Leaks only when the tub is draining
The area stays dry while the tub is full, then starts dripping once you pull the stopper or open the drain.
Start here: Start with the bathtub drain body, drain shoe seal, and overflow connection.
Bathtub leak troubleshooting
Bathtub Leaking
Direct answer: A bathtub leak usually comes from one of four spots: the tub drain, the overflow opening, the tub spout, or the plumbing connections behind the wall. The fastest way to sort it out is to see whether it leaks only while the tub is filling, only while it is draining, or even when nobody is using it.
Most likely: Most often, the first real culprit is a loose or failed bathtub drain seal, a leaking overflow gasket, or a tub spout that lets water run back into the wall.
Start with the first wet point, not the stain on the ceiling below. A slow drip can travel along framing and show up several feet away from the actual leak. Reality check: a leak that only shows up during baths is usually on the drain or overflow side, while a leak that appears with the shower running points hard at the spout, valve trim, or wall entry.
Don’t start with: Do not start by caulking around the tub or buying random trim parts. Caulk hides the path of the leak and usually does nothing for a bad drain seal or a leak behind the wall.
Leaks during drainingCheck the bathtub drain and overflow first.
Leaks with water supply onCheck the tub spout, valve area, and wall plumbing before touching the drain.
Last reviewed: 2026-04-04
What kind of bathtub leak are you seeing?
Leaks while filling or while the shower runs
Water shows up before the tub drains, or the leak is worse when the spout or shower is running.
Start here: Start with the tub spout, valve trim area, and supply-side plumbing behind the wall.
Leaks only when water reaches the overflow
A normal shallow fill stays dry, but a deeper bath or splashing near the overflow makes water appear.
Start here: Start with the bathtub overflow plate and overflow gasket.
Water appears around the outside of the tub
The floor or ceiling gets wet, but the leak source is not obvious from above.
Start here: Dry everything, use short test runs, and trace the first wet point before assuming the tub itself is cracked.
Most likely causes
1. Bathtub drain seal or drain body leak
This is a common cause when the leak shows up only after the stopper is opened or when a full tub starts emptying.
Quick check: Dry the underside access area if you can reach it, then drain a half tub and watch the drain shoe and drain body connection for the first drip.
2. Bathtub overflow gasket leaking
If the leak happens only when water rises to the overflow opening or when kids splash hard against that wall, the overflow is the prime suspect.
Quick check: Run water directly into the overflow opening for 20 to 30 seconds while watching below or behind the access side.
3. Tub spout leaking into the wall
A loose spout or failed spout connection can send water back into the wall when the tub is filling or when the shower diverter is used.
Quick check: With the wall and floor dry, run the tub spout and then the shower. Look for water at the wall around the spout or from the access panel side.
4. Leak at the valve trim or supply connections behind the wall
If water appears even before the drain is used, especially with the shower running, the leak may be at the mixing valve area or nearby piping.
Quick check: Remove the escutcheon only if it comes off easily, then look for fresh water trails while the shower runs briefly.
Step-by-step fix
Step 1: Pin down when the leak happens
You will save time by separating drain-side leaks from supply-side leaks before taking anything apart.
- Wipe the tub, floor, access panel area, and any visible piping dry.
- Put a dry paper towel under the drain area or below the access opening if you have one.
- Run three short tests in order: fill from the spout for a minute, run the shower for a minute, then drain a few inches of water.
- Note exactly which test creates the first fresh drip.
Next move: You now know whether to stay on the drain/overflow side or move to the spout/wall side. If the leak pattern is still unclear, stop using the tub until you can open an access panel or inspect from below with better visibility.
What to conclude: A leak during draining points to the bathtub drain or overflow assembly. A leak during filling or shower use points to the tub spout, valve trim area, or plumbing in the wall.
Stop if:
- Water is actively dripping into a finished ceiling or wall cavity.
- You see swelling drywall, loose tile, or soft flooring getting worse during testing.
- You cannot test without causing more water damage.
Step 2: Check the bathtub overflow before the drain
The overflow is easy to miss, and it can leak only at higher water levels, which makes it look like a drain problem.
- Fill the tub to just below the overflow opening and confirm the area stays dry.
- Then add water until it enters the overflow, or pour water directly into the overflow opening with a cup.
- Watch the backside access area, ceiling below, or floor edge for the first drip.
- If the overflow plate is loose, snug the screws evenly without cranking them down hard.
Next move: If tightening the plate stops the leak, the gasket was likely not compressed evenly and you may be done. If water still leaks when the overflow is used, the bathtub overflow gasket is likely misaligned, hardened, or split.
What to conclude: A leak tied specifically to the overflow opening usually means the overflow gasket or overflow plate connection needs attention, not the main drain.
Step 3: Test the bathtub drain seal and drain body
If the tub holds water fine but leaks once draining starts, the drain connection is the strongest suspect.
- Fill the tub with a few inches of water and let it sit for 10 to 15 minutes without draining.
- If it stays dry while holding, pull the stopper and watch for drips as water moves through the drain.
- From the access side or from below, look at the bathtub drain body, drain shoe, and the connection where the drain meets the tub.
- Check for looseness at the drain flange from above, but do not force it if it is seized.
Next move: If a careful snugging of a loose drain flange stops the leak, monitor it through a full drain cycle and recheck later. If the leak starts only when water is moving through the drain, plan on replacing the bathtub drain assembly or resealing that connection.
Step 4: Check the tub spout and wall-entry area
A spout leak can send water behind the wall and mimic a drain leak, especially when the shower diverter is used.
- Dry the wall around the tub spout and the underside access area if present.
- Run water from the tub spout for a minute and look for seepage where the spout meets the wall.
- Then engage the shower diverter and watch for water appearing at the spout base, wall opening, or access side.
- If the spout is obviously loose or wobbly, that supports a bad tub spout connection.
Next move: If tightening or replacing the tub spout stops the leak, retest with both tub and shower flow before closing anything up. If the leak is still coming from inside the wall, the problem is likely at the valve body, shower riser, or supply connections rather than the spout itself.
Step 5: Make the repair call before damage spreads
Once you know the leak pattern, the right next move is usually straightforward and cheaper than letting hidden water keep working.
- Replace the bathtub overflow gasket if the leak happens only when water enters the overflow.
- Replace or reseal the bathtub drain assembly if the leak starts when the tub drains.
- Replace the tub spout if water leaks at the spout wall opening or the spout connection is loose and worn.
- Call a plumber if the leak is behind the wall at the valve or supply piping, or if there is no safe access to confirm the source.
A good result: After the repair, run the same fill, shower, and drain tests again and check the area below after 15 to 30 minutes.
If not: If the leak remains after the obvious part is replaced, stop using the tub and open access or bring in a plumber before more finish materials get wet.
What to conclude: The right repair depends on the first wet point. Drain and overflow leaks are often manageable DIY jobs. Hidden wall leaks are where the risk climbs fast.
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FAQ
Why does my bathtub leak only when I drain it?
That usually points to the bathtub drain assembly, drain shoe seal, or a nearby drain connection. If the tub can sit full without leaking but starts dripping once water moves out, the drain side is the first place to look.
Why does my bathtub leak only when it is full?
If the leak starts only when the water level reaches the overflow opening, the bathtub overflow gasket is the likely problem. If it leaks before the water gets that high, look harder at the spout, valve wall, or a crack around the drain area.
Can a tub spout cause a leak behind the wall?
Yes. A loose or failed tub spout connection can send water back into the wall when the tub is running or when the shower diverter is engaged. That leak often shows up below the tub and gets mistaken for a drain problem.
Should I caulk around the bathtub drain to stop a leak?
No. The drain has to seal at the actual drain body and gasket, not with surface caulk around the visible opening. Caulk may hide the symptom for a short time, but it does not fix a failed bathtub drain seal.
Is a leaking bathtub an emergency?
It can be if water is entering a ceiling, wall, or floor cavity. A slow bathtub leak can do expensive damage because it often stays hidden. If you cannot clearly contain it or the source is inside the wall, stop using the tub and get it repaired promptly.
How do I know if the tub itself is cracked?
Look closely around the drain, overflow, and floor of the tub for hairline cracks, flexing, or staining that returns even after the drain and overflow test dry. If the tub surface is cracked around the drain opening, stop tightening parts and address the tub damage first.