Fluid Dynamics Question

[wardworld]

Thought I might see if anyone has any ideas about this:
Working on the Herbie overflow for my new tank - that's the one with a gate valve placed on each drain to control the level of each overflow.

I will bring the two returns under my tank, then add an elbow for the pipe to feed from there to a T which will then run one pipe out through a wall to drain into the sump.

My question, instead of having a gate valve under both overflows, can I use one gate valve after the T to regulate the water in the overflows???
Thanks,

[Jefe12234]

No, the Herbie method depends on having one restricted drain and one unrestricted backup drain. If you place the valve after the drains have merged, then you're restricting both drains.

Also, you want a valve on only one drain, not both.

[wardworld]

I apologize for not being clear: I have 2 drains in EACH overflow. One is the main drain per overflow and one is the emergency drain in each overflow. What I'm wondering is if the gate valve after the T will effectively control the levels in both overflows (again, each overflow has its own emergency overflow, totaling 2 for the tank).
Thanks,

[Jefe12234]

Oh, ok. In that case I think it would be preferable to have one valve after the tee. It will keep the water level in the overflows even. If you used two valves, I think you'd be constantly struggling to match the overflow levels.

Are the returns going to bulkheads on the back of the tank then since you'll be using all the bulkheads in the overflows as drains?

[wardworld]

Yes, actually the returns on coming in OVER the top of the tank (mounted to the wall) and, using loc-line, shooting into the tank.