Plumbing During a Remodel: What to Replace While the Walls Are Open
By Mike Holt, NJ Master Plumber · April 12, 2024 · 3 min read · Updated November 1, 2026
Quick answer
A remodel is the cheapest time to fix old plumbing, because the walls and floors are already open. Replace old galvanized or corroded supply pipes, add shutoff valves at every fixture, check the drain and vent lines, and have the main sewer line camera-checked before new floors go in. Moving a sink, toilet or shower needs a plumbing permit in New Jersey.
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A kitchen or bathroom remodel opens up walls and floors that may not be opened again for decades. That makes it the cheapest moment to deal with old plumbing. A pipe you replace now costs a fraction of what it would cost after the new tile goes in.
What plumbing should you replace during a remodel?
| While the walls are open | Why it's worth doing now |
|---|---|
| Old galvanized steel supply pipes | They rust from the inside, lower water pressure and eventually leak |
| Corroded or patched copper | Green or white crust at fittings means slow leaks are coming |
| Shutoff valves at each fixture | Old valves seize; new quarter-turn valves let you stop a leak fast |
| Tub and shower valve | A new valve with anti-scald protection matches the new trim |
| Drain and vent lines | Cracked cast iron and bad slopes cause slow drains and sewer smells |
| The main sewer line | A camera check before new floors avoids tearing up a finished room |
If the house is older, ask about the main line too. A sewer camera inspection shows roots, cracks and sags before you put new flooring over the cleanout.
What changes when you move fixtures?
Keeping every fixture where it is costs the least. Moving one means rerouting both the water supply and the drain, and drains are the hard part. They need the right size, a steady downhill slope and a vent.
- Moving a sink a few feet is usually simple.
- Moving a shower or tub means a new drain location and a new valve.
- Moving a toilet is the biggest change. It needs a large drain line and a vent, and it may mean cutting into the floor and joists.
- Adding a bathroom or laundry room means tying into the existing drain and vent system, and sometimes a pump if it's below the sewer line.
Plan these moves with a plumber before you order fixtures, tile or cabinets.
Do you need a permit for remodel plumbing in NJ?
If you're adding, moving or replacing plumbing beyond a simple swap, yes. In New Jersey the town's construction office issues the permit under the Uniform Construction Code, and a licensed master plumber pulls it. Most remodels get a rough inspection with the walls open and a final inspection at the end. Our guide to NJ plumbing codes and permits covers the details.
When should the plumber come in?
- Before demolition, for a walkthrough: what stays, what moves and what's worth replacing.
- After demolition and framing, for rough-in: new supply, drain and vent lines, then the rough inspection.
- After tile and cabinets, to set fixtures: toilet, sink, faucets and shower trim, then the final inspection.
Build the plumbing inspections into your contractor's schedule early, so the job doesn't stall with the walls open.
Is it time to repipe the whole house?
If your remodel turns up galvanized steel, or you already have low pressure and rusty water, the rest of the house probably has the same pipe. Repiping while one room is open can be a good time to start. See signs your home needs repiping and our repiping service. Contact us to confirm whether we handle your scope and materials.
Plumbing Doctor handles remodel plumbing across Central New Jersey, from rough-in to setting fixtures, under NJ Master Plumber Lic. #36BI01345600. We don't remove or install undermount sinks, so tell us early if your plan includes one. Written upfront flat-rate pricing options. You choose. Most company-supplied materials and repairs come with a 1 year parts and labor warranty. Client-supplied materials are not covered under our warranty. Call 908-873-6686 to walk through your remodel with us.
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Stop and call us if
- Your plan moves a toilet, tub, shower or sink to a new spot.
- You find galvanized steel, lead or badly corroded pipes behind the walls.
- The house has had slow drains or sewer backups.
- You're adding a bathroom, a laundry room or a gas range.
Call 908-873-6686.
Michael Holt
Owner and operator of Plumbing Doctor, NJ Master Plumber (Lic. #36BI01345600) and U.S. Marine Corps veteran.
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