Direct answer: If your bathtub water will not shut off, the usual cause is a worn faucet cartridge or valve stem inside the tub handle, not the drain or overflow. First confirm whether water is coming from the tub spout, the showerhead, or both, because that tells you whether you have a shutoff problem, a diverter problem, or both.
Most likely: Most often, the tub handle is no longer closing the hot or cold side all the way because the cartridge or stem seals are worn, mineral-stuck, or broken.
Start with the easy clues: which outlet is still flowing, whether one handle feels loose or stripped, and whether the water slows when you push or wiggle the handle. Reality check: a tub that keeps running can waste a surprising amount of hot water fast. Common wrong move: buying a new spout because water is visible there, even though the shutoff parts are back in the wall valve.
Don’t start with: Do not start by replacing the tub spout or taking apart the drain. Those parts do not control shutoff.
Even with the handle turned off, a steady stream or strong drip keeps coming out of the bathtub spout.
Start here: Start with the handle and valve branch. A worn bathtub faucet cartridge or bathtub faucet stem is most likely.
The tub was used for a shower, and water keeps dribbling or running from the showerhead after the handle is off.
Start here: Separate a true shutoff failure from a diverter issue. If the tub spout is also flowing, the valve is not closing. If only the showerhead keeps dripping briefly, that can be normal drain-down.
The handle spins too far, feels sloppy, or takes extra force to shut the water down.
Start here: Check the handle attachment first, then the cartridge or stem behind that handle. A loose handle can hide a valve that is not actually turning fully.
On a two-handle tub faucet, one side keeps feeding water even when the other side is off.
Start here: Focus on the specific hot or cold bathtub faucet stem or cartridge for that side, not the whole tub assembly.
Single-handle tub faucets that keep running usually have a cartridge that no longer seals when turned to off.
Quick check: Shut the handle firmly to off. If flow stays nearly the same and the handle feels normal, the bathtub faucet cartridge is the first suspect.
Two-handle tub faucets often fail at the stem washer or stem assembly, especially if one side keeps feeding water.
Quick check: Turn off one handle at a time. If the flow changes when you close only the hot or only the cold side, that side's bathtub faucet stem is likely worn.
Sometimes the handle turns but does not fully move the valve underneath, so the water never reaches true off.
Quick check: Remove the decorative cap if present and check whether the handle screw is loose or the handle hub is rounded out.
If water is still running and some of it is being sent upward, the diverter may be hanging up, but the main shutoff problem is still in the valve.
Quick check: With the water still flowing, lower or release the diverter. If water shifts back to the spout but does not stop, the valve is the main failure and the diverter may be secondary.
Tub shutoff problems get misread all the time. You want to separate a valve problem from normal showerhead drain-down or a stuck diverter.
Next move: If the showerhead drip fades away and the tub spout is dry, you likely do not have a shutoff failure. If the tub spout keeps flowing or both outlets keep running, keep going. The valve is not closing fully.
What to conclude: A steady flow from the spout points to the bathtub faucet cartridge or stem. Water redirected to the showerhead can mean the diverter is also sticking, but it is rarely the only reason the water will not shut off.
A loose or stripped handle is a simple fix and can mimic a bad valve because the stem underneath is not being turned all the way.
Next move: If the water shuts off normally once the handle is tightened or repositioned, replace or secure the bathtub faucet handle and recheck for full off. If the stem turns to its stop and water still runs, the internal shutoff parts are worn.
What to conclude: A loose handle is the easy win. If the handle is doing its job and the water still will not stop, the failure is inside the valve body at the cartridge or stem.
This is the point where the right replacement path becomes clear. Single-handle tub valves usually use a cartridge. Two-handle tub faucets usually use separate stems.
Next move: If you identify the valve style and the failed side, you can buy the right repair part instead of guessing. If the valve style is unclear, the trim is buried, or the part will not come free without heavy force, stop and bring in a plumber.
Once the bad part is identified, replacing that exact shutoff component is the repair that usually solves the problem.
Next move: If the water shuts off cleanly and the handle travel feels normal, finish reassembly and caulk only where the trim originally required it. If the new part is installed correctly and the tub still will not shut off, the valve seat or valve body may be damaged, or you may have the wrong replacement part.
At this point you do not want to keep forcing parts into an uncertain valve body and turn a simple repair into an open-wall job.
A good result: If the water now shuts off and there is no hidden leakage, the repair is done.
If not: If you still have uncontrolled flow or hidden leakage, leave the water off to that tub and escalate.
What to conclude: Persistent flow after the normal wear parts are replaced points to a deeper valve problem, not another random part swap.
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Most of the time the shutoff part inside the valve is worn out. On a single-handle tub faucet that is usually the bathtub faucet cartridge. On a two-handle tub faucet it is usually the hot or cold bathtub faucet stem.
Usually no. The spout is just the outlet. If water keeps coming out of it, the valve in the wall is still letting water through. A stuck diverter can redirect water, but it does not normally create the main shutoff failure.
A short drip after shower use can be normal because water trapped in the riser pipe drains out. A steady flow that keeps going is different and points to a valve that is not closing or a diverter that is hanging up.
Not automatically. If one side is clearly the problem, start there. If both handles are equally old and you already have the water off and trim apart, some homeowners choose to do both, but diagnosis should still lead the decision.
Then the replacement may be the wrong fit, installed incorrectly, or the valve seat or valve body may be damaged. At that point stop forcing it. Shut the water off and inspect carefully or call a plumber if the valve body itself is the problem.
Usually not for a normal cartridge or stem replacement. Most shutoff repairs are done from the front at the handle and trim. You only move toward wall access if there is hidden leaking, a damaged valve body, or seized parts that cannot be removed safely from the front.