Delta kitchen faucets leak for one of three reasons, and the location of the leak tells you exactly which one it is. Water dripping from the spout means the cartridge is worn or the seals inside the cartridge have failed. Water leaking from the base of the handle means the O-rings on the cartridge body or the bonnet nut have dried out. Water leaking from the base of the faucet body where it meets the sink means the deck seal or the supply line connections have failed. A Delta faucet does not use compression washers like an old two-handle bathroom faucet. It uses a cartridge that contains all the moving parts and all the seals in a single replaceable unit, and replacing that cartridge fixes the vast majority of Delta faucet leaks in about thirty minutes.
Delta faucet cartridges are warrantied for life. If you call Delta customer service and describe the problem, they will mail you a replacement cartridge for free. You do not need to provide a receipt, a proof of purchase, or the original packaging. The lifetime warranty is the reason Delta faucets are worth repairing instead of replacing. A new cartridge costs about thirty to fifty dollars if you buy it at a hardware store. It costs nothing from Delta. The difference is about a week of shipping time versus a trip to the store. If the faucet is leaking and you need it fixed today, buy the cartridge. If you can wait, call Delta.
Diagnose the Leak Before You Take Anything Apart
Turn the faucet on and watch where the water comes from. A drip from the end of the spout that continues after the handle is turned off means the cartridge is not sealing completely. A leak that appears around the base of the handle only when the faucet is running means the O-rings on the outside of the cartridge are worn. A leak that appears at the base of the faucet body, where the faucet meets the sink or the countertop, means the flexible supply lines or the deck gasket underneath the faucet are leaking, not the cartridge.
Determine which Delta cartridge your faucet uses. Delta has used several different cartridge designs over the years, and the replacement must match. The easiest method is to find the model number of the faucet, which is typically printed on a tag attached to one of the supply lines under the sink, and enter it on Delta’s website. The website will show the correct cartridge part number. If you cannot find the model number, remove the handle and take a photo of the cartridge. The parts diagram on Delta’s website will help you identify it by appearance. The most common Delta kitchen faucet cartridge is the RP50587 for single-handle faucets with the diamond seal technology, recognizable by the blue plastic body and the diamond-shaped logo on the top of the stem.
Replacing a Delta Single-Handle Kitchen Faucet Cartridge
Turn off the water supply valves under the sink. Turn the faucet on to release pressure and confirm the water is off. Close the drain stopper or cover the drain with a rag. The small parts you are about to remove will find the drain if it is open.
Locate the set screw that holds the handle in place. On most Delta kitchen faucets, the set screw is on the back of the handle, facing away from you, accessible with a hex key. The hex key size is typically three-thirty-seconds of an inch or two and a half millimeters, and Delta often includes the correct hex key with the replacement cartridge. Loosen the set screw and pull the handle straight up off the faucet body. If the handle is stuck, wiggle it gently while pulling. Do not pry against the faucet body with a screwdriver. The chrome finish scratches easily and deeply.
Remove the bonnet nut, the large threaded ring that secures the cartridge in the faucet body. The bonnet nut may be covered by a decorative ring that unscrews by hand. Turn the bonnet nut counterclockwise with an adjustable wrench. If it is stuck, wrap a rag around the wrench jaws to protect the finish. Lift the bonnet nut off and set it aside. Underneath it, you will see the top of the cartridge with the stem protruding.
Grip the stem of the cartridge with pliers and pull straight up. The cartridge is held in place by O-rings that create a tight friction fit. It will resist. Pull firmly and evenly. Do not twist. Do not pry from the side. A cartridge removal tool, which is a plastic cap that threads onto the cartridge stem and provides a handle to pull, is available from Delta for a few dollars and makes removal substantially easier. If you damage the faucet body while prying out a stuck cartridge, the entire faucet must be replaced.
Inspect the inside of the faucet body with a flashlight. The valve seats, the round openings where water enters the cartridge, should be smooth and free of debris. Mineral deposits can be cleaned with a soft cloth and white vinegar. Do not use an abrasive pad or a metal tool to scrape the valve seats. Scratches in the seats will prevent the new cartridge from sealing. Insert the new cartridge, aligning the tabs on the cartridge body with the slots in the faucet body. The cartridge should drop into place with firm hand pressure. If it does not seat fully, check the alignment of the tabs and try again. Do not force it.
Reinstall the bonnet nut and tighten it by hand, then an additional quarter turn with the wrench. Overtightening the bonnet nut crushes the O-rings and causes the faucet to be stiff or to leak from the handle base. Reinstall the handle, tighten the set screw, and turn the water supply valves back on. Run the faucet for a minute to flush any debris from the new cartridge, then check for leaks at the handle base and at the spout.
Fixing Leaks at the Handle Base and the Faucet Base
If water leaks from the base of the handle even after replacing the cartridge, the O-rings on the outside of the cartridge body or the O-ring under the bonnet nut are the problem. The cartridge replacement kit typically includes these O-rings. Remove the handle and the bonnet nut. Use a pick or a small flathead screwdriver to lift the old O-rings off the cartridge body and out of the groove inside the bonnet nut. Coat the new O-rings with a thin film of silicone plumber’s grease, which comes with the replacement cartridge kit. Install the new O-rings in the same positions. Reassemble the faucet. The grease lubricates the O-rings so they slide instead of bind, and it prevents them from drying out.
If water leaks from the base of the faucet body where it meets the sink, the problem is the deck seal, the O-rings on the supply line connections underneath the sink, or a crack in the supply lines themselves. Check under the sink with a flashlight while the faucet is running. A leak at the supply line connection to the faucet body can be fixed by tightening the connection nut slightly. A leak in the middle of the supply line requires replacing the supply line, which on a Delta faucet with integrated supply lines means replacing the entire faucet because the supply lines are permanently attached. Delta’s lifetime warranty covers this. A leak at the deck gasket, the seal between the faucet base and the sink, requires removing the faucet from the sink and replacing the gasket, which Delta will also provide under warranty.
FAQ — Fixing a Leaky Delta Kitchen Faucet
My Delta kitchen faucet has a ball and socket instead of a cartridge. How do I fix it?
Older Delta kitchen faucets use a ball-and-socket mechanism where a slotted metal ball rotates in a socket with spring-loaded rubber seats. The ball is controlled by a handle that moves in all directions. These faucets leak from worn rubber seats and springs, which are located under the ball. Replacement kits include the ball, two seats, and two springs, and cost about fifteen dollars. The repair is similar to a cartridge replacement: remove the handle, unscrew the cap, lift out the ball, replace the seats and springs with the new ones, install the new ball, and reassemble. The seats and springs are small and easily dropped. Work over a towel covering the drain.
After replacing the cartridge, the handle is very stiff. What went wrong?
The bonnet nut is too tight. Loosen it an eighth of a turn at a time until the handle moves smoothly. If loosening the bonnet nut causes a leak at the handle base, the O-ring under the bonnet nut is pinched or missing. The second cause is that the replacement cartridge is the wrong model. A cartridge that is dimensionally correct but has a different internal design will fit but will not operate smoothly. Verify the part number before installing.
My Delta kitchen faucet has two handles. Does this repair guide apply?
No. A two-handle Delta kitchen faucet uses traditional compression stems with rubber washers, similar to a two-handle bathroom faucet. The repair involves removing the handle, unscrewing the stem, and replacing the seat washer at the bottom of the stem and the O-ring on the stem body. Delta two-handle kitchen faucets are less common than single-handle models, but the repair parts are available under the same lifetime warranty.
Last modified: June 13, 2026
