The setup
In this invented example, a two-story house in Fullerton has a primary bathroom upstairs directly over the family room. A brown ring appears on the family room ceiling and grows slowly over two weeks. The owners fear a burst pipe in the ceiling.
They start by asking a simple question: does the stain get wetter when nothing is being used, or only after someone showers?
Their fixture-by-fixture test
- Meter check.With everything off, the meter is still. A pressurized supply leak looks unlikely.
- Sink.Filling and draining the sink leaves the ceiling unchanged.
- Toilet.Several flushes leave the ceiling unchanged.
- Shower drain only.Pouring buckets of water straight down the drain, without wetting the walls, leaves the ceiling unchanged.
- Shower walls and door.Spraying the walls and the door threshold for several minutes darkens the stain.
What the results mean
- IfMeter still with nothing runningSupply lines in the ceiling are probably not leaking.
- IfDrain test dryThe drain pipe and its connection are probably sound.
- IfWet only when walls and threshold are sprayedWater is getting past grout, caulk, the door seal or the shower pan.
The invented outcome
A licensed plumber confirms the drain holds water and the valve behind the wall is dry. The likely culprit is cracked caulk where the glass door meets the curb, letting water run under the threshold and onto the subfloor. The plumber suggests resealing and, if staining continues, testing the shower pan itself.
The ceiling is left open for drying before it is patched, and the owners stop using that shower until the seal has cured.
Terms from this example
- Shower pan
- The waterproof layer under a tiled shower floor that directs water to the drain.
- Curb
- The raised edge at the shower entrance.
- Flood test
- Plugging the drain and holding water in the shower floor to check the pan.
What helped in this example
- Testing one fixture at a time, with someone watching below.
- Separating the drain test from the wall spray test.
- Using the meter to rule out a supply leak early.
- Letting the ceiling dry before patching.
Common questions
Is this a real job?
No. It is a hypothetical example used to illustrate the steps.
Can a shower leak show up far from the shower?
Yes. Water can run along joists before soaking through, so the stain may be offset from the source.
Who fixes a shower pan leak?
It may involve a plumber, a tile contractor or both, depending on the cause. Ask whoever inspects it to explain.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.