Trap Arm & Fixture Trap Calculator
Determine trap arm limits and trap requirements
Proposed Installation
From trap weir to vent connection
Trap Arm Analysis
Maximum Trap Arm Length
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Status
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Minimum Trap Size
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Required Trap Seal
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Max Vertical Distance
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Trap Arm Length Limits (UPC)
| Trap Size | Max Length | Fall |
|---|---|---|
| 1-1/4" | 30" | 1/4"/ft |
| 1-1/2" | 42" | 1/4"/ft |
| 2" | 60" | 1/4"/ft |
| 3" | 72" | 1/8"/ft |
| 4" | 120" | 1/8"/ft |
Fixture Trap Requirements
| Fixture | Min Trap Size | DFU | Notes |
|---|---|---|---|
| Lavatory | 1-1/4" | 1 | P-trap required |
| Kitchen Sink | 1-1/2" | 2 | Disposal may require 2" |
| Bathtub | 1-1/2" | 2 | Drum trap prohibited in new work |
| Shower | 2" | 2 | Check drain strainer size |
| Clothes Washer | 2" | 2 | Standpipe 18-42" height |
| Floor Drain | 2" | 2 | Trap primer may be required |