The Small Bathroom Remodel Plumbing Checklist (Don't Skip Step 4)

Small bathrooms punish sloppy plumbing more than any other room. With every fixture within arm's reach, even a half-inch error in a rough-in shows up in the finished tile. Use this checklist before you open the first wall.

1. Confirm Rough-In Dimensions

Standard toilet rough-in is 12" from finished wall to flange center, but 10" and 14" exist in older homes — measure before ordering. Lavatory drain is typically 18–20" off finished floor; tub drain at 14" centered on the tub opening.

2. Choose the Right Shower Valve

Pressure-balancing valves are minimum code; thermostatic valves are the upgrade worth paying for. Match the trim brand to the valve — they aren't cross-compatible.

3. Vent Every Fixture

Air admittance valves (AAVs) are allowed in many jurisdictions for islanded fixtures, but a properly tied wet vent is more reliable. Check your local code before relying on AAVs.

4. Add Shut-Off Valves at Every Fixture

This is the step DIYers skip. Quarter-turn angle stops at the toilet and each lavatory supply make every future repair a 5-minute job instead of a half-day project. Use them.

5. Pressure Test Before You Tile

Cap all openings and pressurize to 50 PSI for at least 15 minutes. Catching a weeping joint now saves a tile demo later.

Key Takeaways

• Measure rough-ins before ordering fixtures — especially in older homes.
• Thermostatic shower valves are worth the upgrade.
• Every fixture needs a vent and a shut-off — no exceptions.
• Pressure test before any finish work goes on the wall.