Chapter 3 — GENERAL REGULATIONS
310.2 Condensate Control — 2025 California Mechanical Code
California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-25 · California
CBSC: official editions, supplements and errata
Italicized text is a California amendment to the model code, as printed in the official publication.
Cite as: 2025 California Mechanical Code (Title 24, Part 4) § 310.2 · Effective January 1, 2026 · Official source: Building Standards Commission
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
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% | Room Air – 80% | ||
|---|---|---|---|
| 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.
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