Hi, You mean these things? http://www.yachtsurvey.com/boatreviews/Viking43-6.JPG I would say that if the Gate Valves were not swung regularly , you would be very lucky in an emergency to get them open at the first attempt. One thing to be very carefully considered with this system is the need to make sure the strainers used to protect the engine are correctly sized to make sure there is no fouling of the coolers. The newer CATS with Plate Coolers have very small orifices and the Main Sea Strainers need to have a 2.5mm mesh, the emergency bilge suction should be no more than this. It should also be noted that if using this sort of suction in an emergency it is very important that an eye is kept on it so when it starts sucking air the suction can be flipped back to Sea Water to protect the pump against dry running and or a potential loss of prime.