Quick Answer: Rough-in plumbing for a new bathroom in San Jose costs $3,500–$8,000 when the new bathroom is close (within 10 feet) to an existing drain stack, and $7,000–$15,000 when the stack is far away or requires opening the slab or crawlspace. This includes drain lines, supply lines, vent stack connections, and the plumbing permit. Plumbing is typically 25–35% of the total bathroom addition cost.
Rough-In Plumbing Cost by Bathroom Location — San Jose 2025
Helpful Resources:
| Bathroom Location | Distance to Stack | Rough-In Cost Range |
|---|---|---|
| Sharing wall with existing bath or kitchen | 0–5 ft | $2,500–$5,000 |
| Adjacent room, same floor | 5–15 ft | $4,000–$8,000 |
| Opposite side of house, same floor | 15–40 ft | $7,000–$13,000 |
| New addition (off the back of house) | New line to street | $8,000–$18,000 |
| Second floor above existing first-floor bath | Stacked plumbing | $3,500–$7,000 |
What Is Included in Bathroom Rough-In Plumbing?
- Drain lines: ABS or PVC drain lines for toilet (3″ or 4″ pipe), sink (1.5″), and shower/tub (2″)
- Vent stack connection: Extending or connecting to the existing vent stack to prevent sewer gas backup
- Supply lines: Hot and cold water supply lines (typically 1/2″ copper or PEX) to sink, toilet, and shower
- Cleanout installation: Accessible cleanout fitting required by California Plumbing Code
- Pressure testing: Pressure test before walls are closed, required for plumbing inspection
- Permit and inspection: San Jose plumbing permit + rough-in inspection by the city
Slab vs. Raised Foundation — How Foundation Type Affects Plumbing Cost
Homes on raised foundations (crawlspace) in San Jose are significantly easier and cheaper to rough-in than slab homes. On a raised foundation, plumbers access drain lines from the crawlspace without cutting concrete. On a slab home, adding new drain lines requires cutting and jackhammering the concrete slab — adding $2,000–$6,000 to the project cost.
Frequently Asked Questions
How long does rough-in plumbing take for a new bathroom in San Jose? Plumbing rough-in typically takes 2–4 days for a single bathroom. The plumbing permit inspection adds 1–2 weeks depending on San Jose Building Division inspection scheduling.
Do I need a plumbing permit to add a bathroom in San Jose? Yes — all new bathroom plumbing in San Jose requires a plumbing permit from the City of San Jose Building Division. The permit covers drain lines, supply lines, vent stack modifications, and requires a rough-in inspection before walls can be closed.
What is PEX pipe and should I use it for my San Jose bathroom addition? PEX (cross-linked polyethylene) is a flexible plastic pipe widely used for supply lines in Bay Area bathroom additions. It’s faster to install than copper, resistant to freezing, and approved under California Plumbing Code. Quartz Construction uses PEX for supply lines and ABS or PVC for drain lines on bathroom addition projects.
Quartz Construction & Remodeling (CSLB #1003436) handles all bathroom plumbing work in San Jose and throughout the Bay Area. Call (650) 749-7436 for a free bathroom addition consultation and plumbing rough-in estimate.
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