In an older building, the plumbing behind a kitchen or bathroom wall may be original galvanized supply pipe and a cast-iron drain stack. Once the wall is open, replacing that pipe is far easier than it will ever be again. Leaving it in place means new fixtures and finishes sit on top of the oldest part of the system.

The key planning question is not only what is inside the room, but what the new work connects to beyond it. A new shower drain tied into a heavily scaled cast-iron line, or new supply lines fed by narrowed galvanized pipe, can undercut the remodel.

Planning the plumbing

  1. Survey before demolition

    Have a plumber identify supply and drain materials serving the room, and camera the drain if it is old cast iron or clay.

  2. Decide the replacement boundary

    Choose how far beyond the room to replace pipe, ideally to a sound tie-in point.

  3. Plan new fixture needs

    Larger showers, added sinks or a new dishwasher may need different drain sizes, vents or supply lines.

  4. Coordinate permits

    Remodels with plumbing changes often need permits; check with the City of Fullerton early.

  5. Inspect before closing walls

    New piping is tested and, where required, inspected before walls and floors are closed up.

Replace while the walls are open

  • Galvanized supply lines in the room and up to a sound connection
  • Cast-iron drain sections and fittings in the room
  • Old fixture shutoff valves
  • Vent connections that were altered or undersized in past work
  • Gas lines to a range if the kitchen layout changes
  • Any abandoned pipe that could be capped or removed

Room-only plumbing versus planning beyond the room

Room only

  • Smaller plumbing scope in the remodel budget
  • New pipe ties into whatever is behind the next wall
  • Old pipe outside the room keeps aging
  • Future repairs may mean opening new finishes

Planned beyond the room

  • Tie-in points are chosen where pipe is sound
  • Fewer weak joints between old and new
  • May extend into adjacent walls, crawlspace or attic
  • Fits well with a phased whole-house repipe plan

Questions for the plumber and contractor

  1. What pipe materials serve this room now?
  2. Where will the new pipe connect to existing pipe, and what condition is it in?
  3. Do the new fixtures need different drain or vent sizes?
  4. Who arranges plumbing permits and inspections?
  5. Is the plumbing contractor licensed separately, and can I check at cslb.ca.gov?

Common questions

Should I repipe the whole house during one remodel?

It depends on budget and how much galvanized pipe remains. Some owners replace the remodel area and plan the rest; others use the remodel as the start of a full repipe.

Can I keep the old cast-iron tub drain?

Sometimes, if it is in good condition. Ask the plumber to inspect it while the floor is open, because replacing it later can mean removing new finishes.

Do I need a separate plumber if I hire a general contractor?

Many general contractors use plumbing subcontractors. Ask who will do the plumbing and check that person's or company's license.

General information for Downtown Fullerton, not a quote or professional advice. In an emergency, call 911.