Sink Sprays and Diverters

A kitchen sink spray has a spray head attached to a hose, which is connected to a diverter valve in the faucet body. When you squeeze the spray head handle, the diverter valve reroutes water from the faucet to the spray head hose.

If the flow is sluggish, make sure the hose isn't kinked.
Clean the aerator in the spray nozzle.
Continued sluggishness may indicate diverter valve problems.
Clean the valve or replace it.
If the spray head leaks, remove it from the hose and replace the washer.
For a leak at the faucet end of the hose, tighten the hose coupling.
If the hose itself leaks, it's probably cracked. Replace it.

Provided by: http://www.allabouthome.com/tips/plumbing/sinkspraysdiverters.html