What a tub faucet stem is and why it fails
The stem is the part inside your faucet handle that turns to open and close the water. It's a shaft with a washer or cartridge at the end that actually stops the flow. When your handle becomes hard to turn, leaks around the base, or won't shut off completely, the stem has usually worn out or corroded inside.
Stems fail because water sits inside them year-round. Minerals in your water build up, metal parts rust, and rubber washers crack. A leaking stem wastes water and can stain your tub. The good news: replacing one takes about an hour and costs $15 to $40 in parts, depending on your faucet type.
Before you start, turn off the water supply to your tub. Look under the sink or in the basement for the shutoff valve marked for the bathroom. Turn it clockwise until it stops. If you can't find it, turn off the main water supply to the house.
Key Takeaways
- The stem is the shaft inside your handle that controls water flow, and it wears out from mineral buildup and corrosion over time.
- You must identify your faucet type—compression, cartridge, or ball—because each uses a different stem and removal method.
- Compression faucets have two separate stems (one for hot, one for cold) that you replace individually with a new washer and seat.
- Cartridge and ball faucets use a single sealed cartridge or ball assembly that you remove as one piece and replace whole.
- If you cannot remove the stem by hand or with basic tools, or if the valve seat is damaged, call a plumber rather than force it.
Identify your faucet type before you buy parts
The stem you need depends on whether your faucet is a compression, cartridge, or ball type. Each one comes apart differently and uses different replacement parts. Buying the wrong stem wastes money and time.
Compression faucets have two separate handles—one for hot water, one for cold. When you turn the handle, you feel resistance, like you're screwing something down. These are the oldest type and most common in older homes. Each handle controls its own stem.
Cartridge faucets have one or two handles that move side to side or up and down without turning. The handle controls a single cartridge inside the faucet body. Moen, Delta, and Kohler all make cartridge faucets.
Ball faucets have one handle that moves in all directions over a rounded bump. Moen makes most ball faucets. The handle controls a ball-shaped part inside that mixes hot and cold water.
If you're unsure, take a photo of your faucet and show it to the staff at a hardware store, or search your faucet brand and model online. Knowing the type before you go to the store saves a trip back.
How to replace a compression faucet stem
Compression faucets are the easiest to repair yourself because the stem is straightforward and inexpensive. You will need an adjustable wrench, a screwdriver, a stem removal tool (also called a packing nut wrench), and a replacement stem kit that matches your faucet brand.
Start by removing the handle. Look for a small screw under the handle or behind a decorative cap. Remove the screw and lift the handle off. Then use your wrench to unscrew the packing nut—the large nut directly under where the handle was. Turn it counterclockwise until it comes free.
Once the packing nut is off, you can pull the stem straight out by hand or with the stem removal tool if it's stuck. The stem will have a washer and a small screw at the bottom. Unscrew the washer and replace it with a new one from your kit. If the valve seat (the part the washer presses against) is pitted or corroded, you may need to replace that too—your kit should include a seat wrench and a new seat.
Slide the new stem back in, screw the packing nut back on hand-tight, then use your wrench to snug it. Don't over-tighten or the handle will be hard to turn. Screw the handle back on and test the water. If it still leaks, the valve seat may need replacement—this is when to call a plumber.
How to replace a cartridge faucet stem
Cartridge faucets are sealed units, so you replace the entire cartridge rather than just a washer. You will need an adjustable wrench, a screwdriver, and a cartridge puller tool (specific to your faucet brand—this is important). The cartridge itself costs $20 to $60 depending on the brand.
Remove the handle by finding the set screw (usually hidden under a cap or in a small hole on the handle) and unscrewing it. Lift the handle away. You may see a decorative collar or trim ring—unscrew that too if it's in the way.
Look for the cartridge body inside the faucet. It will be a cylinder with a flat top. Use your cartridge puller tool to grip it and pull straight up. The tool is brand-specific—a Delta cartridge puller won't work on a Moen cartridge. If you pull without the right tool, you can break the cartridge inside the faucet body, and then you need a plumber.
Once the old cartridge is out, slide the new one in, making sure the flat side faces the same direction as the old one did. Screw the collar back on, replace the handle, and test. If water still leaks from the handle, the cartridge may not be seated all the way—pull it out and push it in again, making sure you hear or feel a click.
How to replace a ball faucet stem
Ball faucets have a rounded metal or plastic ball inside that mixes hot and cold water. When the ball wears out, the whole ball assembly must be replaced. You will need an adjustable wrench, a screwdriver, and a ball assembly kit for your faucet brand (usually $30 to $50).
Remove the handle by loosening the set screw on the side or underneath. Lift the handle away. Then look for the cap or collar that holds the ball in place—it's usually a large hexagonal nut. Use your wrench to turn it counterclockwise and remove it.
The ball will now lift out. Underneath it, you'll see springs and seals. These wear out too, so your kit should include replacements. Remove the old springs and seals with needle-nose pliers and set the new ones in place. Then drop the new ball in, making sure any flat side or key aligns with the slot in the faucet body.
Screw the collar back on hand-tight, then use your wrench to snug it—not hard, just firm. Replace the handle and test the water. If it leaks from the spout, the ball may not be seated correctly. Remove the collar and ball, check that the seals are in place, and try again.
When to stop and call a plumber
Some situations call for professional help. If the stem won't come out no matter how hard you pull, forcing it can break the faucet body and create a much bigger repair. If the valve seat is pitted or corroded and you don't have a seat wrench and replacement in your kit, a plumber can replace it. If water leaks from inside the wall after you finish, you may have damaged a connection—a plumber can find and fix it.
Also, if your faucet is mounted on the tub wall rather than the sink counter, the job is more complex because you may need to remove trim rings or access panels. A plumber can do this faster and with less risk of damaging the wall.
The cost of a service call is usually $100 to $200, but it's worth it if you're unsure or if the faucet is old and fragile. A plumber can also tell you if the whole faucet should be replaced rather than repaired.
Tools and parts you'll need
| Tool or Part | Compression Faucet | Cartridge Faucet | Ball Faucet |
|---|---|---|---|
| Adjustable wrench | Yes | Yes | Yes |
| Screwdriver (flat and Phillips) | Yes | Yes | Yes |
| Stem removal tool | Yes | No | No |
| Cartridge puller | No | Yes (brand-specific) | No |
| Replacement stem or cartridge kit | $15–$25 | $20–$60 | $30–$50 |
| Needle-nose pliers | No | No | Yes |
Frequently Asked Questions
Do I need to turn off the water before I start?
Yes. Always shut off the water supply to your tub before you remove any part of the faucet. If you don't and the stem comes out, water will pour into the tub and possibly down into the wall. Find the shutoff valve under the sink or in the basement and turn it clockwise until it stops.
What if the stem is stuck and won't come out?
Mineral buildup can freeze a stem in place. Spray penetrating oil (like WD-40) around the packing nut and let it soak for 15 minutes. Then try again gently. If it still won't budge, stop—forcing it can crack the faucet body. Call a plumber at this point.
How do I know which brand my faucet is?
Look on the faucet spout or handle for a brand name stamped or printed on it. Common brands are Moen, Delta, Kohler, and Pfister. If you can't find a name, take a photo to a hardware store or search online for "faucet identification" with your photo.
Can I replace just the washer instead of the whole stem?
Yes, but only on compression faucets. The washer is part of the stem, so you unscrew it, replace it, and screw it back on. On cartridge and ball faucets, you must replace the entire cartridge or ball assembly—there is no separate washer to replace.
What if water still leaks after I replace the stem?
Check that the packing nut or collar is tight enough—hand-tight plus a quarter turn with the wrench. If it's tight and still leaks, the valve seat may be damaged and need replacement. This is a job for a plumber unless you have a seat wrench and replacement in your kit.