The water would fill the bottom of 1 until it got to the level of the pipe that poured into 3 then it would fill 3 until the level of water in 3 got to the pipe that goes to 4. If, as the picture seems to show, there is no outlet to 4 then, the water in 3 would fill to the pipe that goes to 5. However, the end of that pipe appears to be blocked also. If those are accurate representations of the system and not due to sloppy drawing programming then 3 would continue to fill to overflowing. The water in 1 would never rise past that pipe to 3 unless it poured in from the faucet faster than it could escape through the pipe to 3. All the water would flow over the top of three and none would get into any of the other containers. On the other hand, if the apparent blockages were non existent then, 4 would fill to overflowing before water would flow into 5 or anywhere else.