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Bathroom remodel plumbing in San Jose, from rough-in to final fixtures
Moving a toilet, splitting one sink into two, adding a bathroom to an ADU or upstairs. The finish work gets the attention, but the drain slope, venting and supply behind the walls decide whether the new bathroom works.
Bathroom remodel plumbing in San Jose is the rough-in behind the walls and floor, meaning drains at the right slope, vents and new supply lines, followed by an inspection before the walls close and fixture setting after tile. Moving a toilet or adding a bathroom changes the drain layout, so it is planned first.
The job
What the plumber decides before the tile is picked
Every fixture needs a drain big enough, sloped correctly and vented within the distance code allows. Keeping fixtures where they are is simple. Moving them means rerouting drains through joists or a slab, and that can cost more than the fixtures, so we walk the layout with you or your contractor before anything is ordered.
Open walls are also the cheapest time to fix what is behind them: old galvanized supply, a cracked cast iron stack, stops that no longer close. If the whole house is on old pipe, a remodel is a good moment to plan whole-house repiping. A new tub is covered under bathtub installation.
Cost factors
What moves the price of remodel plumbing
- Fixtures that move Keeping the layout is cheapest; moves reroute drains.
- Slab or raised floor Cutting concrete costs more than working between joists.
- Pipe found in the walls Old galvanized or cast iron may be worth replacing now.
- Venting A new vent through the roof adds labor.
- Fixture choices Wall-mounted faucets and custom valves need exact rough-in.
Every job is priced after we see it; any published range is for planning only.
Relocating a toilet
A toilet needs a 3 inch drain, a vent, and a flange set at the right distance from the finished wall. On a raised foundation, moving it a few feet usually means cutting a new hole and running drain between joists, which is straightforward when the joists run the right way. On a slab, the concrete is cut, the new drain trenched at the correct slope and the slab patched. We confirm the path before demolition, because a toilet moved against the joist direction can need structural work.
Double vanity rough-in
Two sinks need two drains or a correctly sized shared one, two sets of supply stubs, and a vent arrangement that keeps both traps from siphoning. We set the stub-out heights to the vanity you have picked, not a generic number, and center them on the bowls so the cabinet does not need creative carpentry. Wall-mounted faucets need their valves roughed into the wall at the exact height, which is why we ask for the faucet model before the drywall goes up. See our faucet installation page for trim-out.
Primary bath expansion
Enlarging a primary bathroom, often by taking space from a closet or the bedroom next to it, usually means moving the toilet, the shower drain or both, and adding a second sink. Each moved fixture needs its own drain at the right slope and a vent, and on a slab the concrete is cut along the new routes. We lay out the new positions from the design, confirm the drain and vent paths before demolition goes too far, and pressure-test the new supply lines before the walls close.
Second-floor bathroom drain
An upstairs bathroom sends its drain down through the house to the main stack or a new one, and the path has to keep slope without cutting joists beyond what code allows. We plan the route with the framer, protect the drain lines with nail plates, and pressure or water test the whole system before the ceiling below closes. A leak found now costs a coupling; found after drywall and paint, it costs a ceiling. Shower pans upstairs get a flood test before tile goes on.
What is included
What remodel plumbing includes
- Layout review with you or the contractor
- Plumbing permit for the altered work
- Drains sized and sloped to code
- Vents for every new trap
- New supply lines and stops
- Valve rough-in at the finished height
- Water or pressure test before walls close
- Rough-in inspection
- Fixture setting after tile
What happens after you call
How a remodel job runs with us
- 1
Walk the layout
Fixtures, drains and vents planned before ordering.
- 2
Permit
Pulled for the altered plumbing.
- 3
Rough-in
Drains, vents and supply to your fixtures.
- 4
Test and inspect
Tested, then inspected before walls close.
- 5
Tile and finish
Your contractor closes up and tiles.
- 6
Set fixtures
Toilet, faucets and trim installed and tested.
Local context
Cast iron stacks behind San Jose bathroom walls
Many San Jose homes built before 1975 still drain through cast iron hub-and-spigot stacks, and that pipe corrodes from the inside and the outside, failing at roughly 50 to 65 years. A remodel is often the first time anyone has seen it. When the walls come open, we look at the stack and the horizontal runs, and if they are thin or cracked we price the section in the open wall, because closing tile over a failing stack means opening it again.
Timing
How long the bathroom is out of service
A like-for-like layout is the short end of the range. Moves through a slab, an added vent to the roof, or an upstairs drain take longer, and the schedule also waits on the city inspection before walls close. If it is your only bathroom, tell us early: we plan the order so a toilet stays usable as long as possible.
Brands we service and install
FAQ
Remodel questions we hear before demolition
Only where a 3 inch drain can reach the stack at proper slope and be vented.
Yes, when drains, vents or supply lines are altered.
Yes. We rough in to the plans and coordinate on schedule.
Usually. It is the cheapest time to do it.
Kohler, Toto, American Standard, Moen, Delta and most others.
Yes; a whole ADU is covered on our ADU plumbing page, including the sewer tie-in.
The drain route takes planning, and everything is tested before ceilings close.
Related work
Other Kitchen & Bath jobs we handle
Plan the plumbing before the tile
Call any hour to book a layout walk-through in San Jose.
Updated September 2026