Moving a sink a few feet is cheap. Moving a toilet across the room is not. That one fact explains most of the spread in bathroom plumbing cost, and it’s the first thing we check on a Renton remodel. Here is what it costs to move fixtures, what a full rough-in runs, and when the house itself makes the job easy or hard.
All prices below are estimates from 2026 national cost guides and our own jobs. Your quote depends on your house.
Bathroom plumbing cost at a glance
| Job | Estimated cost |
|---|---|
| Shift a sink along the same wall | $500 – $1,200 |
| Move a sink to a new wall | $1,000 – $3,000 |
| Move a toilet a few feet (toward the stack) | $500 – $1,500 |
| Move a toilet across the room | $2,500 – $5,000 |
| Relocate a shower or tub drain | $1,000 – $3,000 |
| Full rough-in for one bathroom (new supply, drain and vent lines) | $3,000 – $20,000 (avg about $6,500) |
| Extra for cutting a concrete slab | $1,000 – $3,000+ |
| New water line, per line | $80 – $200 |
| Plumber hourly rate | $80 – $130 (range $45 – $200) |
| Plumbing permit | $30 – $500 |
Plumbing is the second-biggest line in most bathroom remodels after tile. Keep the fixtures where they are and it’s a few hundred dollars per connection. Move them and you’re paying for new drain lines, new vents, framing cuts, and the finish work to close it all back up.
Why moving a toilet costs more than moving a sink
Each fixture has a different drain.
A sink uses a small 1½-inch drain and flexible supply lines. A plumber can usually shift it inside the same wall in a morning.
A shower or tub needs a 2-inch drain and a floor that slopes to it. Moving the drain means opening the floor and sometimes re-framing joists.
A toilet needs a 3-inch drain that slopes a quarter inch for every foot it runs, plus a vent. The farther it moves from the main stack, the more floor comes out. That’s why the same job can be $500 or $5,000.
The other big factor is where the fixtures sit relative to the main waste stack. Fixtures on the stack wall are cheap to move. Fixtures on the far wall are not.
Crawlspace or slab? In Renton, this is the whole game
Most older Renton homes, the 1960s and 70s ramblers in the Highlands, Benson Hill and the Cascade area, sit on a crawlspace. That’s good news. A plumber can get under the floor, re-route drains and run new supply lines without tearing up the finished floor. Costs stay in the lower half of the ranges above.
Newer homes and some split-levels have a slab or a finished lower floor under the bathroom. Then every drain move means cutting concrete, re-routing the line, and pouring it back. Plan on $1,000 to $3,000 on top of the plumbing itself.
One more Renton reality: many homes built before 1980 still have galvanized steel supply lines. Once we open a wall, we often find corroded pipe with half its flow gone. Swapping the bathroom’s supply lines to PEX while the wall is open runs roughly $1.50 to $4 per foot in material plus labor, and it’s the cheapest moment you’ll ever have to do it.
What a full rough-in includes
If you’re gutting the bathroom and changing the layout, you’re paying for a rough-in, not a fixture swap. That covers:
- New drain and waste lines to each fixture
- Vent lines up through the roof or tied into an existing vent
- Hot and cold supply lines, usually PEX
- Shutoff valves at every fixture
- The shower valve body and tub spout drop
- A pressure test and the rough-in inspection before walls close
National guides put a one-bathroom rough-in at about $3,000 to $20,000, with most landing around $6,500. In Renton, crawlspace homes with the bathroom near the stack land low. Slab homes with a full layout flip land high.
Permits in Renton
The City of Renton says separate permits are required for electrical, plumbing and mechanical work, on top of any building permit for the remodel itself. The good news: plumbing permits are over-the-counter permits you apply for online, and same-day approval is typical.
A simple like-for-like fixture swap is usually not a permit job. Moving a drain, adding a vent, or running new supply lines is. Your contractor pulls the permit, schedules the rough-in inspection (the city books them for the next business day), and the walls stay open until it passes.
If your home is on a septic system and you’re adding fixtures, Renton requires approval from King County Environmental Health first. That’s rare inside city limits but common on the edges toward Maple Valley.
Half bath to full bath: a special case
Turning a powder room into a full bath is one of the most common plumbing-heavy requests we get. You’re adding a 2-inch shower drain, a new vent, and often stealing space from a closet. The plumbing alone usually runs $3,000 to $8,000 in our estimates, before tile, waterproofing and fixtures. If the powder room shares a wall with an existing bathroom, the cost drops because you can tie into that stack.
If you’re adding a bathroom where none exists, that’s a different project with a different budget. See our guide to adding a bathroom to your home.
Ways to keep the plumbing bill down
- Keep the toilet where it is. Move everything else first. The toilet is the expensive one.
- Stay on the wet wall. Line up the sink, toilet and shower on the wall with the stack.
- Move the sink, not the drain. A wider vanity or a double sink can often reuse the existing drain with a wider trap arm.
- Do it with the floor open anyway. If you’re replacing tile or installing a heated floor, the floor is already out. Moving a drain then costs far less.
- Replace old valves and supply lines now. It adds a little and saves a flood later.
What’s not in the plumbing number
Plumbing quotes rarely include the work around them. Budget separately for drywall and tile repair where lines were run, flooring patches, the fixtures themselves (a toilet, vanity or shower valve is priced on its own), electrical if a new outlet or fan goes in, and demolition if the room is being gutted. For the full picture, our Renton bathroom remodeling page covers the whole project.
Frequently asked questions
How much does it cost to move plumbing in a bathroom?
Shifting a sink along the same wall runs about $500 to $1,200. Moving a toilet a few feet is $500 to $1,500; across the room it’s $2,500 to $5,000. Relocating a shower drain is $1,000 to $3,000. These are 2026 estimates and depend on whether the house is on a crawlspace or a slab.
What is the cost to rough in plumbing for a bathroom?
A full rough-in for one bathroom is roughly $3,000 to $20,000, with a national average around $6,500. Layout changes, slab foundations and distance from the main stack push it up.
Do I need a permit to move bathroom plumbing in Renton?
Yes. Renton requires a separate plumbing permit for moving drains, adding vents or running new supply lines. It’s an over-the-counter permit applied for online, and the rough-in has to be inspected before the walls close. Swapping a fixture in the same spot usually does not need one.
Is it cheaper to move plumbing in a crawlspace home?
Usually, yes. A plumber can reach the lines from below without cutting the floor. On a slab, cutting and re-pouring concrete adds $1,000 to $3,000 or more.
How much does it cost to convert a half bath to a full bath?
The plumbing portion typically runs $3,000 to $8,000 in our estimates, before tile, waterproofing and fixtures. It’s cheaper if the half bath backs up to an existing bathroom’s stack.
Get a straight quote
If you’re changing your bathroom layout in Renton, Kent, Newcastle or anywhere in South King County, we’ll crawl under the house, find the stack, and tell you what the move really costs before you commit. Call us at 206-851-4233 or contact us here. Our Renton office is on SW 16th Street.
Estimates only. Actual costs depend on your home’s plumbing, foundation and layout.
