Repairing Delta sink faucets is an easy job that most people can easily handle. The single handle Delta faucets use a ball valve with spring-loaded rubber seats pressing against a ball with holes in it that control the flow of water by which hole(s) and how much of the hole(s) are lined up with the opening in the seat. A lever moves the ball controlling the position of the holes against the seat. The two handle Delta faucets have a stem with a disc on the bottom that has a hole in the disc. Turning the disc controls how much of the hole lines up with the hole in the spring-loaded rubber seat controlling the amount of water flowing through the hole. Delta Faucets are workhorses with an exceptionally long service life and in most cases a simple parts replacement has them ready to go for many more years. Most Delta faucets are still working well when they are replaced for a worn out finish after many years of service.
To repair a single handle sink valve will in most cases require a Delta #RP61 cam and packing, #RP70 ball, and a #RP4993 seat and spring kit. You will need an Allen Wrench to remove the handle, an Adjustable Wrench to remove the cap, a hook pick to remove the rubber seats and springs, and you will also want a small Phillips Screwdriver to help insert the seat and springs in place. Shut off water to the faucet you are repairing and verify the water is off. Place a rag over the drain to prevent parts from falling in the drain. Use the Allen Wrench to loosen the setscrew holding the handle on. After removing the handle use the Adjustable Wrench to remove the Cap from the valve. Take off the cam and packing then lift the ball out of the valve body. Note how the ball is located in place by a pin on the valve body and a slot in the ball. Take care not to damage the pin as it may ruin the faucet. After the ball is removed you can see down into the valve body where the seats and springs are located. Use a Hook Pick to pull out the seats and springs. You should then slid the new seat and spring onto the shaft of the Phillips Screwdriver so they are facing in the right direction that they can slide off the Screwdriver shaft into place. Holding the seat and spring in place on the Screwdriver shaft with your forefinger place the Screwdriver into the hole where the seat and spring go pushing them into place with your finger tip doing this with both the hot and cold seats. Put the ball in place lined up on the pin place the cam and packing on top of the ball with the locator tab in the slot on the side of the valve body. Place the cap back on and thread it in place securing it by tightening with the adjustable wrench. Then adjust the packing adjustment nut. Put the handle back in place securing it by tightening the setscrew onto the flat portion of the ball stem. Turn on the water supply and test the faucet.
To repair a two handle Delta faucet you will in most case need two each Delta #RP1740 or, #RP24096 stems and #RP4993 seats and springs. You will also need a Phillips Screwdriver, Adjustable Wrench, Knife, Plumbers Grease and a Hook Pick for tools. Cover the drain with a rag to prevent parts from falling in the drain. Use a Knife to pry off the caps on the top of the handles. After removing the caps use the Phillips Screwdriver to unscrew the screws holding the handles on and remove the handles. Look at the existing stems under the handle and note the location of the triangular handle stop sticking upward from the stem above the nut. You want to make sure the stops end up in the same location as they presently are, because if the orientation is switched the handles will operate in reverse. I usually take them out and place them on each side facing in the correct direction. Using the adjustable wrench unscrew the bonnet nut then grasp the stem and pull it out of the valve body. This exposes the seat and spring so they can be pulled out with the pick. You can then use the screwdriver to load the new seat and spring into place you probably will not fit a finger into this hole so find something to push them down into place. Apply Plumbers Grease to the o-ring on the new stem and push it into place making sure the stop is orientated correctly. When it is fully seated screw down the bonnet nut, replace the handle, screwing down the handle and replacing the cap. Repeat for the other side and then turn the water back on and test for leaks and proper operation.