Steps:1. Shut off main water supply valve outside using the basin wrench (figure A).
2. Take the screwdriver and remove the screw holding on the shower knob. Pull off knob then remove the screws holding on the backing plate. Remove the backing plate (figure B)
3. Since the water control is reversed, you should be able to correct the problem by removing the valve stem and rotating it 180 degrees. Mark the top of the valve stem with a grease pencil so you have a starting reference point.
4. Pull out the retaining clip out locking the stem in place using needle-nose pliers (figure C).
5. Use the plastic socket supplied with the cartridge and an adjustable wrench to turn the cartridge valve and break the friction between it and the housing (Figure D).
6. Remove the plastic socket and pull out the cartridge valve with pliers.
7. Apply plumbers grease to the valve and O-rings, and reorient it 180 degrees from its former position
8. Reinstall the valve and retainer clip. Replace the backing plate and shower knob.
9. Turn water back on and test flow to make sure hot is on the left and cold is on the right.