Why would a kitchen faucet turn itself on when using the washer or outside faucets?

The kitchen faucet tap is threaded and is kept stationary by an upward force from the water supply. A sudden surge of pressure from somewhere else in the pipeline releases the pressure on the tap allowing the tap to move freely. While there is still a little pressure remaining on the tap it will of course take the path of least resistance and open up a little. This seems to happen more frequently as the tap threads continue to wear. Wow that answer above??? My guess is that you have a Moen faucet they are known to do this when subjected to high line pressures and the pressure fluctuates. Check your line pressure with a gauge it should be 80 psi or less or you need a pressure reducing valve installed. The faucet probably needs the cartridge replaced. == Answer== The delta two handle faucet will do the samething. And i think any washerless faucet could do it. Replace seats, spings and cartridges.