15 minutes.
Don't worry about the water.
Keep eyewashes and showers clear of clutter.
EYEWASH - something in your eye, wash for 15 minutes. Remember not all solvents are water soluble and it may take some time to wash the material out thoroughly.
SAFETY SHOWER - Remove clothing & wash for 15 minutes. Phenol in particular acts as an anesthetic and you can't tell it's burning through your flesh. [This has happened at HMS, NOT pretty]
Eyewashes and safety showers are checked at regular intervals, however, it is best to let them flush for a few seconds before using, as rust can build up in pipes.