Most Likely Causes (Ranked)
Delta's signature design uses a rotating ball that sits on two spring-loaded rubber seats. These seats (small rubber cups) press against the ball to control flow. After 5-10 years, the rubber hardens, and the springs lose tension. This is the #1 Delta leak cause. The repair kit (RP4993) is $4-6 and fixes it in 15 minutes. This applies to all Delta ball-valve faucets (identifiable by the single handle with a dome-shaped cap underneath).
The stainless steel or plastic ball inside the valve wears at the inlet ports, creating grooves that prevent the seats from sealing. Plastic balls wear faster than stainless steel. If replacing the seats and springs doesn't stop the drip, the ball is the culprit. Replacement balls are $8-15 (stainless steel recommended).
Newer Delta faucets use the MultiChoice Universal cartridge (RP46074 for Monitor series) or a ceramic disc cartridge instead of a ball mechanism. These fail similarly to Moen cartridges — internal seals deteriorate from heat and minerals. Diamond Seal Technology cartridges use a diamond-coated ceramic disc that lasts longer but still eventually fails.
Delta faucets have O-rings at the cam assembly (under the dome cap), at the spout base, and at the ball stem. These dry out and crack from heat exposure. The cam washer and adjusting ring above the ball can also wear. Water leaks from under the handle or around the spout base.
The adjusting ring at the top of the ball mechanism controls how tightly the ball is held against the seats. If it loosens (from vibration or use), the ball can't press firmly enough to seal. Tightening the ring with the Delta adjusting ring tool may fix the leak without replacing parts.
How to Fix It
Replace Seats and Springs (Ball Faucets)
$4-6 DIY- 1Turn off both supply valves. Lift the handle and remove the set screw (Allen key, usually 1/8 inch).
- 2Unscrew the dome cap (the chrome piece under the handle). Remove the cam, cam washer, and ball.
- 3Use needle-nose pliers to pull the rubber seats and springs from the two inlet holes in the valve body.
- 4Drop new springs into the holes, press new rubber seats on top (flat side up, cupped around the spring).
- 5Reassemble: ball (slot aligns with tab in body), cam washer, cam (tab into slot), dome cap. Don't overtighten.
- 6The Delta repair kit RP4993 includes seats, springs, cam, and cam washer — everything you need.
Replace the Cartridge (Cartridge Faucets)
$20-35 DIY- 1Turn off water. Remove handle (set screw under the lever).
- 2Remove the bonnet nut. Pull the cartridge straight out.
- 3Delta RP46074 is the most common single-handle cartridge. RP25513 is for many bathroom models.
- 4Insert new cartridge (match orientation). Reassemble and test.
Tighten the Adjusting Ring
Free- 1Remove the handle and dome cap. The adjusting ring is the brass ring with notches on top.
- 2Use the Delta adjusting ring tool (or needle-nose pliers in the notches) to tighten clockwise until the handle operates smoothly without dripping.
- 3Replace the cam washer if it's flat or worn while you're in there.
When to Call a Professional
The Delta RP4993 repair kit is $4-6 — don't pay $20+ for a 'complete rebuild kit' that includes parts you don't need.
Delta's Diamond Seal Technology (used since ~2008) means the faucet contacts water through the cartridge, not the valve body. If you have this, there's no ball mechanism — it's a cartridge.
Don't confuse Delta and Peerless. Peerless is Delta's budget line — parts look similar but aren't always interchangeable.
How to Prevent It
Replace seats and springs every 5-7 years proactively ($5 and 15 minutes).
Don't slam the handle — smooth operation extends component life.
Keep the Allen key and RP4993 kit on hand — you'll need it again eventually.
Delta offers a lifetime warranty. Call 1-800-345-DELTA for free replacement parts.
Frequently Asked Questions
Remove the handle. If you see a chrome dome cap with a ball underneath, it's a ball faucet. If you see a bonnet nut with a cartridge inside, it's a cartridge faucet. Generally: dome cap = ball (older), no dome = cartridge (newer).
RP4993 includes seats, springs, cam, and washer — it's the complete kit. RP61 is just the seats and springs. Get the RP4993 for a few dollars more.
Yes — Delta provides free replacement parts for life. Call 1-800-345-DELTA with your faucet model. No receipt needed for cartridges and repair kits.
Start with the $5 seats-and-springs kit (RP4993). If that doesn't fix it, replace the ball ($10-15). Tighten the adjusting ring for handle looseness.