Why I'm ditching my herbie style overflow

[asylumdown]

I think the return chamber/overflow water height relationship thing is a function of the herbie system in general, regardless of how you have it plumbed. I'm not a physicist at all, but in a 'normal' overflow, the overflow pipes always have more capacity to drain than the return pump can pump, do any added water to the system falls to the lowest point in the system (the return chamber). This adding more water to a normal system just increases the return chamber water level.

In a herbie, the draining capacity of the overflow pipes is throttled, so the height of the water in the overflow and return chamber become highly related variables. Basically, I think that the height of the water in the overflows (and thus the return chamber) becomes a function of the restricted rate of flow, and the total amount of water moving through the system. If you add more water, rather than "falling" to the lowest level like it would with a normal overflow, it gets "held" above the point where the flow is restricted. Essentially it means that you need an ATO that adds exactly the amount of water you need and no more, otherwise you risk slowly overfilling your tank.

[reefwars]

maybe i missed it but do you have standpipes in your overflows?? this would keep your height set ,your gatevalve fine tunes the rest to a syphon ,trying to tune a herbie wthout standpipes and just the overflow boxes is a losing battle imo.

[reefwars]

also if both drains run into the same pipe at the end, your safety feature of the herbie is useless as one drain shold never hold water un less its needed, and if by chance it was needed you wouldnt want your emergency to be blocked b y whatever is blocking your primary

[2pts]

I use a herbie system on my 6' tank.

Here are my particulars...

Tank has dual corner over flow boxes, both double drilled. Left side, I use one hole for my return pipe. Right side has my emergency drain.

Both sides submersed drains are plumbed exactly the same, same fittings, same length of pipes, everything. Under water they both have a 6" threaded pipe that connects to a threaded 1" tee. The tee has one 1" strainer horizontally, one 1" strainer vertically pointing up, the bottom is threaded into that 6" pipe.

Underneath the tank, all pipe is measured so that my true gate valve meets exactly in the middle. I did this so that the force of gravity from each side would be the same.

Height was a problem with my setup. My gate valve is actually lower than the top of my sump which sits on the floor of the adjacent closet. This means the draining water must travel up about 5" of height before draining into my sump. Both the emergency drain and the gate valve line are on seperate drain lines into the sump. Because of the height, I have to ensure my emergency drain always has a trickle of water moving through it, otherwise the water sitting in the dip would go stale and bad.

Because I am already slightly taxing my emergency drain, I use a fairly weak return pump. I have fully closed the gate valve to test the capacity of the emergency drain, which it handled.

I should add I use an ATO, but my sump system is 90 gallons total, when the ATO shuts off, the sensor is NOT fully submersed under water.