Sharing Plumbing Work Between a Kitchen and a Bathroom

A shutoff valve does one job: it stops water at a single branch so a crew can cut a line without flooding the slab. Notes kept at kitchen and bath riverside madame and me return to this often, because a kitchen and a bathroom in an older house in Riverside, CA, are rarely plumbed as two separate systems. Remodeling both at once means finding where they join before the first wall comes off.

How the two rooms are usually connected

Many Riverside houses built in the middle of the last century put the kitchen and the bathroom on opposite sides of one wall, or back to back through a utility chase. The drain from the kitchen sink and the drain from the vanity often meet at the same vertical stack. Cutting into one room therefore touches pipes that feed the other.

Old pipe and what shows up behind the tile

Older homes may have galvanized steel supply lines, cast iron drains and brass valves that have not turned in decades. Corroded supply pipe near a tub or shower valve gets cut back to sound metal, and a new cartridge valve is fitted in the shower while the wall is open, because the wall will not be open again.

One rough-in, two rooms

Rough-in is the stage where new supply, drain and vent lines are placed but not yet covered. A plumber who runs a new line for the kitchen sink and a new drain for the bathroom vanity in one visit saves a trip and keeps the work consistent.

The rough-in inspection covers both

The inspector from the city or Riverside County looks at open framing, pipe slope, vent connections, pressure test results and valve placement. A pressure test holds the lines under air or water for a set time, and a gauge that drops means a joint is bad. Both rooms are opened for the same visit, because once drywall closes over a pipe, the inspector cannot see it, and a failed or skipped inspection means opening finished walls.

Fixtures chosen before the pipes are placed

Plumbing fixtures decide where the rough-in lands. A wall-mounted faucet needs the supply lines at a different height than a deck-mounted one, and a vessel sink sits higher than an undermount sink in a vanity. These choices are settled before the plumber arrives, or the lines are moved after they are installed, which costs days on the calendar.

Shutting off one room at a time

Where a house has a single set of shutoffs, the plumber installs separate valves for the kitchen and for the bathroom during rough-in. That way, one room can be worked on while the other still has running water.