Pipe installation: what to know

What the job involves, what changes the price, and what to ask a pro.

What pipe installation is

Pipe installation adds new supply or drain lines for a remodel, an addition or a new fixture. It is the work behind a new bathroom, kitchen or laundry room, and it is best planned before any walls are closed.

Signs you need it

  • You are adding a fixture that has no existing line, such as a second bathroom, a laundry hookup or an outdoor sink
  • A remodel moves a sink, shower or toilet farther from the current drain than the drain can reach at the right slope
  • An addition or basement finish needs new supply and drain connections
  • The existing supply is too small for the new fixtures, and the pressure drops when two fixtures run
  • The new layout needs a vent, and there is no existing vent close enough to tie into

What the pro does

  • Check the existing supply size, the pressure and the drain slope, and map the route before any wall is cut
  • Plan the vent so the drains can flow and the traps keep their seal, including where it exits the roof or ties into an existing stack
  • Install supply lines in PEX or copper with the fittings and support spacing that the material needs
  • Set drain lines in PVC or ABS with a steady slope, and mark the slope on the framing as the run goes in
  • Pressure test the supply and water or air test the drain before the walls are closed
  • Give the customer a written map of the new routes and shutoffs for future work

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Distance from the existing supply and drain, since longer runs need more pipe and fittings
  • Material choice: PEX, copper, PVC and ABS each change the materials and the labor
  • Whether walls, floors or ceilings must be opened to route the line
  • Vent design, including roof penetrations or a tie-in to an existing stack
  • Whether a slab must be cut or a trench dug for an under-slab run
  • Number of fixtures and whether a single line has to serve more than one

What a written quote should spell out

  • Route of the supply and drain lines, with the material and size of each
  • Vent route and how it ties into the existing system
  • Slope of each drain run and any cleanouts added
  • Pressure test and drain test method
  • Restoration of walls, floors or ceilings, and who handles it

Questions to ask before you hire

  • Does the existing supply and drain have the capacity for the new fixtures?
  • Where will the vent go, and does it tie into an existing stack or need a new roof penetration?
  • What material will you use for supply and drain, and why?
  • How will you hold the drain slope, and how will you check it before the walls close?
  • Will you pressure test and water test the lines before the walls are closed?
  • Who pulls the permit and schedules the inspection?

Red flags

  • Pro who runs drain lines without a vent plan
  • Pro who installs a drain run flat or uphill in any section, which holds waste
  • Pro who says the walls will close before the inspection or the test
  • Pro who uses one material for supply and drain without explaining the fittings for each

What you can do yourself

A homeowner can plan the layout, sketch the routes, and help open or patch walls where a pro has approved it. Do not cut into an existing supply or drain or add a vent yourself, since a wrong slope or a missing vent causes slow drains, sewer gas and leaks.

Licenses and permits

New supply and drain lines are commonly licensed plumbing work, and many areas require a permit and inspection for new piping. Check with your state or local licensing agency and the local building department before work starts.

Pipe installation questions

How far can a drain run go from the stack?

The limit depends on the fixture, the pipe size and the slope, and the local code sets the maximum. Ask the pro to show the route on the plan before the walls open.

Can I use PEX for drains?

No. PEX is used for supply lines. Drains use PVC or ABS, or cast iron in older work, with the slope and vent built to carry waste.

Why does a new drain need a vent?

A vent lets air into the drain so water flows and the trap keeps its seal. Without one, drains gurgle and the trap can lose its seal, letting sewer gas into the room.

Do I need to be home during the install?

You need access to the work area and the main shutoff. Expect water to be off for parts of the day while tie-ins are made.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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