What You Need to Do Before You Start

Replacing a Delta faucet cartridge takes about 30 minutes and requires no special plumbing skills. The cartridge is the part inside your faucet that controls water temperature and flow—when it wears out, you'll notice the handle getting stiff, water leaking from the spout, or the temperature not adjusting smoothly. You can replace it yourself with basic tools you likely already have at home.

Before you begin, turn off the water supply to the faucet. Look under the sink for two shut-off valves (one for hot water, one for cold). Turn both clockwise until they stop. If you can't find them or they don't work, you'll need to shut off the main water supply to your house. Open the faucet handle to release any remaining water pressure in the lines.

Gather these tools: a flathead screwdriver, an adjustable wrench or pliers, a Phillips head screwdriver, and your Delta cartridge replacement kit (which includes the new cartridge and usually a cartridge puller tool). You can order the exact cartridge for your faucet model online or pick one up at a hardware store—bring your faucet model number, which is usually stamped on the faucet body or the box it came in.

Key Takeaways

  • Turn off the water supply under the sink before you remove any parts, and open the faucet to release pressure.
  • Remove the handle by prying off the decorative cap with a flathead screwdriver, then unscrew the handle screw underneath.
  • The cartridge sits under a collar nut that you loosen with an adjustable wrench—the cartridge puller tool that comes with your replacement kit makes removal easier.
  • Insert the new cartridge with the flat side facing the same direction as the old one, then reassemble the collar nut, handle, and cap in reverse order.
  • Turn the water back on slowly and test both hot and cold water before you consider the job finished.

Remove the Handle and Decorative Cap

Look at the top of your faucet handle. You'll see a small decorative cap—usually chrome, brass, or plastic—that covers the screw holding the handle in place. Use a flathead screwdriver to pry this cap straight up and off. Work slowly around the edges so you don't crack it. Set it aside somewhere safe.

Underneath the cap is a single screw. Use a Phillips head screwdriver to remove it completely. The handle will now slide straight off the faucet body. If it's stuck, wiggle it gently side to side as you pull—don't force it or you may crack the handle.

Loosen and Remove the Collar Nut

Once the handle is off, you'll see a large hexagonal nut (the collar nut) sitting on top of the faucet body. This nut holds the cartridge in place. Use an adjustable wrench or pliers to grip this nut and turn it counterclockwise. You don't need to remove it completely—just loosen it enough that you can unscrew it by hand. Turn it until it comes free and set it aside.

Some Delta faucets have a decorative collar or escutcheon (a ring-shaped piece) that sits under the nut. If yours has one, it will come off now. Keep track of the order you remove these pieces so you can put them back the same way.

Pull Out the Old Cartridge

Now you can see the cartridge itself—it looks like a small cylinder with a flat side and a rounded side. The cartridge puller tool that comes with your replacement kit has two metal prongs that grip the cartridge. Insert the prongs into the slots on top of the cartridge, then pull straight up with steady pressure. The cartridge should slide out. If it's stuck, wiggle the puller tool slightly side to side as you pull, but don't twist it.

If your kit didn't include a puller tool, you can sometimes grip the cartridge with pliers and pull straight up, but the puller tool is gentler on the cartridge housing and less likely to damage it. Once the old cartridge is out, look at which side is flat and which is rounded—you'll need to insert the new one the same way.

Insert the New Cartridge and Reassemble

Before you insert the new cartridge, rinse it under clean water to remove any debris or packing material. Align the flat side of the new cartridge with the flat side of the old one you just removed. This orientation matters—if you install it backwards, the hot and cold will be reversed. Slide the new cartridge straight down into the faucet body until it sits flush.

Now reverse the removal steps. Screw the collar nut back on by hand first, then tighten it with your wrench until it's snug—don't over-tighten or you may crack the cartridge. Replace any decorative collar or escutcheon that was there. Slide the handle back onto the faucet body and insert the handle screw. Tighten the screw with your Phillips head screwdriver, then snap the decorative cap back on top.

Turn the Water Back On and Test

Go back under the sink and slowly turn on both water shut-off valves. Turn them counterclockwise until they stop—don't force them. Open the faucet handle and let water run for 10 to 15 seconds to flush out any air in the lines. You may see some discolored water or air sputtering out; this is normal and will clear in a minute or two.

Test both the hot and cold water. The handle should move smoothly, and the water temperature should change when you move the handle from cold to hot. If the hot and cold are reversed, you installed the cartridge backwards—you'll need to remove it and flip it 180 degrees. If water is still leaking from the spout or the handle is stiff, the cartridge may not be seated properly; remove it and check that the faucet body is clean and free of debris before reinstalling.

Common Mistakes to Avoid

The most common error is forgetting to turn off the water before you start. Water will spray everywhere the moment you remove the collar nut, and you'll have a mess on your hands. Always shut off the valves under the sink first and open the faucet to release pressure.

The second mistake is installing the cartridge backwards. The flat side must face the same direction as the old one, or your hot and cold will be reversed. Take a photo of the old cartridge before you remove it if you're unsure.

A third mistake is over-tightening the collar nut. The cartridge is made of plastic and ceramic, and too much pressure can crack it. Tighten until snug, then stop—you should be able to turn the nut with your fingers before you use the wrench.

Frequently Asked Questions

How do I know which Delta cartridge to order?

Look for the model number on your faucet body or the original box. It's usually a number like RP19804 or RP25804. Search that number online or take a photo to a hardware store—they can match it to the correct cartridge. Ordering the wrong cartridge means a wasted trip and more time without hot water.

What if the cartridge won't come out even with the puller tool?

The cartridge may be stuck due to mineral buildup. Try soaking the area around the cartridge with white vinegar for 15 to 20 minutes to dissolve deposits, then try again. If it's still stuck, explore penetrating oil (like WD-40) and wait an hour before trying. Never force it or you may crack the faucet body.

Can I reuse the old collar nut and handle?

Yes. The collar nut, handle, and decorative cap are reusable. Only the cartridge itself wears out and needs replacement. Keep all the old parts in case you need them later.

Why is my water still leaking after I replaced the cartridge?

The most common cause is the cartridge not being seated all the way down. Remove it, clean the faucet body with a cloth to remove any debris, and reinstall it. Make sure it slides all the way in until it stops. If it still leaks, the new cartridge may be defective—contact the manufacturer or return it for a replacement.

Do I need to turn off the main water supply if I can't find the shut-off valves?

Yes. If the shut-off valves under the sink are missing or don't work, you'll need to shut off the main water supply to your house. This is usually a valve near your water meter or where the main line enters your home. Turn it clockwise until it stops, then open a faucet to release pressure before you start the cartridge replacement.