A ceiling leak below a bathtub can involve the waste and overflow, supply plumbing, shower enclosure or a neighboring fixture. Timing helps guide an investigation but does not identify one failed part. Stop using a known leaking tub, preserve observations already made, avoid wet electrical equipment and arrange a safe professional assessment.
Match the timing to the cause
Write down when the stain grows. Pay attention to three moments: while the tub fills, while someone showers, and when nothing is running at all.
For a bath with water jets, record any leakage already noticed during jet operation too. A whirlpool's circulation-leak checklist explains that additional water path and why the timing does not prove one failed fitting. Stop using a known leaking bath instead of repeating the leak.
It drips while the tub is filled or full. The drain, overflow or their connections are possible water paths, but the timing does not identify which seal or fitting failed. Oatey describes the assembly this way: "A bath waste and overflow system is a critical plumbing component that connects your bathtub to your household drain line." Record whether leakage was noticed during filling, while water stood in the tub or near the overflow level; have the complete installation assessed rather than assuming one gasket from that history.
It drips only while someone showers. Tell the provider about the shower spray, tub-wall joints, surround, spout and enclosure edges. Water at those locations can be relevant, but shower timing does not prove a caulk failure or rule out supply and drainage connections. Do not run the shower again over a known ceiling leak to test those possibilities.
It drips even when nothing is running. A pressurized supply line, shower valve or fitting behind the wall is among the possibilities to investigate. Continuing dampness alone does not prove that diagnosis. Read leaking shower valve behind the wall for relevant signs, and use the water-meter leak-test guide only where its ordinary observations can be made safely. Pass the existing history to the provider.
It drips after the tub drains or after someone flushes. A drain or trap joint under the tub, or the toilet next to it, is the suspect. Oatey's wax ring guide says: "If you're replacing the wax ring due to a leak at the toilet base or water stains on the ceiling below, identify the root cause before buying materials." A toilet with a failing wax ring can stain the ceiling below just as a tub can, so check both. See toilet leaking at the base if the floor around the toilet is wet.
Preserve observations before any diagnostic test
Do not refill a tub, send water into its overflow, run its jets or aim shower spray at its walls to reproduce a known ceiling leak. Stop use and have the provider establish safe access, electrical precautions and the appropriate assessment. The provider can decide which controlled test is appropriate to the actual assembly and condition.
Keep observations already made: when water appeared, which fixture had been used, whether jets were running, the visible stain and any recent plumbing work. Take photographs only from a safe location. A bucket does not make more water, a wet electrical area or a damaged ceiling safe.
Oatey's waste-and-overflow FAQ says, "If you are just replacing an existing bath waste/overflow with a new one, a draining test will work." Its procedure requires inspecting all connection points behind the tub. For a larger installation, it directs checking with local building officials about the required test. Those instructions concern inspection of a newly replaced assembly; they are not a reason to refill a bathtub already leaking through a finished ceiling.
Have the provider choose any controlled test after assessing the actual leak and access. Do not open a ceiling, remove a powered bath's access cover or reach toward wet wiring to make the connections visible. Electrical Safety Foundation guidance calls for qualified evaluation of water-damaged electrical equipment and warns against returning power without proper evaluation.
What you can fix and what to open up
Do not assume that replacing caulk, grout or a spout seal has repaired a ceiling leak before its cause is identified. Arrange the assessment first. Any confirmed surface repair still needs a dry, sound area and the actual material and fixture instructions; painting or caulking over wet or moldy material does not solve the water problem.
The drain and overflow are a different matter. The gaskets sit under the tub, so reaching them means an access panel behind the tub, which many second-floor bathrooms have on the wall of the adjoining closet or hallway, or opening the ceiling below. A leaking shoe or gasket is a straightforward repair when there is access. If there isn't, the repair may mean cutting an access opening. Don't over-tighten plastic connections, because cracking one turns a slow drip into a steady one.
If the leak is behind the wall, from a supply line, valve or drain pipe you can't reach, stop and have it located before anyone cuts tile. A pro uses moisture meters and thermal imaging so the opening is small. HQ Plumbing & Air offers leak detection for exactly this. We're licensed and insured, we give you a free estimate, and you get the price up front before work starts. If water is flowing and you can't stop it, we're available 24/7.
Deal with the ceiling too
A stopped leak doesn't finish the job. EPA advises: "It is important to dry water-damaged areas and items within 24-48 hours to prevent mold growth." The stain is only what shows. The insulation and drywall above it can stay wet for days. EPA also warns that "Absorbent or porous materials, such as ceiling tiles and carpet, may have to be thrown away if they become moldy." Soft, sagging or crumbling drywall should be cut out and replaced rather than painted over.
Two safety points. If the water is dripping near a light, fan or smoke detector, treat it as an electrical hazard, and read water dripping from a smoke detector or ceiling light before you touch anything. And if you rent or live in a condo or townhome, the pipe may not be yours to fix; see who fixes a leaking pipe in a condo or townhome.
Keep the tub out of use, record the timing already observed and have the cause assessed before a controlled test or repair. Address the ceiling and other water-damaged materials after the water source is stopped. A matching timing pattern or a dry-looking surface does not prove that the complete repair is sound.
Before replacing the flange, read removing a bathtub drain for model-specific tool choices, access to the waste-and-overflow assembly and leak testing.