The wall you cannot reopen
Picture the day after tile goes up. The shower valve sits two inches too low for the new head, and nobody noticed until the finished wall was in front of you. Fixing it means breaking the tile you just paid to install.
That scenario is why a bathroom remodel starts on paper. The studs are open only once, and the plumber needs your answers while they are. If you want to talk a layout through, call (206) 864-6558 and describe what you plan to keep and what you plan to move.
Decisions in the order the work happens
Settle these in sequence, because each one limits the next.
Pick the fixtures
Toilet, vanity, tub or shower valve, and faucet models set the rough-in dimensions the plumber works to.
Fix the layout
Decide which fixtures stay where they are and which move. Every move adds work to drain, vent and supply.
Plan the drain route
The toilet and shower drains need a steady pitch to the main stack, and that can dictate where fixtures end up.
Set valve heights
Shower valve, handheld holder and showerhead positions all need to match your height and your tile pattern.
Test and inspect before closing
Pressure-test the supply lines and look at every joint before the drywall covers them.
Describe the new layout to our dispatcher at (206) 864-6558, and we will say what it asks of the pipes.
Rough-in items and why they lock in
| Item | What to decide | Why it cannot wait |
|---|---|---|
| Toilet flange | Center distance from the back wall and from side walls | The flange sits in the floor, and moving it means cutting the subfloor |
| Shower valve | Model, height and trim style | The valve body is set in the wall and the trim must match its depth |
| Vanity supply and drain | Single or double sink, plus faucet type | Stops and drain stub-outs live inside the wall behind the vanity |
| Tub or shower drain | Footprint, drain position and pan type | The drain connects below the floor, so the pan must fit it |
| Vent path | Where the vent rises and joins the stack | A vent needs a route up through the wall or the attic |
| Shutoff valves | Fixture stops, plus an accessible main for the bathroom | A stop that is tiled over is a flood waiting for a bad day |
Shower, tub or both: the plumbing difference
A walk-in shower needs a drain in the floor, a waterproof pan beneath the tile and a valve with the right trim depth. A tub needs an overflow, a drain assembly and access to the trap, often from below or through a panel on the far side of the wall.
A tub-to-shower conversion keeps some of those lines and changes others. The existing drain may sit in the wrong place for a larger shower base, and the floor under the tub often needs repair once the tub is out.
If you plan a body spray or a second showerhead, say so early. Extra outlets draw more water at once, and the supply lines and the valve must be sized to feed them without starving the main head.
Drain pitch and venting, in plain words
A drain line carries waste by gravity. It needs a gentle, steady downhill pitch. Too flat and solids sit and clog. Too steep and water outruns the solids and leaves them behind. The code sets the allowable pitch, and the plumber lays out the pipe to it.
A vent lets air behind the water so it flows without suction. Each fixture trap holds a seal of water against sewer gas, and a poor vent can pull that seal dry. If you are adding a fixture, ask where its vent will rise and whether it joins an existing stack.
A larger layout change can mean new lines through the floor or ceiling. That is where plumbing installation work moves from a fixture swap to a small project.
Questions to settle before demo day
- Where is the main shutoff? Know it, test it and label it before any wall is opened.
- What pipe material is in the walls? Galvanized steel, copper, PEX and cast iron all behave differently when cut into.
- Is the toilet drain moving? If so, confirm the new path and the pitch before ordering a vanity.
- Do the fixtures match the rough-in? Fixture models should be on site, not just ordered.
- Which stages get inspected? Ask the city permit center if the work needs a permit, then plan the schedule around inspection.
- Who covers hidden damage? Decide in advance what happens if the open wall shows rot or a failed pipe.
Old pipes show up at demo
Late 1940s and 1950s homes commonly had galvanized steel supply lines and cast iron or clay drains. Many have been partly replaced with copper or PEX since. Newer builds from the 2000s onward often use PEX.
A camera inspection and a pipe-material check before you commit will show what is in your walls. If the supply lines are old, the remodel is a good moment to talk about repiping the bathroom run while the wall is open.
When the work should stop
Pause the job and call if demo exposes a leaking joint, a corroded supply line or a drain that is cracked or sagging. Pause if you find water near a wet electrical box, and do not touch it.
If anyone smells gas during the work, leave the building and call the gas utility or 911 first, then call us. We do not service gas lines. Our line takes remodel questions too, and we also cover Lynnwood bathroom projects next door.
What this means in Mountlake Terrace
Washington adopts the 2021 edition of the Uniform Plumbing Code, published by IAPMO, with state amendments. For you, that means the layout of drains, vents and traps in your bathroom is set by a published standard and not by taste. Ask any plumber how they handle that standard and what gets inspected, and we are glad to answer the same questions.
The city also keeps a permit center at City Hall, 23204 58th Ave W, with building, electrical, mechanical and plumbing permit types. Permit rules vary, so ask the city permit center before the work starts, at 425-776-1161.
The first Mountlake Terrace houses were compact postwar cinderblock homes, and many were renovated and expanded over the decades. If your bathroom is in an older or expanded house, the plumbing behind the wall may be a mix of old and newer work. Plan for surprises, and ask for a pipe-material check during demo.
Remodel questions worth settling early
Usually yes, but it is the most consequential choice in the remodel. The toilet drain is the largest line, and it needs a downhill path to the main drain. Moving a shower is easier, though the drain still needs pitch and a vent.
A vent lets air into the drain system so water flows freely and the P-trap seals do not get sucked dry. Without it you get gurgling, slow drains and sewer gas. Every fixture needs a vent path, and the plumber lays it out during rough-in.
Almost always. Old supply stops and shower valves are cheap to change while the wall is open and costly to reach later. New fixtures also work better with new stops, so you can shut off a single fixture without losing water to the house.
You can ask, but a remodel is the owner's project, and the owner must approve any pipe changes. If a plumbing problem is what you want fixed, report it to the landlord or property manager. We can talk to them about what we find.
Permit rules vary, so ask the city permit center before the work starts. The center is at City Hall, 23204 58th Ave W, 425-776-1161. Ask your plumber to explain which stages of the job get inspected before you cover them.
Your fixture choices. A plumber needs the actual toilet, vanity, tub or shower valve model, because rough-in dimensions come from the fixture. If the choice changes later, the pipes in the wall may need moving.
Standards and sources
These public references sit behind the rules and checks this page mentions.