It a water regulator for injecting water into the chamber, it works off of the pump pressure to add water to the chamber for low end and when the pressure goes up it then bypasses right into the waterbox itself, thats the reason that it mounted there... They do go bad all the time, go ride it and watch it, if it leaks order a new on from seadoo. Don't bother with trying to rebuild it. It has a sm bleed hole like a car water pump and when it goes bad it dumps out water thru the hole. Sometimes on 3 seaters they can leak so bad that they burn up the pistons from over drying the pipe and causing the cylinders to lean out way too much!