Install a Sink Drain Trap Assembly

A. Finished-Project Specification

Quantity: one complete trap assembly consisting of one trap bend, one cut-to-length trap arm, matched slip-joint nuts and washers at the tailpiece connection and the wall-adapter connection, installed on the existing approved tailpiece and wall adapter.

B. Component Schedule

Component	Quantity	Material	Finished Size	Preparation
Trap bend	1	Matched to existing tailpiece and drain-size material (e.g., ABS, PVC, or chrome-plated brass as approved)	Matched to existing tailpiece and wall-adapter diameter	Dry-fit before final assembly; inspect sealing surfaces for damage
Trap arm	1	Matched to trap-bend and wall-adapter material	Cut square to the controlled length recorded on the worksheet	Cut, deburr, and label before assembly
Slip-joint nut, tailpiece end	1	Matched to tailpiece and trap-bend threading	Sized to tailpiece diameter	Inspect threads; hand-fit before final tightening
Slip-joint nut, wall-adapter end	1	Matched to trap-arm and wall-adapter threading	Sized to trap-arm diameter	Inspect threads; hand-fit before final tightening
Slip-joint washers	2 (minimum)	Manufacturer-specified for the installed nuts	Matched to nut and pipe diameter	Orient beveled or tapered face per manufacturer instruction before assembly
Tailpiece extension (if required)	0–1	Matched to existing tailpiece material and diameter	Length required to reach the trap bend within approved insertion depth	Install only if the existing tailpiece length does not reach the trap bend correctly

C. Material Takeoff

• Trap components: one trap bend and one length of trap-arm stock sufficient to cut the controlled length recorded on the worksheet, with allowance for one recut if the first cut is misjudged.
• Slip-joint hardware: two slip-joint nuts and a minimum of two matched slip-joint washers, plus one spare washer set in case a washer is damaged during assembly or disassembly.
• Protection materials: cabinet and floor protection sheeting, a container sized to catch retained water, and absorbent material for cleanup.
• Documentation: one Sink Trap Assembly Worksheet per project, plus a photograph of the original assembly and the completed assembly.

D. Fastener and Hardware Schedule

Joint	Fitting	Orientation	Tightening Method	Seating Condition
Tailpiece to trap bend	Slip-joint nut and washer	Washer beveled or tapered face per manufacturer instruction; nut threads engaged squarely	Hand-tighten fully, then apply only the manufacturer-permitted additional partial turn with pliers	Tailpiece enters trap bend vertically with no visible gap at the washer
Trap arm to trap bend	Slip-joint nut and washer	Washer oriented per manufacturer instruction; trap arm square to the trap-bend outlet	Hand-tighten fully, then apply only the manufacturer-permitted additional partial turn with pliers	No side load on the trap bend; joint holds static pressure without weeping
Trap arm to wall adapter	Slip-joint nut and washer	Washer oriented per manufacturer instruction; trap arm reaches wall adapter without bending	Hand-tighten fully, then apply only the manufacturer-permitted additional partial turn with pliers	Joint holds static and full-flow drainage without leakage or movement

E. Acceptance Standards

Check	Standard
Alignment	Tailpiece enters the trap bend vertically; trap arm reaches the wall adapter without side load or forced bending
Trap seal and slope	Trap-seal depth and trap-arm slope match the original approved configuration recorded before removal
Slip-joint tightness	Every nut hand-tightened fully, then given only the manufacturer-permitted additional partial turn; no nut over-tightened to the point of cracking a washer
Static leak test	No visible leakage or weeping at any joint after the basin is filled and observed for the required period
Full-flow leak test	No leakage, siphoning, slow drainage, or cabinet contact observed when the full basin is released
Delayed reinspection	Dry-tissue check at every joint confirms a dry condition after the assembly has stood undisturbed

F. Identification and Documentation Review

1. Identify the sink type, drain size, tailpiece, trap adapter, wall connection, vent relationship, and approved replacement configuration. Record each item on the Sink Trap Assembly Worksheet before touching the existing assembly.
2. Protect the cabinet and floor and place a container beneath the trap. Confirm protection is in place before loosening any nut.
3. Confirm that no chemical drain cleaner or hazardous liquid is present. Treat any uncertainty as a stop-work condition until confirmed safe.
4. Photograph and measure the existing assembly before removal. Record tailpiece length, trap-arm length, wall-adapter height, and observed slope.

G. Removal and Inspection

1. Loosen the trap nuts while supporting the trap and controlling retained water. Direct retained water into the staged container.
2. Remove the trap bend and trap arm without damaging the wall adapter or tailpiece. Set removed components aside on protected material.
3. Clean the tailpiece and trap adapter sealing surfaces. Remove old washer residue, corrosion, and debris without damaging the sealing surface.
4. Inspect for corrosion, cracks, incorrect slope, double trapping, S-trap configuration, excessive extension, missing venting, or inaccessible wall damage. Record every condition observed, whether or not it stops work.
5. Stop work if the system requires concealed DWV correction or contains an unapproved configuration outside the chapter scope. Escalate to a qualified professional before installing a new trap on an unapproved configuration.

H. Dry-Fit and Alignment

1. Dry-fit the new trap bend, trap arm, nuts, and washers. Do not apply final tightening during the dry-fit.
2. Cut the trap arm square to the controlled length while preserving required insertion. Measure against the recorded original trap-arm length and adjust only as needed to reach the wall adapter correctly.
3. Orient each slip-joint washer correctly. Confirm the beveled or tapered face is positioned per the manufacturer instruction before final assembly.
4. Align the trap so the tailpiece enters vertically and the trap arm reaches the wall adapter without side load. Confirm no component is bent or forced to achieve alignment.
5. Maintain the approved trap-seal depth and trap-arm slope. Compare the dry-fit configuration against the original measurements recorded before removal.

I. Assembly and Tightening

1. Hand-tighten slip-joint nuts, then apply only the permitted additional tightening. Use slip-joint pliers for the final partial turn only, not for hand-tightening.
2. Do not use thread tape or pipe compound on slip-joint sealing surfaces unless the product instructions require it. Confirm the manufacturer instruction before applying any sealant.

J. Testing and Verification

1. Fill the sink and inspect the stopper or drain-body connection. Confirm no leakage at the drain body before proceeding to the trap test.
2. Release the full basin and observe the trap under high-flow drainage. Watch every joint during the full-flow release, not only after it completes.
3. Inspect every joint for leakage, movement, slow drainage, siphoning, and cabinet contact. Use dry tissue at each joint to confirm a dry condition.
4. Correct alignment or washer seating after draining the assembly. Depressurize by draining before loosening any joint for correction.
5. Repeat the fill-and-release test and perform a delayed dry-tissue reinspection. Allow the assembly to stand undisturbed before the delayed check.
6. Clean the work area and document the completed trap configuration. Complete every field on the Sink Trap Assembly Worksheet.