . . . . . . . . . . . 59

315.1 General. . . . . . . . . . . . . . . . . . . . . . 59

2025 CALIFORNIA MECHANICAL CODE

316.0 Protection of Piping, Tubing, Materials, and Structures . . . . . . . . 59

316.1 General. . . . . . . . . . . . . . . . . . . . . . 59
CMC § 10.4 High relevance — show source text
The size of condensate waste pipes is for one unit or a combination of units, or as recommended by the manufacturer. The capacity of waste pipes assumes a [1] ⁄ 8 inch per foot (10.4 mm/m) or 1 percent slope, with the pipe running threequarters full at the following pipe conditions:

Outside Air – 20% Col2 Room Air – 80% Col4

DB WB DB WB

90°F 73°F 75°F 62.5°F

For SI units: °C = (°F-32)/1.8

blocked. Such detecting device shall be in accordance with the manufacturer’s installation instructions.

(2) An additional watertight pan of corrosion-resistant material, with a separate drain line, installed beneath the cooling coil, unit, or the appliance to catch the overflow condensate due to a clogged primary condensate drain.

(3) An additional separate drain line at a level that is higher than the primary drain line connection of the drain pan.

(4) An additional watertight pan of corrosion-resistant material with a water level detection device installed beneath

the cooling coil, unit, or the appliance to catch the overflow condensate due to a clogged primary condensate drain and to shut off the equipment.

The additional pan or the additional drain line connection shall be provided with a drain pipe of not less than [3] ⁄ 4 of an inch (20 mm) nominal pipe size, discharging at a point that is readily observed.

310.2.1 Protection of Appurtenances. Where insulation or appurtenances are installed where damage is capable of resulting from a condensate drain pan overfill, such installations shall occur above the rim of the drain

pan with supports. Where the supports are in contact with the condensate waste, the supports shall be of approved corrosion-resistant material.

310.3 Condensate Waste Pipe Material and Sizing. Condensate waste pipes from air-cooling coils shall be sized in accordance with the equipment capacity as specified in Table 310.3. The material of the piping shall comply with the pressure and temperature rating of the appliance or equipment, and shall be approved for use with the liquid being discharged.

TABLE 310.3

MINIMUM CONDENSATE PIPE SIZE

2025 CALIFORNIA MECHANICAL CODE 57

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

GENERAL REGULATIONS

Condensate drain sizing for other slopes or other conditions shall be approved by the Authority Having Jurisdiction.

Air-conditioning waste pipes, 1¼ of an inch (32 mm) and larger in size, shall be constructed of materials specified in the plumbing code. Condensate waste piping less than 1¼ of an inch (32 mm) in size shall be permitted to be PVC, CPVC, PE, PP, copper, or other rigid materials approved by the Authority Having Jurisdiction.

310.3.1 Cleanouts. Condensate drain lines shall be configured or provided with a cleanout to permit the clearing of blockages and for maintenance without requiring the drain line to be cut.
CMC § 305.6 High relevance — show source text
305.6 Outdoor Locations . . . . . . . . . . . . . 55

306.0 Automatic Control Devices . . . . . . . 55

306.1 General. . . . . . . . . . . . . . . . . . . . . . 55

306.2 Building Automation Systems . . . . 56

2025 CALIFORNIA MECHANICAL CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

TABLE OF CONTENTS

307.0 Labeling . . . . . . . . . . . . . . . . . . . . . 56

307.1 Fuel-Burning Appliances . . . . . . . . 56

307.2 Electric Heating Appliances . . . . . . 56

307.3 Heat Pump and Electric Cooling Appliances . . . . . . . . . . . . . . . . . . . 56

307.4 Absorption Units . . . . . . . . . . . . . . . 56

308.0 Improper Location. . . . . . . . . . . . . . 57

308.1 General. . . . . . . . . . . . . . . . . . . . . . 57

309.0 Workmanship . . . . . . . . . . . . . . . . . 57

309.1 Engineering Practices. . . . . . . . . . . 57

309.2 Concealing Imperfections . . . . . . . . 57

309.3 Installation Practices. . . . . . . . . . . . 57

310.0 Condensate Wastes and Control . . 57

310.1 Condensate Disposal . . . . . . . . . . . 57

310.2 Condensate Control . . . . . . . . . . . . 57

310.3 Condensate Waste Pipe Material and Sizing. . . . . . . . . . . . . . . . . . . . 57

Table 310.3 Minimum Condensate Pipe Size. . . 57

310.4 Appliance Condensate Drains . . . . 58

310.5 Point of Discharge . . . . . . . . . . . . . 58

310.6 Condensate Waste from

Air-Conditioning Coils . . . . . . . . . . . 58

310.7 Female Plastic Connections . . . . . . 58

311.0 Heating or Cooling Air System . . . . 58

311.1 Source . . . . . . . . . . . . . . . . . . . . . . 58

311.2 Air Filters . . . . . . . . . . . . . . . . . . . . 58

311.3 Prohibited Sources . . . . . . . . . . . . . 58

311.4 Return-Air Limitations . . . . . . . . . . . 58

311.5 California Energy Code Requirements for Residential

Air Filtration . . . . . . . . . . . . . . . . . . 59

312.0 Plumbing Connections . . . . . . . . . . 59

312.1 General. . . . . . . . . . . . . . . . . . . . . . 59

CMC § 1001.4. High relevance — show source text

270 2025 CALIFORNIA MECHANICAL CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

HYDRONICS

»

shall drain by indirect waste in accordance with Section 1001.4. Embedded piping underground or under floors is not required to be designed for draining the system.

1221.5 Condensate Drainage. Condensate drains from dehumidifying coils shall be constructed and sloped for condensate removal. Such drains shall be installed in accordance

with Section 310.0.

1221.6 Hydronic Fluid Disposal. Hydronic system fluids that contain additives such as antifreeze, corrosion inhibitors, and cleaning solutions shall be recycled or disposed of in an approved manner in accordance with Environmental Protection Agency (EPA), the Department of Health, and as required by the Authority Having Jurisdiction.

1221.7 Clearance to Combustibles. Hydronic piping where the exterior temperature exceeds 250°F (121°C) shall have a clearance of not less 1 inch (25.4 mm) to combustible materials.

2025 CALIFORNIA MECHANICAL CODE 271

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

272 2025 CALIFORNIA MECHANICAL CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE

CHAPTER 13 – FUEL GAS PIPING

(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	Col6	Col7	DSA	Col9	Col10	OSHPD	Col12	Col13	Col14	Col15	Col16	Col17	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	X	X	X	X
Adopt Entire Chapter as amended (amended sections listed below)
Adopt only those sections that are listed below
Chapter/Section

CMC § 814.3 High relevance — show source text
814.3 Condensate Waste Pipe Material and Sizing. Condensate waste pipes from air-cooling coils shall be sized in accordance with the equipment capacity as specified in Table 814.3. The material of the piping shall comply with the pressure and temperature rating of the appliance or equipment and shall be approved for use with the liquid being discharged.

TABLE 814.3

MINIMUM CONDENSATE PIPE SIZE

EQUIPMENT CAPACITY IN TONS
OF REFRIGERATION MINIMUM CONDENSATE PIPE
DIAMETER
(inches)

Up to 20 3⁄4

21 – 40 1

41 – 90 11⁄4

91 – 125 11⁄2

126 – 250 2

For SI units: 1 ton of refrigerant = 3.52 kW, 1 inch = 25 mm

The size of condensate waste pipes is for one unit or a combination of units, or as recommended by the manufacturer. The capacity of waste pipes assumes a [1] ⁄ 8 inch per foot (10.4 mm/m) or 1 percent slope, with the pipe running threequarters full at the following pipe conditions:

Outside Air – 20% Col2 Room Air – 80% Col4

DB
WB
DB
WB

90°F 73°F 75°F ~~62.5°F~~

For SI units: °C = (°F-32)/1.8

Condensate drain sizing for other slopes or other conditions shall be approved by the Authority Having Jurisdiction.

Air-conditioning waste pipes, 1¼ of an inch (32 mm) and larger in size, shall be constructed of materials specified in Chapter 7. Condensate waste piping less than 1¼ of an inch (32 mm) in size shall be permitted to be PVC, CPVC, PE, PP, copper, or other rigid materials approved by the Authority Having Jurisdiction.

814.3.1 Cleanouts. Condensate drain lines shall be configured or provided with a cleanout to permit the clearing of blockages and for maintenance without requiring the drain line to be cut. 814.4 Appliance Condensate Drains. Condensate drain lines from individual condensing appliances shall be sized as required by the manufacturer’s instructions. Condensate drain lines serving more than one appliance connecting to a common indirect waste pipe shall have the connections to the indirect waste pipe protected by a sanitary waste valve complying with ASME A112.18.8, condensate trap complying with IAPMO IGC 196, or trap with a trap primer. 814.5 Point of Discharge. Air-conditioning condensate waste pipes shall connect indirectly to the drainage system through an air gap or air break to trapped and vented receptors, dry wells, mop sinks, leach pits, or the tailpiece of plumbing fixtures. An individual condensate drain shall be trapped in accordance with the appliance manufacturer’s instructions or in accordance with Section 814.4.

TABLE 814.3

MINIMUM CONDENSATE PIPE SIZE

For SI units: 1 ton of refrigerant = 3.52 kW, 1 inch = 25 mm
CMC § 1609.3.1. High relevance — show source text
Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
e. Perimeter fastening areas include three tile courses but not less than 36 inches from either side of hips or ridges and edges of eaves and_gable_ rakes.
f._ Vasd_ shall be determined in accordance with Section 1609.3.1.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s, 1 pound per square foot = 4.882 kg/m2.
a. Minimum fastener size. Corrosion-resistant nails not less than No. 11 gage with5/16-inch head. Fasteners shall be long enough to penetrate into the sheathing3/4 inch or
through the thickness of the sheathing, whichever is less. Attaching wire for clay and concrete tile shall not be smaller than 0.083 inch.
b. Snow areas. Not fewer than two fasteners per tile are required or battens and one fastener.
c. Roof slopes greater than 24:12. The nose of all tiles shall be securely fastened.
d. Horizontal battens. Battens shall be not less than 1 inch by 2 inches nominal. Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
e. Perimeter fastening areas include three tile courses but not less than 36 inches from either side of hips or ridges and edges of eaves and_gable_ rakes.
f._ Vasd_ shall be determined in accordance with Section 1609.3.1.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s, 1 pound per square foot = 4.882 kg/m2.
a. Minimum fastener size. Corrosion-resistant nails not less than No. 11 gage with5/16-inch head. Fasteners shall be long enough to penetrate into the sheathing3/4 inch or
through the thickness of the sheathing, whichever is less. Attaching wire for clay and concrete tile shall not be smaller than 0.083 inch.
b. Snow areas. Not fewer than two fasteners per tile are required or battens and one fastener.
c. Roof slopes greater than 24:12. The nose of all tiles shall be securely fastened.
d. Horizontal battens. Battens shall be not less than 1 inch by 2 inches nominal. Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
e.
CMC § 814.3.1 High relevance — show source text
Condensate drain sizing for other slopes or other conditions shall be approved by the Authority Having Jurisdiction.

Air-conditioning waste pipes, 1¼ of an inch (32 mm) and larger in size, shall be constructed of materials specified in Chapter 7. Condensate waste piping less than 1¼ of an inch (32 mm) in size shall be permitted to be PVC, CPVC, PE, PP, copper, or other rigid materials approved by the Authority Having Jurisdiction.

814.3.1 Cleanouts. Condensate drain lines shall be configured or provided with a cleanout to permit the clearing of blockages and for maintenance without requiring the drain line to be cut. 814.4 Appliance Condensate Drains. Condensate drain lines from individual condensing appliances shall be sized as required by the manufacturer’s instructions. Condensate drain lines serving more than one appliance connecting to a common indirect waste pipe shall have the connections to the indirect waste pipe protected by a sanitary waste valve complying with ASME A112.18.8, condensate trap complying with IAPMO IGC 196, or trap with a trap primer. 814.5 Point of Discharge. Air-conditioning condensate waste pipes shall connect indirectly to the drainage system through an air gap or air break to trapped and vented receptors, dry wells, mop sinks, leach pits, or the tailpiece of plumbing fixtures. An individual condensate drain shall be trapped in accordance with the appliance manufacturer’s instructions or in accordance with Section 814.4.

TABLE 814.3

MINIMUM CONDENSATE PIPE SIZE

For SI units: 1 ton of refrigerant = 3.52 kW, 1 inch = 25 mm

For SI units: °C = (°F-32)/1.8

184 2025 CALIFORNIA PLUMBING CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

INDIRECT WASTES

814.6 Condensate Waste from Air-Conditioning Coils. Where the condensate waste from air-conditioning coils discharges by direct connection to a lavatory tailpiece or to an approved accessible inlet on a bathtub overflow, the connection shall be located in the area controlled by the same person controlling the air-conditioned space. 814.7 Plastic Fittings. Female plastic screwed fittings shall be used with male plastic fittings and plastic threads.

2025 CALIFORNIA PLUMBING CODE 185

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

186 2025 CALIFORNIA PLUMBING CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

CHAPTER 9 - VENTS

(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.)
CMC § 814.2 High relevance — show source text
814.2 Condensate Control. Where any equipment or appliance is installed in a space where damage is capable of resulting from condensate overflow, a drain line shall be provided and shall be drained in accordance with Section 814.1.

An additional protection method for condensate overflow shall be provided in accordance with one of the following:

(1) A water level detecting device that will shut off the equipment or appliance in the event the primary drain is blocked. Such detecting device shall be in accordance with the manufacturer’s installation instructions.

(2) An additional watertight pan of corrosion-resistant material, with a separate drain line, installed beneath the cooling coil, unit, or the appliance to catch the overflow condensate due to a clogged primary condensate drain.

(3) An additional separate drain line at a level that is higher than the primary drain line connection of the drain pan.

(4) An additional watertight pan of corrosion-resistant material with a water level detection device installed beneath

the cooling coil, unit, or the appliance to catch the overflow condensate due to a clogged primary condensate drain and to shut off the equipment.

The additional pan or the additional drain line connection shall be provided with a drainpipe of not less than [3] ⁄ 4 of an inch (20 mm) nominal pipe size, discharging at a point that is readily observed.

814.2.1 Protection of Appurtenances. Where insulation or appurtenances are installed where damage is capable of resulting from a condensate drain pan overfill, such installations shall occur above the rim of the drain

pan with supports. Where the supports are in contact with the condensate waste, the supports shall be of approved corrosion-resistant material.

814.3 Condensate Waste Pipe Material and Sizing. Condensate waste pipes from air-cooling coils shall be sized in accordance with the equipment capacity as specified in Table 814.3. The material of the piping shall comply with the pressure and temperature rating of the appliance or equipment and shall be approved for use with the liquid being discharged.

TABLE 814.3

MINIMUM CONDENSATE PIPE SIZE

EQUIPMENT CAPACITY IN TONS
OF REFRIGERATION MINIMUM CONDENSATE PIPE
DIAMETER
(inches)

Up to 20 3⁄4

21 – 40 1

41 – 90 11⁄4

91 – 125 11⁄2

126 – 250 2

For SI units: 1 ton of refrigerant = 3.52 kW, 1 inch = 25 mm

The size of condensate waste pipes is for one unit or a combination of units, or as recommended by the manufacturer. The capacity of waste pipes assumes a [1] ⁄ 8 inch per foot (10.4 mm/m) or 1 percent slope, with the pipe running threequarters full at the following pipe conditions:

Outside Air – 20% Col2 Room Air – 80% Col4

DB
WB
DB
WB

90°F 73°F 75°F ~~62.5°F~~

For SI units: °C = (°F-32)/1.8
CMC § 309.0 Medium relevance — show source text
309.0 Workmanship.

309.1 Engineering Practices. Design, construction, and workmanship shall comply with accepted engineering practices and shall be of such character as to secure the results sought to be obtained by this code.

309.2 Concealing Imperfections. It shall be unlawful to conceal cracks, holes, or other imperfections in materials by welding, brazing, or soldering, by using therein or thereon paint, wax, tar, solvent cement, other leak-sealing or repair agent.

309.3 Installation Practices. Mechanical systems shall be installed in a manner that is in accordance with this code, applicable standards, and the manufacturer’s installation instructions. All mechanical systems shall be in accordance with construction documents approved by the Authority Having Jurisdiction.

310.0 Condensate Wastes and Control.

310.1 Condensate Disposal. Condensate from air washers, air-cooling coils, condensing appliances, and the overflow from evaporative coolers and similar water-supplied equipment or similar air-conditioning equipment shall be collected and discharged to an approved plumbing fixture or disposal area. Where discharged into the drainage system, equipment shall drain by means of an indirect waste pipe. The waste pipe shall have a slope of not less than [1] ⁄ 8 inch per foot (10.4 mm/m) or 1 percent slope and shall be of approved corrosion-resistant material not smaller than the outlet size in

accordance with Section 310.3 or Section 310.4 for air-cooling coils or condensing appliances, respectively. Condensate or wastewater shall not drain over a public way.

310.1.1 Condensate Pumps. Where approved by the Authority Having Jurisdiction, condensate pumps shall be installed in accordance with the manufacturer’s installation instructions. Pump discharge shall rise vertically to a point where it is possible to connect to a gravity condensate drain and discharged to an approved disposal point. Each condensing unit shall be provided with a separate sump and interlocked with the equipment to prevent the equipment from operating during a failure. Separate pumps shall be permitted to connect to a single gravity indirect waste where equipped with check valves and approved by the Authority Having Jurisdiction.

310.2 Condensate Control. Where any equipment or appliance is installed in a space where damage is capable of resulting from condensate overflow, a drain line shall be provided and shall be drained in accordance with Section 310.1. An additional protection method for condensate overflow shall be provided in accordance with one of the following:

(1) A water level detecting device that will shut off the equipment or appliance in the event the primary drain is

EQUIPMENT CAPACITY IN
TONS OF REFRIGERATION MINIMUM CONDENSATE
PIPE DIAMETER
(inches)

Up to 20 3⁄4

21 – 40 1

41 – 90 11⁄4

91 – 125 11⁄2

126 – 250 2

For SI units: 1 ton of refrigeration = 3.52 kW, 1 inch = 25 mm

CMC § 502.4.3.1 Medium relevance — show source text

E 502.4.3.1 Duct Leakage Verification Test. Ductwork shall be tested to the maximum permitted leakage in 1 cubic foot per minute (ft [3] /min) per 100 square feet [0.0001 (m [3] /s)/m [2] ] of duct surface area in accordance with SMACNA HVAC Air Duct Leakage Test Manual. Register penetrations shall be sealed during the test. The test shall be conducted with a pressure differential of 0.1 inch water gauge (0.02 kPa) across the tested system.

E 502.4.4 Duct Sizing. Duct systems shall be sized in accordance with ACCA Manual D or other methods approved by the Authority Having Jurisdiction with the velocity in the main duct not to exceed 1000 feet per minute (ft/min) (5.08 m/s) and the velocity in the secondary branch duct not to exceed 600 ft/min (3.048 m/s). E 502.5 Insulation for Piping. HVAC system piping installed to serve buildings and within buildings shall be thermally insulated in accordance with Table E 502.5. [ASHRAE 90.2-2007:6.5] E 502.6 Ventilation and Combustion Air. The building shall be designed to have the capability to provide the venti

TABLE E 502.5 MINIMUM PIPE INSULATION THICKNESS [1, 5 ]

[ASHRAE 90.2-2007: TABLE 6.5]

INSULATION CONDUCTIVITY	Col2	Col3	Col4	NOMINAL PIPE DIAMETER (inches)	Col6	Col7	Col8
FLUID DESIGN OPERATING TEMPERATURE RANGE (°F)	Btu•inch/(h•ft2•°F)	MEAN RATING TEMPERATURE (°F)	<1	1 TO 11⁄4	11⁄2 TO 31⁄2	4 TO 6	EQUAL TO OR GREATER THAN 8
HEATING SYSTEMS (STEAM, STEAM CONDENSATE, AND HOT WATER)2, 3	HEATING SYSTEMS (STEAM, STEAM CONDENSATE, AND HOT WATER)2, 3	HEATING SYSTEMS (STEAM, STEAM CONDENSATE, AND HOT WATER)2, 3	HEATING SYSTEMS (STEAM, STEAM CONDENSATE, AND HOT WATER)2, 3	HEATING SYSTEMS (STEAM, STEAM CONDENSATE, AND HOT WATER)2, 3	HEATING SYSTEMS (STEAM, STEAM CONDENSATE, AND HOT WATER)2, 3	HEATING SYSTEMS (STEAM, STEAM CONDENSATE, AND HOT WATER)2, 3	HEATING SYSTEMS (STEAM, STEAM CONDENSATE, AND HOT WATER)2, 3
201–250	0.27–0.30	150	1.5	1.5	2.0	2.0	2.0
141–200	0.25–0.29	125	1.0	1.0	1.

CMC § 307.4 Medium relevance — show source text
(11)Required clearances from combustible surfaces on which or adjacent to which it is permitted to be mounted.

An appliance shall be accompanied by clear and complete installation instructions, including required clearances from combustible other than mounting or adjacent surfaces, and temperature rating of field-installed wiring connections exceeding 140°F (60°C). 307.4 Absorption Units. Absorption units shall bear a permanent and legible factory-applied nameplate on which shall

appear:

(1) The name or trademark of the manufacturer.

(2) The model number or equivalent.

(3) The serial number.

(4) The amount of refrigerant.

(5) The refrigerant designation.

(6) Hourly rating in Btu/h (kW).

(7) The type of fuel approved for use with the unit.

(8) Cooling capacity Btu/h (kW).

(9) Required clearances from combustible surfaces on which or adjacent to which it is permitted to be mounted.

(10)The symbol of an approved agency certifying compliance of the equipment with recognized standards.

56 2025 CALIFORNIA MECHANICAL CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

GENERAL REGULATIONS

308.0 Improper Location.

308.1 General. Piping or equipment shall not be so located as to interfere with the normal use thereof or with the normal operation and use of windows, doors, or other required facilities.

309.0 Workmanship.

309.1 Engineering Practices. Design, construction, and workmanship shall comply with accepted engineering practices and shall be of such character as to secure the results sought to be obtained by this code.

309.2 Concealing Imperfections. It shall be unlawful to conceal cracks, holes, or other imperfections in materials by welding, brazing, or soldering, by using therein or thereon paint, wax, tar, solvent cement, other leak-sealing or repair agent.

309.3 Installation Practices. Mechanical systems shall be installed in a manner that is in accordance with this code, applicable standards, and the manufacturer’s installation instructions. All mechanical systems shall be in accordance with construction documents approved by the Authority Having Jurisdiction.

310.0 Condensate Wastes and Control.

310.1 Condensate Disposal. Condensate from air washers, air-cooling coils, condensing appliances, and the overflow from evaporative coolers and similar water-supplied equipment or similar air-conditioning equipment shall be collected and discharged to an approved plumbing fixture or disposal area. Where discharged into the drainage system, equipment shall drain by means of an indirect waste pipe. The waste pipe shall have a slope of not less than [1] ⁄ 8 inch per foot (10.4 mm/m) or 1 percent slope and shall be of approved corrosion-resistant material not smaller than the outlet size in

accordance with Section 310.3 or Section 310.4 for air-cooling coils or condensing appliances, respectively. Condensate or wastewater shall not drain over a public way.

Frequently asked questions

What if the manufacturer specifies a different drain size than Table 310.3?

Follow the manufacturer’s instructions for that appliance where § 310.4 applies to condensing appliances; appliance manufacturer sizing takes precedence for that unit.

Can condensate be discharged directly outside at grade?

Not if it discharges over a public way. In general condensate must go to an approved receptor and, where entering the plumbing system, by indirect waste (air gap/air break). § 310.1 and § 310.5 apply.

Do condensate drains require traps or vents?

An individual condensate drain shall be trapped in accordance with the appliance manufacturer’s instructions or per § 310.4 when serving appliances; connections to common indirect waste have specific protections. Check § 310.4 for multi‑appliance situations.

What if the drain run cannot maintain 1/8 in/ft?

If you cannot meet the table’s assumed slope (1/8 in/ft) or other table assumptions, resizing or alternate arrangements must be approved by the Authority Having Jurisdiction (AHJ). § 310.3.

Are cleanouts mandatory?

Yes — condensate drain lines must be configured or provided with a cleanout to permit clearing blockages and maintenance without cutting the line. § 310.3.1.

More in California Mechanical Code

Ask about the CMC

Get cited, plain-English answers on the California Mechanical Code for your project — any code section, any scenario.

Start Free Trial

Related in the CMC

What plumbing connection and backflow protections apply to mechanical equipment?

Where can condensate discharge and when are drainage pans required?

Condensate, drainage, and plumbing connections

California Mechanical Code