When should the plumber be involved in a remodel?

Design decisions are plumbing decisions. Every fixture on your plan is a supply line, a drain and a vent, and where those go decides how much work the job turns into. A plumber looking at your drawings can flag problems while they still cost you an eraser instead of a demolition crew.

Here is what a plumber checks before you lock a layout.

• Does a fixture move? A toilet, sink, tub, shower, dishwasher or kitchen sink that stays put usually reuses the existing pipes. One that moves means new drain and vent runs, and drains need slope to work. Our page on drain pipe slope shows why you can't just slide a drain wherever the layout looks nice.
• What is the floor made of? In a lot of Phoenix homes, drain lines run in or under a concrete slab. Moving a toilet or shower on a slab can mean cutting the concrete. On a raised floor, the plumber checks the joists instead.
• Where do the pipes run now? Before demolition, it helps to know what's in the walls. Our guide on how to find where water pipes run covers what you can figure out yourself, and a plumber can confirm the rest once the wall is open.
• What's the pipe condition? If the existing supply lines are old or failing, a remodel is the cheapest moment to replace them, because the walls are already open. See signs of old failing pipes and PEX vs CPVC if you're weighing replacement options.
• Do the new fixtures fit the system? A big soaking tub, a body-spray shower or a pot filler can ask more of your water heater, supply pipes and pressure than the old setup did. Whole-house pressure is worth knowing before you buy. Our page on what home water pressure should be explains the range.
• Which fixtures are you buying? Have the actual fixture spec sheets in hand. Rough-in dimensions, valve types and drain sizes differ by model, and the plumber sets pipes to match the fixture you chose. EPA's WaterSense program, for example, says its labeled showerheads must demonstrate that they use no more than 2.0 gpm, and its labeled toilets use 1.28 gallons per flush or less. Those are useful things to know when you pick fixtures, and worth mentioning to the plumber.

### Bathroom versus kitchen

Bathrooms pack the most plumbing into the least space, so the plumber matters early. Moving the toilet, converting a tub to a shower, or adding a second sink all change the drain layout. The shower valve and any body sprays are set inside the wall, so the plumber needs the exact valve model and the tile plan before rough-in.

Kitchens look simpler, but they hide surprises. A sink move, an island sink, a pot filler over the range, a new dishwasher location or a filtration system each need water and drain in a specific place. A sink on an island also needs a vent path, which is easy to overlook in a drawing. Gas ranges and gas lines are a different category: they need a licensed professional and a permit, so bring that up at the design stage too.

That's the design-stage takeaway. Get the plumber's eyes on the plan, and get their yes or no on any fixture that moves.

Rough-in is the stage where the plumber installs the pipes inside the open walls and floors, before anything covers them. Supply lines, drains, vents and the shower or tub valve all get set here, sized to the fixtures you picked.

The plumber has to be in before the drywall and tile crews because those trades cover the pipes. Here is the usual order of a remodel, with the plumber's steps marked.

1. 1Design and permits. Plumber reviews the plan and, if the job needs it, the permit gets pulled.
2. 2Demolition. Old fixtures and finishes come out. Now everyone can see what's actually in the walls and floors.
3. 3Framing changes. Any new walls, niches or reframing happen here. Plumbing goes in around the framing, so the plumber needs to be told about changes before they're built.
4. 4Plumbing rough-in. New and moved pipes, valves and vents go in.
5. 5Pressure test and rough-in inspection. The lines are tested while the walls are still open (more below).
6. 6Insulation, drywall, waterproofing, tile. The walls close, and the finishes go on.
7. 7Cabinets and countertops. Kitchen cabinets and counters go in, so sink cutouts must match the plan.
8. 8Trim-out. The plumber sets the fixtures, faucets, toilets and connects everything.
9. 9Final inspection and sign-off.

Two timing points catch people out.

Rough-in comes before waterproofing and tile. A shower valve has to be set at the right depth for the tile you picked. If the tile crew shows up and the valve is too deep or too shallow, somebody is opening a wall. Confirm the valve depth and the tile thickness together before the walls close.

Rough-in also depends on the cabinet plan. In a kitchen, the supply stubs and drain need to land inside the sink base cabinet. If the cabinet order changes after rough-in, the pipes may need to move. Give the plumber the final cabinet layout, not the first draft.

Because this is the only time you can see the pipes. Plumbing that's leaking or draining wrong shows up best when the wall is open, and it's cheap to fix right then.

After the plumber roughs in the pipes, the system gets tested to find leaks and defects before it's covered. The model International Plumbing Code says that plumbing work and systems are tested by the permit holder and observed by the code official, and that new plumbing systems and parts of existing systems that have been altered, extended or repaired must be tested to disclose leaks and defects. Then the inspector checks the work.

Here is how the inspection stages work in the model code. The International Plumbing Code says the rough-in inspection is made after the framing and bracing are in place and all sanitary, storm and water distribution piping is roughed in, and before the installation of wall or ceiling membranes. It says the final inspection is made after the building is complete and all plumbing fixtures are in place and properly connected. It also says that work shall not be done beyond the point indicated in each successive inspection without first obtaining the approval of the code official.

In everyday terms: you don't close the walls until the inspector has signed off on the open pipes.

The same code says construction or work for which a permit is required shall remain visible and able to be accessed for inspection purposes until approved. That's why a contractor who hangs drywall before an inspection can cause real trouble.

One caution. Those quotes come from the model code, published by the International Code Council. The City of Phoenix adopts its own building codes and local amendments, and its building code page lists both the 2024 International Plumbing Code and the 2024 Uniform Plumbing Code among the codes it adopted. Exactly which inspections apply to your job, and how you schedule them, is set by the city. Confirm the details with the City of Phoenix Planning and Development Department before work starts.

### Do you need a permit?

It depends on the work. The City of Phoenix Work Exempt from Permit sheet says a plumbing permit isn't required for the replacement of water closets, valves or fixtures with new valves or fixtures complying with the conservation requirements of the code, but that a permit is required for the relocation of any valves, pipes or fixtures. Exempt work still has to meet code.

So a like-for-like swap may not need a permit, and a remodel that moves pipes does. Our pages on permits for a bathroom remodel in Phoenix and what plumbing work needs a permit in Phoenix go deeper, and plumbing permit timelines cover what to expect. Check your specific scope with the city, because permits and inspections are the part where guessing gets expensive.

It's a familiar pattern. The design is done, the cabinets are ordered, the drywall is up, the tile is in, and then somebody realizes the plumber was never scheduled. Here is what that usually looks like.

• The walls are already closed. The plumber can't reach the pipes, so the only options are cutting into finished surfaces or working around what's there. Every option costs time and repairs.
• The layout doesn't work. The sink base is in the wrong place, or a fixture sits where a drain can't reach with proper slope or venting. Now the layout has to change, or the plumbing gets compromised.
• The valve doesn't fit the tile. The shower valve is set for the wrong wall thickness and the trim doesn't seat, so the tile has to come off.
• The inspection fails or can't happen. The model code puts it on the permit applicant to keep the work visible and accessible, and says neither the code official nor the jurisdiction is liable for expenses entailed in the removal or replacement of any material required to allow inspection. That expense lands on you. Work that fails an inspection has to be corrected and resubmitted.
• Hidden problems show up late. A leaking joint that would've been obvious under a rough-in test turns into a stain, mold or a damaged cabinet months later. Our guide on how plumbers find hidden leaks and the page on a leaking shower valve behind the wall show how much work it takes to find one after the fact.
• The schedule slips. Every other trade waits while the plumbing gets sorted out.

Late is fixable. Every one of these is cheaper to avoid than to repair.

Some plumbing work is fine to do yourself. Painting, caulking, swapping a faucet in the same spot, replacing a toilet on the existing flange and installing a new vanity on the existing pipes are typical like-for-like jobs. Even so, exempt doesn't mean unregulated. The city's Work Exempt from Permit sheet says that even when work is exempt, it must still comply with the code and the owner is responsible for proper and safe construction.

Call a licensed plumber when the job involves any of these:

• Moving or adding a fixture, or changing drains, vents or supply lines.
• Cutting into a slab to reach drain lines.
• Replacing old supply piping while the walls are open.
• Anything that needs a permit or inspection.
• Gas lines and gas appliances, which need a licensed professional and a permit.
• Work you can't easily reach again once the walls are closed.

If you aren't sure, ask the plumber to walk the job before demolition. It's a short visit that tells you what's inside the walls. Our pages on licensed contractors versus handymen in Arizona explain who's allowed to do what.

### What to ask a plumber before a remodel

Bring these to the first walkthrough.

1. 1Can you review my plans before I finalize the layout?
2. 2Which fixtures are moving, and what does each move require (drains, vents, supply)?
3. 3Is my floor a slab or raised, and does that change the plan?
4. 4What's the condition of my existing pipes, and should they be replaced while the walls are open?
5. 5Who pulls the permit, and which inspections will the job need?
6. 6When exactly do you need to be on site relative to the framing, drywall and tile crews?
7. 7What do you need from me before rough-in (fixture spec sheets, valve models, cabinet layout, tile thickness)?
8. 8How will you test the lines before the walls close, and can I see the result?
9. 9Who schedules the inspections, and what happens if one fails?
10. 10When do you return for trim-out, and what does the final inspection cover?

A good plumber has answers ready. If you get vague ones, that's information too.

### The timeline in one glance

Call the plumber at design, again at rough-in, again at the test and inspection, and once more at trim-out and final. Four touchpoints, all before you're done. Skip the early ones and the last one gets much harder.

HQ Plumbing & Air is licensed and insured, and we give upfront pricing and free estimates. If you're planning a remodel, call us before the design is set. Our team is available 24/7 if something goes wrong at any stage.