Short answer
A shower that runs constantly while the handle spins loose has a worn-out cartridge inside the valve, and that cartridge is a part, not a new shower. Shut the water off at the shutoff for that bathroom, or at the main, because a valve in this state does not stop on its own. A plumber replaces the cartridge, trim and handle in about 2 hours when the brand is known. The valve body behind the wall only comes out when no cartridge matches an unknown brand, when the body is corroded, or when the valve has stuck and leaked for 10 years or more.
Tell a worn cartridge from a failed valve body
- Shut the water off. Use the shutoff for that bathroom if there is one, and close the main at the meter or the well tank if there is not.
- Turn the stem or handle by hand. A stem that spins with no resistance has lost its grip on the cartridge inside.
- Look at the stem where the handle grabs it. Cracks, missing chunks or stripped plastic mean the handle and stem are the fault, not the cartridge.
- Watch for the water to stop anywhere in the handle's travel. If it stops at one point, the cartridge still seals.
- Run the sink and flush the toilet in that bathroom. Low pressure or shutoff trouble at those fixtures points at the supply line, not this valve.
- Look at the wall behind the valve. A closet or bedroom wall that opens from the back changes what a valve replacement costs.
- Check the ceiling or wall below the valve for stains, soft spots or a musty smell.
If the water stops somewhere in the handle's travel, you need a handle and trim kit, which is the cheapest fix. If the stem spins freely and the water never stops, the cartridge is worn out and gets replaced. If the body is corroded, wet inside the wall, or no cartridge matches because the brand is unknown, the whole valve body comes out.
Repair or replace
| Situation | What to do |
|---|---|
| Handle or stem is broken but the water still stops when you turn the stem with pliers | Repair. A new handle, stem and trim kit restores shut-off. |
| Stem spins loose, water never stops, brand is known | Repair. Replace the cartridge, trim and handle. |
| Two valves in the same bathroom both spin loose | Repair both on one visit. One trip charge covers the pair. |
| Brand is unknown and no cartridge matches the stem | Replace the valve body with a single-handle pressure-balanced valve. |
| Valve is 10 to 20 years old and has stuck, dripped or run for years | Replace the valve body. A cartridge in a worn body fails again. |
| Water stains, soft drywall or a musty smell below the valve | Replace the valve body and have the wall opened and checked. |
| The wall behind the valve opens from a closet or bedroom | Replace through the back. No tile is cut and the job costs less. |
| Tub spout keeps dribbling after the cartridge is replaced | Replace the spout. A worn diverter sends water back down the spout. |
What it costs
Runhome contractor estimates for fixing a single-handle tub or shower valve ran from $365 to $850 to replace one valve body through the wall behind it, and up to $530 to $1,250 to fit new valve bodies on two showers, as of October 2026, including the trip and assessment.
| Option | Range |
|---|---|
| Replace the whole valve body and trim on one shower, opened from the wall behind | $365 to $850 |
| Replace the cartridge, trim, handle and spout on two tub or shower valves | $395 to $920 |
| Fit new valve bodies and trim on two tub or shower valves | $530 to $1,250 |
Can I do it myself?
Yes, on the cartridge, if you know the brand and the water shuts off. Buy the cartridge for that model, pull the handle and trim plate, pull the retaining clip, pull the old cartridge straight out with the puller in the kit, and push the new one in the same way round. Budget 2 hours for your first one, and keep the shower drain covered so the clip does not fall down it.
Hire someone for the valve body. That job means opening a wall, cutting live supply pipes, and soldering or crimping new ones in a stud bay, and a new valve has to be set at the right depth for the tile and dialed in for scald protection. Hire for it too if you cannot find a shutoff, if the brand is unknown, or if the wall below the valve is stained or soft.
What a contractor will ask you
Have these ready and you skip the back-and-forth.
- A wide photo of the whole shower wall with the handle, trim plate and showerhead in one frame, not a close-up.
- Whether the stem spins loose with no resistance, or feels stiff and still will not shut the water off.
- How long it has been running or acting up, and whether the handle is missing or broken off.
- The age of the valve, even a rough guess in years.
- The brand, even a guess such as Moen, Delta or Price Pfister.
- Whether other fixtures in that bathroom have problems, or only the tub and shower.
- Where the shutoff for that line is, or whether the main is the only shutoff you have.
- What is behind the valve wall: an interior closet or bedroom that can be opened, or masonry or a finished surround.
- Whether you want the same basic single-handle setup, or a modern pressure-balanced valve with new trim.
- Whether more than one shower in the house has the same fault.
Common questions
- Can I just turn the water off until a plumber comes?
Yes, and you should. Close the shutoff for that bathroom, or the main at the meter, so the shower is not running water you pay for. A valve left running also wears the seat inside the body and can push the repair toward a full valve replacement.
- The handle is missing, do I need a whole new valve?
No, a missing handle on its own is a trim part. A plumber matches a handle, stem and trim kit to the valve for a fraction of a valve replacement. The valve body only comes out if the cartridge inside it is also shot and no replacement part matches.
- Why does my shower keep running even with the handle off?
The cartridge inside the valve no longer seals against its seat. The handle still moves, so it feels like the shower is off, but water passes the worn seal and keeps flowing to the head. Replacing the cartridge restores the shut-off.
- Is it worth replacing the cartridge on a 20 year old shower valve?
Usually yes, as a first move, if the brand is known and the body is sound. A cartridge and trim cost far less than a valve body replacement, and most 20 year old brass bodies are still good. Go straight to the valve body if the brand is unknown, the body is green and crusted, or the shower has leaked inside the wall.
- Do I have to cut the tile to replace a shower valve?
Not if the wall behind the valve is an interior closet or bedroom. A plumber opens that side, swaps the valve, and patches drywall instead of tile. Cutting the tiled front is what makes the job expensive, so tell the contractor what is on the other side of the wall.