Your garbage disposal is connected to the sink drain by a metal flange. When it was installed, the plumber sealed the underside of the flange with plumbing putty before securing it. If that putty chips out, which can happen when the disposal is loose and vibrates a lot, it results in the garbage disposal leaking water, and you have to remove the disposal and the flange to apply more. You also have to remove the disposal to replace the garbage disposal gasket, which may also be worn out.
While the disposal is out, you have a golden opportunity to replace the splash guard, which is the rubber gasket with the triangular tabs that keeps water in the disposal while the unit is running. Splash guards harden over time, and they also get moldy, so if your disposal is more than a few years old, it's probably time to replace it.
How to Remove the Garbage Disposal
You have to disconnect the power and plumbing from the disposal before you can remove it. Most garbage disposal units are plugged into a wall outlet, and if so, you can simply pull the plug. Some units are hardwired, though, and to disconnect it, you need to turn off the breaker, remove the terminal cover from the unit and disconnect the wires.
If you have a dishwasher, the drain hose is connected to the side of the canister. You can usually remove the clamp with a screwdriver and simply pull this hose off. To disconnect the drain, unscrew the compression coupling holding the discharged tube to the P-trap and remove the tube. Now you're ready to remove the unit from its mounting bracket, but it's heavy, so you may want to support it with an inverted bucket first.
You may be able to free the unit from the bracket by turning it counterclockwise a quarter turn or you may have to push a tab on the collar with a screwdriver, depending on the model. When the unit is loose, lower it away from the flange and take it out of the cabinet.
Fixing a Garbage Disposal That's Leaking Water
Now that the disposal has been removed, you can remove the flange. Start by unscrewing and removing the three adjustment screws on the lower mounting ring to free the mounting ring, then pull the snap ring apart and remove it. This frees the backup flange and fiber gasket so you can slide them off.
Push up on the sink flange to free it from the sink and lift it out. Scrape off all loose plumbing putty from the flange and the sink, then apply fresh putty by rolling it into a rope and pushing it into the underside of the flange. Set the flange into the sink and secure it by reversing the procedure you used to remove it.
Replace the Fiber Gasket and Splash Guard
Before you put the mounting assembly back together, you should replace the garbage disposal gasket if it's worn out. If you have a garbage disposal with a removable splash guard, this is also a good time to replace it. Remove the old splash guard by pulling it off the mouth of the disposal and fit on a new one. If you have an Insinkerator model, use an Insinkerator 3-in rubber garbage disposal splash guard.
With the new components in place, you're ready to reassemble the mounting bracket and hang the disposal. Reconnect the drain and the dishwasher hose, then test the seal by covering the disposal opening with a stopper and filling the sink. No leaks? Go ahead and connect the power and test the unit.