HVAC (C-20) · Lesson 4 of 6

Condensate Drains: Pipe Size, Slope, and Overflow Protection

"Condensate Drains: Pipe Size, Slope, and Overflow Protection" is lesson 4 of 6 in the HVAC (C-20) Learning Hub. It opens with "Cooling Coils Make Water Every Hour They Run" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Cooling Coils Make Water Every Hour They Run
  2. Size the Pipe by Tons - CMC Table 310.3
  3. Slope and Cleanout
  4. Where It Ends: Indirect Waste and Traps
  5. Overflow Protection

The worked example in the course applies this lesson to a realistic job in 5 steps, from "Find the pipe size" through "Compare to the height available".

What you'll be able to do

  • Explain the main idea of "Condensate Drains: Pipe Size, Slope, and Overflow Protection" in plain language you can use on the exam.
  • Apply this step with confidence: "Slope and Cleanout".
  • Apply this step with confidence: "Where It Ends: Indirect Waste and Traps".
  • Apply this step with confidence: "Overflow Protection".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Condensate Drain: Size, Slope, and Air GapAIR HANDLER30 tonsFall = 64 x 1/8 = 8 in.Pipe: 1 in. (Table 310.3)Pan outlet to rim:12 in.RECEPTOR1 in.air gapNot to scaleCMC Table 310.3Up to 20 tons3/4 in.21 - 40 tons1 in.41 - 90 tons1-1/4 in.91 - 125 tons1-1/2 in.126 - 250 tons2 in.Our unit: 30 tons = 1 in. minimumSlope: 1/8 in. per ft (1 percent)Fall: 64 ft x 1/8 = 8 in.8 + 1 air gap = 9 of 12 in. OK30 tons: 1 in. pipe, 8 in. of fall, 1 in. air gap. It fits in 12 in.Where overflow could cause damage, add an auxiliary drain or a water-level shutoff.California Mechanical Code Section 310 and Table 310.3; California Plumbing Code 801.2 (air gap).CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Cooling Coils Make Water Every Hour They Run

An air-conditioning coil removes moisture from the air, and a condensing appliance makes condensate from its exhaust. CMC Section 310.1 requires condensate from air-cooling coils, condensing appliances and similar equipment to be collected and discharged to an approved plumbing fixture or disposal area, and it may not drain over a public way. Where it enters the drainage system it goes through an indirect waste pipe sloped not less than 1/8 inch per foot (1 percent) and made of approved corrosion-resistant material not smaller than the outlet size.

Step 2: Size the Pipe by Tons - CMC Table 310.3

CMC Section 310.3 sizes condensate waste pipes from air-cooling coils by equipment capacity in tons of refrigeration: up to 20 tons = 3/4 in.; 21 to 40 tons = 1 in.; 41 to 90 tons = 1-1/4 in.; 91 to 125 tons = 1-1/2 in.; 126 to 250 tons = 2 in. The sizes apply to one unit or a combination of units, or as the manufacturer recommends. A big commercial unit does NOT get the 3/4 in. pipe you use at a house.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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