Elbow dimensions for vent piping

What is going on

For the Goodman vent and intake piping, use medium-radius (1/4 bend DWV) or long-sweep elbows that meet ASTM D3311. A tight elbow adds more resistance than the vent length calculation assumes. If you are not sure what you have in your hand, just measure it, center to face, and compare to the sizes below.

Likely causes

• Short-radius elbow used where a medium-radius or long-sweep is required
• Elbow not meeting ASTM D3311
• Elbow resistance underestimated in the vent length calculation

Check in this order

1. For 2 in. pipe, a medium-radius elbow measures at least 3 1/16 in. from the plane of one opening to the center line of the other.
2. For 3 in. pipe, a medium-radius elbow measures at least 4 9/16 in.
3. Measure each elbow before gluing.
4. Set aside any elbow that comes up short.

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