Quick Answer: Plumbing rough-in cost in San Jose ranges from $2,500-$8,000 for a single bathroom or kitchen addition, and $15,000-$35,000 for a full ADU or new construction plumbing rough-in. “Rough-in” refers to installing the supply (water) lines and drain/waste/vent (DWV) pipes before walls are closed — the portion of plumbing work that runs through floors, walls, and ceilings during the framing stage. The biggest cost factors are: distance from existing plumbing stacks (longer runs = more pipe, more labor), the number of fixtures (toilet, sink, shower = 3 fixture units vs. a kitchen with sink only = 1), and whether the slab must be cut for new drains (costly — $2,000-$6,000 per cut).
Plumbing Rough-In Cost by Project Type — San Jose 2025
| Project | Rough-In Cost Range | Notes |
|---|---|---|
| Half bath addition (toilet + sink) | $2,500 – $5,500 | Near existing stack: lower end; remote location: higher |
| Full bathroom addition (shower/tub + toilet + sink) | $4,000 – $9,000 | Includes DWV and supply for 3 fixtures |
| Kitchen addition (sink + dishwasher + disposal) | $2,000 – $5,000 | Gas line for range not included |
| Garage conversion ADU (full plumbing) | $12,000 – $22,000 | Full kitchen + bath rough-in; often requires slab core drill for drains |
| Detached ADU (new construction plumbing) | $18,000 – $35,000 | Service connection from street + full interior rough-in |
| Slab penetration / core drill | $1,500 – $4,500 per location | Required when adding drains through concrete slab floor |
| Relocating kitchen sink (within same room) | $1,500 – $4,000 | Moving drain and supply lines; permit required in San Jose |
Quartz Construction coordinates all licensed plumbing subcontractors for San Jose renovation, addition, and ADU projects. All plumbing work is permitted and inspected through the San Jose Building Department. CSLB #1003436 | Call (650) 749-7436.
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Quartz Construction & Remodeling | CSLB #1003436 | Licensed, Bonded & Insured
Phone: (650) 749-7436
Address: 1777 Hamilton Ave #1080, San Jose, CA 95125
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