Release the pressure in the tank by slowly turning the tank's top handle to the left to loosen it.
Pull the sprayer handle straight up until it pops off.
Flip the handle upside down to use the tool built into the underside.
Insert the tool end of the handle into the plunger by lining up the notches and then turn to the left to remove the plunger.
Pull the small rubber diaphragm out by hand and then remove any dirt or debris either with your fingers or with a pair of tweezers
Place the diaphragm back in and then replace the plunger. Tighten the plunger with the tool built into the handle.
Slip the handle forks under the plunger until it clicks back into place.