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New construction plumbing: the stages, inspections and who to hire

Building a home, an addition or a commercial space? Plumbing goes in at fixed stages, and the building department inspects each one before anything is covered up.

The short answer

New construction plumbing is installed in stages: underground (pipes below the slab or in trenches), rough-in (drain, waste, vent and supply pipes inside walls and floors), top-out on many jobs, and final (fixtures set and working). The building department inspects each stage before it is covered, usually with a water or pressure test. In most places a licensed plumber pulls the permit – plan for that when you choose who to hire.

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The stages, in order

  1. Underground / groundwork. Pipes in trenches or under the slab, before backfill or the pour. Augusta, Georgia calls for this inspection after trenches are dug and piping is installed, before any backfill, with a pressure test; Henrico County, Virginia requires underground piping to be leak-tested during its groundwork inspection.
  2. Rough-in. Drain, waste and vent piping and water supply lines run through the framing, before walls and ceilings close. Rio Rancho, New Mexico requires the rough-in inspection after all piping is installed and before any of it is covered.
  3. Top-out. Many departments, such as Rio Rancho, inspect again once piping above the floor, up through the roof and walls, is complete. Las Cruces, New Mexico water-tests built-in shower pans at this stage.
  4. Final. Fixtures installed and ready for service. Henrico County’s final inspection checks that every fixture works and every drain is connected; Augusta calls it once the building is ready for occupancy.

The tests inspectors look for

Inspections are not just a look. Las Cruces requires drain, waste and vent piping at rough-in to be filled with water to at least a 10-foot head; Henrico County requires supply piping to be pressure tested for leaks. A failed test means the plumber fixes it and the inspector comes back – another reason to keep the schedule realistic.

Permits: who pulls them

Plumbing in new construction needs a permit. University City, Missouri requires permits and inspections for all new plumbing installations, major repairs and modifications. Who may pull the permit is set locally: University City issues plumbing permits to master plumbers or drainlayers licensed by St. Louis County, with only a limited homeowner option for existing single-family homes, and the City of St. Louis issues them to licensed plumbing contractors certified by the city. Ask your building department before you sign a contract – and check the license on your state’s official lookup.

Hiring a plumber for a new build

  • Bid on drawings. Give every plumber the same plans and fixture list so the quotes compare.
  • Ask who pulls the permit and who schedules each inspection.
  • Ask how stages are billed – many contracts tie payments to passed inspections.
  • Coordinate with other trades. Rough-in has to happen after framing and before insulation and drywall.
  • Confirm the license and insurance, and ask for the warranty on labor and materials in writing. Our hiring guide has the full question list.

Building water-efficient

EPA says WaterSense labeled new homes are 30 percent more water-efficient than typical new construction; they include WaterSense labeled fixtures and must be free from leaks. New construction is the cheapest moment to plan fixture choices, hot-water routing and a water heater type.

Are you a plumber who does new construction?

Builders and owners use this directory to find plumbers. If you do new-construction or commercial work, make sure your listing says so – it is free.

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Questions

What are the stages of new construction plumbing?

Typically underground (below the slab or in trenches), rough-in (pipes inside walls and floors), top-out on many jobs, and final (fixtures set). Each stage is inspected before it is covered.

What is a plumbing rough-in inspection?

An inspection of the drain, waste, vent and supply piping after it is installed and before walls, floors or ceilings cover it, usually with a water or pressure test.

Can a homeowner pull a plumbing permit for new construction?

It depends on the city or county. Many issue plumbing permits only to licensed plumbers; some allow limited homeowner permits for existing single-family homes. Ask your building department.

How do I find a plumber for a new build?

Use the city pages in this directory, filter for commercial or new work where shown, and send the same plans to two or three plumbers for written bids. You can also request a plumber here.

Related guides

Bathroom and kitchen remodel plumbing: permits, pipes and fixturesA remodel is the best chance to fix what is inside the walls. Here is when the plumbing needs a permit, which old pipes are worth replacing, and how to choose fixtures.Commercial plumbing: codes, grease, backflow and permitsRestaurants, offices, shops and apartment buildings face plumbing rules most homes never see. Here are the main ones, and what to ask a commercial plumber.Tank vs tankless water heater: how to chooseReplacing a water heater is the moment to choose the type. Here is how storage tanks, tankless units and heat pump water heaters differ, using figures from the U.S. Department of Energy.

Sources

Facts and figures in this guide come from these official and manufacturer sources, checked October 2026:

  1. City of Rio Rancho, NM – Plumbing inspections
  2. Augusta, GA – When to call for a plumbing inspection
  3. City of Las Cruces, NM – Plumbing inspections (PDF)
  4. Henrico County, VA – Residential plumbing inspection matrix (PDF)
  5. University City, MO – Plumbing permits
  6. City of St. Louis – Apply for a plumbing permit
  7. EPA WaterSense – Labeled homes

Updated October 2026 by the Plumbers Pages editorial team. General information for homeowners, not professional advice – codes and equipment differ, so follow your product’s manual and local rules. When gas, electricity, sewage or anyone’s safety is involved, call 911, your utility or a licensed plumber. How we write our guides · Plumbing glossary

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