Bathroom Renovation Plumbing Checklist — Don't Skip These Steps

Document the center of every drain, the height and location of every supply stub-out, and where vent stacks run. Measure from two fixed reference points (exterior walls) so you can recreate positions on the new plan. This baseline tells you what you can reuse vs. what must move — and moving drains through a concrete slab costs 5–10× more than through wood framing.

Every fixture needs a drain connection within specific distances from a vent stack (per local code, typically 5–8 feet for a toilet, 3.5–5 feet for a sink). Moving a vanity 2 feet left might put it beyond legal vent distance, requiring a new vent penetration through the roof. Plot every fixture against your existing vent stack locations before finalizing the layout.

Some jurisdictions require copper supply lines (no PEX) in certain applications. Drain requirements vary between ABS, PVC, and cast iron depending on your area and whether the home is single-family or multi-unit. Pull your local plumbing code requirements before buying materials. Using non-approved materials means failing inspection and re-doing the work.

Rain showerheads and body sprays need 45–80 PSI to perform properly. If your home runs 30–40 PSI (common in older homes or those far from municipal supply), adding high-flow fixtures will produce a disappointing trickle. Test static pressure at your main with a $10 gauge before committing to fixture selections that require strong pressure.

The toilet flange must sit flush with (or no more than ¼ inch above) the finished floor surface. If you're adding tile, calculate the tile + mortar thickness and set the flange at that height above the subfloor. A flange set too low causes rocking and wax seal failure; too high means the toilet won't sit flat. This is the #1 cause of toilet leaks after a renovation.

Standard heights: toilet supply 6 inches above finished floor, 6 inches left of center; sink supply 20–22 inches above finished floor; shower valve 48 inches above finished floor (adjustable by preference). Tub filler 4 inches above tub rim. Get fixture spec sheets BEFORE rough-in — wall-mount faucets have exact supply positions that vary by manufacturer.

Every horizontal drain pipe must slope toward the stack at a minimum of ¼ inch per foot. Too little slope and waste sits in the pipe, clogging repeatedly. Too much slope (over ½ inch per foot) and water outruns solids, leaving them stranded. Use a 4-foot level to check slope on every horizontal section before walls close.

Every trap needs a vent within code-allowed distance to prevent siphoning. A toilet without adequate venting gurgles, drains slowly, and can pull water out of nearby sink traps (allowing sewer gas into the room). Verify each vent ties into the main stack above the flood rim of the highest fixture it serves. Improper venting is the most common reason for failed plumbing inspections.

After completing supply rough-in, cap all outlets and pressurize the system to 80 PSI (or per local code) for a minimum of 2 hours. Watch the gauge — any pressure drop indicates a leak. It's far cheaper to find and fix a leaking joint now than after drywall, tile, and paint. Most inspectors require a witnessed pressure test for permit sign-off.

Braided stainless steel supply lines handle pressure spikes and last 10+ years. Plastic supply lines degrade, become brittle, and are the #1 cause of catastrophic bathroom floods in homes 5–10 years old. Spend the extra $5 per connection for stainless braided lines and replace any existing plastic connectors while fixtures are disconnected.

Every toilet, sink, and appliance should have its own quarter-turn shut-off valve on both hot and cold supply lines. If a toilet supply line bursts at 2 AM, you need to stop water in 10 seconds — not run to the basement to shut off the whole house. Use quarter-turn ball valves, not multi-turn gate valves that seize up from disuse.

A rocking toilet breaks its wax seal within weeks, causing a slow leak into the subfloor that you won't notice until the floor is spongy. After setting the toilet, try to rock it in all directions. If it moves at all, shim with plastic toilet shims (never hardwood — it rots), then caulk around the base leaving the back uncaulked so any future leak is visible rather than hidden.

Fill every sink and tub to the overflow, then release. Watch under the fixture for drips at the P-trap, drain tailpiece, and overflow connection. Flush the toilet twice and check the base and supply connection. Run the shower for 5 minutes and check the ceiling below for any moisture. Do this before the final walkthrough — leak damage starts immediately.

Code requires hot water on the left side of every fixture (facing it). Crossed connections create scald risk and confuse everyone who uses the bathroom. If supply lines were crossed during rough-in, fix them now — it's much harder after escutcheons and handles are installed. Test by running hot only and confirming which handle activates it.

Before access panels close and vanity skirts go on, photograph every connection point. If a leak develops in year 3, these photos tell you exactly what's behind the wall and where to cut access — saving hours of exploratory demolition. Store photos with your home maintenance records.

If you added a soaking tub (60–80 gallons), large rain shower, or body sprays, your existing 40-gallon water heater may not keep up. Run all new fixtures simultaneously and check if hot water holds temperature for the duration of a typical use. If it runs cold in 10 minutes, you may need a larger tank or tankless unit.

An open (unsigned) plumbing permit creates problems at home sale — title companies flag it, and you'll need to expose finished work for re-inspection. Schedule final inspection while work is fresh and your plumber is still available to address any corrections. Keep the signed permit card with your home documents permanently.