Overflow tank to tank

[Caps]

Good morning,

I ask for help to model the overflow tank of another tank. I have a net where some tanks discharge the overflow into another tank. Momentarily I put a rule that opens or closes the tube by checking the level. The timestep is 00:30h so when it is open, for 00:30h keep the tube open and completely discharge the tank. Obviously the reality is not simulated, as soon as the level is lowered, the fluid does not pass.

Do you have any possible solutions?