Ken, I think what Cjloong trying to say is that the pipe is there as an oveflow control. If the water level goes higher than the pipe, it'll drain down. That way the water level won't be too high when he doesn't want it to be.
When he needs the water level to be higher, he just attach the extra connector and the water won't flow out any more.
Cjloong, am I explaining right?
