To remove a Delta round stem valve, first shut off the water supply to the house and turn the faucet on to flush out any remaining water. Assemble the necessary tools and materials, including towels, silicone paste, a Delta valve kit, a Philips screwdriver and a Delta valve spanner. Use a flat-blade screwdriver to remove the handle button, and set it aside. Locate and remove the screw that connects the handle to the faucet.
Carefully unscrew the faucet dome to avoid damaging the copper pipes and valve system. If the dome is difficult to remove, do not force it; instead, wrap a vinegar-soaked rag around it for 15 minutes to help dissolve any mineral deposits. Remove the dome's plastic cover and rubber washer to access the valve. Holding the ball valve by the stem, pull it from the faucet. Catch hold of the exposed cup and spring set using a Philips screwdriver or Delta valve tool, and carefully pull them free.
Complete these steps in reverse order to reassemble the unit. Use silicone paste to set the new parts in place, making sure that the parts you put in match the parts you took out. Ensure that the two holes in the ball are facing up, and then reassemble the washer and plastic cap. Apply silicone paste to the dome threads before setting the dome back in place.
Adjust the tension on the dome using a Delta valve spanner, and then orient and replace the handle. Turn on the water and test the assembly, making sure that it is functional and that there are no leaks. If the handle is not stable, re-adjust the collar inside the dome until it stays in place.