Faucet leaks when water is turned on at the spout base. I took the set screw out of the back but can,t remove it to access the orings or seals

Step 1- Shut off water supply to your faucet.

Step 2- Use 1/8" allen wrench to remove handle from faucet.

Step 3- Next it has a retaining ring to loosen, they make a little spanner wrench to fit this in all complete rebuid kits. And then you are ready to loosen the collar.
To do this would be best to have a tool to grip the collar and not do damage to it. Some hardware stores carry rubber slip on's to fit on chanel locks pliers to avoid marking. Or if you have access to a strap wrench that will work.

Step 4- After collar removed, remove plastic cap and washer and ball. Seats and springs are located in valve bottom. Remove seats and springs with a small screw driver.

Step 5- Pull up spout to remove it to replace the o ring's on shaft. Also if it has a sprayer the diverter is in the base near the bottom. A little round brass diverter for sprayer.

Step 6-Install o rings for spout on base and diverter for sprayer if it has one. Plumbers grease will make install of spout easier to go back onto base. Now you can reinstall spout back onto base .

Step 7- Install new seat's and spring's with a small screw driver. Line screw driver to port and let spring and washer slide into place and press it gradually into place to seat in.

Step 8- Install new ball and notice that it has a groove in it to line up in valve.

Step 9- Install washer and plastic cap with slot in proper space.

Step 10- Install cap and tighten and adjust retaining ring to tighten up movement from spout from side to side. At this point you can turn water back on to make sure you have no leaks before tighting handle in place.

Step 11- Install handle and you're in business, and have rebuilt your very first faucet with knowledge to tackle the next plumbing project. Take your time and look closely how everything is put together, so you will know how it goes back together.

BALL-TYPE SINGLE-LEVER FAUCETS

• The single-handle faucet with a ball inside to control both hot and cold water may either leak at the spigot or at the handle. A handle leak is usually caused by improper adjusting-ring tension. Simply adjust the tension to stop the leak. Leaks at the handle can also result from a worn cam gasket. Dripping from the spigot is usually caused by worn spring-loaded, soft rubber seat assemblies.
  
  
• Parts for ball-type faucets are available in kits. Get the spring/seats kit for spigot leaks, or the complete kit for handle leaks. It may be advisable to use the complete kit to replace all working parts of the faucet at the same time. In any case, you'll need a kit containing the spanner/hex wrench for removing the handle (hex end) and turning the adjusting ring (spanner end).
  
  
• Without turning the water off, loosen the handle set screw. Slide the handle from its stem.
  
  
• For a handle leak, try using the spanner wrench to tighten the adjusting collar. Tighten it by turning the wrench and collar clockwise until the faucet doesn't leak when it is turned on and off. If the adjustment is too loose, the faucet will leak. If you turn it too tight, the handle will be hard to move. When the adjusting ring cannot be turned with the wrench, it is corroded. At this point, you will need to remove the cap to free the adjusting ring. (See next step.) You must turn the water off before removing the cap! Apply penetrating oil to the threads, remove the ring and clean all parts before reassembling.
  
  
• Install the seats. For faucet leaks at the spigot, you must install new rubber seats and springs. You must turn off the water to make this repair. Unscrew the chrome cap by turning it counterclockwise. If it won't turn easily, wrap electrical tape around the cap and turn it with pliers. The adjusting ring, which is threaded into the cap's center, will come off with it. For a seats/springs replacement, pull the ball up and out by its stem. The gasketed cam will come with it. Now you can locate the two rubber seats and springs inside the faucet body. Remove them with pliers or yours fingers and install the new ones. The springs go into the holes first, and the cupped sides of the seats fit over the springs.
  
  
• Service the ball. If the ball is dirty or coated with scale, clean it or replace it with a new one. Both plastic and brass balls are available, but use a plastic one if your home has hard water.
  
  
• Reassembly. Put the ball and cam back into the faucet with the slot in the side if the ball fitting over the pin in the faucet body. Then make sure the tab on the cam slips down into the notch in the body. Not aligning the tab and notch is the number one cause for a faucet leaking after it is repaired. Finally, screw on the cap and adjust the ring as described in Step 2. If a properly adjusted ball-type faucet leaks at the cap, the cam and gasket must be replaced.
  
  
• Swing spouts. If a single-lever ball faucet leaks at the base, you should replace the O-rings. Remove the spout-retaining parts, as well as the spout. Wrap the spout-retaining nut with electrical tape to protect it, and remove the nut with a wrench or pliers by turning counterclockwise. Remove the spout by pulling it up and side-to-side. One or more O-rings should now be exposed. Take the O-rings to your hardware or home center store to get matching O-rings for replacement. Clean any scale that appears on the spout base, faucet body, and the inside of the swinging spout. Install the new O-rings and reverse the steps above to reassemble the faucet.