What You Need to Know Before You Start
A Delta kitchen faucet cartridge is the part inside the faucet body that controls water flow and temperature when you move the handle. When it wears out, you get reduced pressure, leaks under the sink, or a handle that sticks. Replacing it yourself takes about 30 minutes and costs $15 to $50 for the cartridge — far less than a service call.
The cartridge sits behind your faucet handle. Delta makes several cartridge types, and you need the exact model for your faucet or the new one will not fit. The model number is stamped on the faucet body itself, usually on the underside or back. Write it down before you buy anything.
You do not need special tools. A flathead screwdriver, an adjustable wrench, and possibly a cartridge puller (a $10 tool from any hardware store) are all you need. If your faucet is still under warranty, check the paperwork first — some warranties cover cartridge replacement at no cost.
Key Takeaways
- Find your faucet model number on the faucet body itself, then order the matching Delta cartridge before you start work.
- Turn off the water supply under the sink and open the faucet to release pressure before you remove anything.
- The handle comes off first with a screwdriver, then the dome cap and collar, then the old cartridge slides or pulls out.
- Insert the new cartridge with the notch or tab aligned to the slot in the faucet body, or it will not turn on properly.
- Test for leaks under the sink before you close the cabinet, because a cartridge seated wrong will drip when ready.
Locate Your Model Number and Order the Right Cartridge
Open the cabinet under your sink and look at the faucet body. The model number is usually a four or five-digit code stamped or printed on the back or underside of the faucet, near where the water lines connect. It often starts with RP (for "replacement part"). Write it down exactly as it appears.
Go to a hardware store or search online for "Delta RP [your number]" — that is the cartridge you need. Do not guess or buy a generic cartridge. A cartridge made for a different Delta model will not fit the valve seat, and you will have to return it. The cartridge comes in a box with a small instruction sheet; keep that sheet nearby while you work.
If you cannot find the model number, take a photo of the faucet and bring it to the hardware store, or call Delta's customer service line (1-800-345-3358) with the photo. They can tell you the cartridge number from the faucet design.
Turn Off the Water and Remove the Handle
Look under the sink. You will see two water lines — one hot, one cold — connected to the faucet body with nuts. Turn the shutoff valve on each line clockwise until it stops. If you do not see shutoff valves, turn off the main water supply to the house.
Go back to the sink and turn the faucet handle to the on position. Let any remaining water drain out. This releases the pressure inside the faucet so the cartridge comes out cleanly.
Now look at the faucet handle. There is usually a small screw or set screw holding it on — often hidden under a decorative cap or plug. Use a flathead screwdriver to pry off any cap, then unscrew the handle screw. The handle will slide or lift straight off. Set it aside where you will not lose it.
Remove the Dome Cap and Collar
Below the handle, you will see a dome-shaped cap (sometimes called a bonnet or packing nut). This cap holds the cartridge in place. Use an adjustable wrench to turn it counterclockwise. It is hand-tight, so you should not need to force it — if it does not budge, make sure the water is truly off.
Once the dome cap is loose, unscrew it by hand and set it aside. Below it, you may see a metal collar or ring. If so, unscrew that too by hand. Some Delta faucets have both; some have only the dome cap. Remove whatever is there until you can see the cartridge body sticking up inside the faucet.
Pull Out the Old Cartridge
The cartridge looks like a cylinder with a flat top and a small notch or tab on one side. Grab it firmly and pull straight up. It should come out with steady pressure. If it is stuck, do not force it — you can crack the faucet body.
Instead, buy or borrow a cartridge puller from the hardware store. It is a two-pronged tool that hooks under the cartridge and pulls it straight up. Screw the puller onto the top of the cartridge, then turn the handle to pull the cartridge out. This takes the guesswork out and prevents damage.
Once the old cartridge is out, look inside the faucet body. You will see a slot or notch on one side of the opening. This is where the new cartridge's tab must align. Wipe the inside clean with a dry cloth.
Install the New Cartridge and Reassemble
Look at the new cartridge. It has a notch or tab on one side. Hold the cartridge so that notch lines up with the slot you saw inside the faucet body. This alignment is critical — if the cartridge is rotated even slightly, the handle will not work right.
Insert the cartridge straight down into the faucet body. Push it down firmly until it seats fully. You should feel it click or bottom out. Do not force it; it should slide in smoothly if the alignment is correct.
Now reassemble in reverse order. Screw the collar back on by hand (if your faucet has one), then screw the dome cap back on with the wrench. Turn it clockwise until it is snug — hand-tight is enough. Screw the handle screw back in and replace any decorative cap.
Turn the Water Back On and Test for Leaks
Turn the shutoff valves under the sink counterclockwise to turn the water back on. If you turned off the main supply, turn that back on now. Wait a few seconds for the lines to fill.
Go to the sink and turn the faucet handle on and off a few times. The water should flow smoothly and the handle should move without sticking. Check that hot and cold water both work. If the handle is hard to move or water does not flow, the cartridge may be rotated — turn off the water, remove the handle and dome cap, and rotate the cartridge one notch at a time until it works.
Look under the sink. Dry the area around the faucet body with a cloth, then watch for drips for a few minutes. A small drip from the dome cap is normal for the first few minutes as air bleeds out. If water is still dripping after 10 minutes, or if there is a steady leak from the faucet body itself, the cartridge is not seated properly. Turn off the water and reseat it.
Frequently Asked Questions
How do I know if my cartridge is actually bad?
A worn cartridge usually causes reduced water pressure, a handle that is hard to move, or a leak under the sink that gets worse over time. If you turn off the shutoff valves and the leak stops, the cartridge is the problem. If water still drips from the faucet spout after you close the shutoff valves, the cartridge is worn out and needs replacement.
What if the cartridge will not come out?
Mineral buildup or corrosion can lock a cartridge in place. Try soaking the top of the cartridge with white vinegar for 15 minutes to dissolve deposits, then try pulling again. If it still will not budge, use a cartridge puller — forcing it by hand can crack the faucet body and cost you a new faucet instead of just a cartridge.
Can I use a cartridge from a different faucet brand?
No. Cartridges are brand-specific and model-specific. A Moen or Kohler cartridge will not fit a Delta faucet, and even a cartridge from a different Delta model may not work. Always match the model number on your faucet to the cartridge you buy.
Why is my handle still stiff after I replaced the cartridge?
The cartridge may be rotated wrong. Turn off the water, remove the handle and dome cap, and rotate the cartridge one notch clockwise. Reassemble and test. Repeat until the handle moves smoothly. If it is still stiff after rotating through all positions, the new cartridge may be defective — return it and get a replacement.
Is there a warranty on the replacement cartridge?
Most Delta cartridges come with a five-year warranty against defects. Keep your receipt. If the cartridge fails within that time, you can return it to the store where you bought it for a replacement at no cost.