Yes, but outside of the tank...external overflow box.

Are you sure the way I have it doesn't have the same effect? I don't know, just asking. I mean, do you really know, because I sure as heck don't. I've never had a drilled tank before.

The gate valve is adjusted so that the tank's water level goes up a bit and covers the intakes so that they don't suck up air. It'd be using the whole tank as its own great big overflow box. If the tank water ever gets too high, the third overflow, the backup, will start draining the water.

I know it would work but what I'm not sure about if it's going to be quiet enough for my liking.

If it does make a bit of noise from air getting sucked in I suppose I could always put a reverse durso on the drain in the sump.

Your way won't work. If you put gate valve on all three of your lines, then even if only one of them gets clogged you will have a big puddle to clean up!! The point of the Herbie is to be able to use the gate valves to throttle down the drains so there is NO AIR in the drains making them silent (the other end needs to be under water in the sump too). The second drain is for when the first one clogs up, and it will.

It should work if I'm understanding your last drawing plus making an assumption. Plus a Herbies as not drawing air are silent.

All three of you bulkheads are drilled to the same height, and within the tank you have a 90° pointing up (assumption). The heights in the tank of B and the one on the right (connected to E) are the same, with 1 being higher than the other two. On 1 and Z you have no valve and is the backup.

Something that might take some playing. I was doing some experimenting with a Herbie in a 33g running with no overflow box, just a standpipe coming up in the corner from a 1" bulkhead in bottom of the tank. Was just using a little pump so flow was 230gph. I adjusted the valve so the water stayed at a steady height and ended up I had 2 7/8" of water above the top of the standpipe. Where the playing comes in is adjusting the standpipe so the final water level is where you want it.

The backup overflow doesn't have a gate valve though. And it's higher than the other two. If the first two get clogged up then the third backup overflow, unrestricted, will kick in.

That is correct. The backup overflow is higher than the other two. The backup drain line also doesn't have a gate valve and it's completely unrestricted.

Yeah, it will definitely take some playing with the pipe heights. I will not glue anything in place until I achieve the perfect height. And since the tank will be acting as the overflow I'm assuming that if the power goes out I'll need a larger sump to take up the additional water.

Increasing the size of my refuge and sump are in the works now. I saw some unusual tanks at Big Al's that might work. The sump will then be 25 gallons and the refuge 20. If my CorelDraw trail doesn't expire I'll try and post an updated diagram.

OK, the sump I had in mind might be too tall to be able to take the protein skimmer in and out if I needed to.

Since my sump won't be able to handle the water from the tank in the event of a power outtage, how large should my external overflows be?

In your drawing it looks like all your bulkheads are the same height. How are you going to get your backup overflow higher than the primary overflows without having to keep your entire tank water level much lower than the rim of the tank? You need to have quite a height difference between the backup drain and primary drain(s).

No, the backup overflow is higher. Regardless, I've decided to heed your advice, as the way I was going to do it would require a larger sump to take up access water in the event of a power outage.

Check out my next revision. Tell me if my overflow box sizes look OK in relation to the tank size.

OK, this will probably be my final revision...

I've added Herbie overflows and a larger refuge.

A - 3/4" overtop PVC return manifold
B - 1" bulkhead and strainer leading to external overflow box
C - 1" Herbie backup overflow drain
D - 1" Herbie drain and strainer
E - External glass overflow box
F - 1" Spaflex backup drain pipe (left)
G - 1" Spaflex drain pipe
H - 3/4" Spaflex return pipe
I - 1" Spalfex drain pipe (right)
J - 1" Spaflex backup drain pipe (right)
K - ½"gate valve teed off from return
L - ½" Spaflex refuge feed from return
M - 20-gallon glass refuge
N - refuge light
O - 1" drilled bulkhead/refuge overflow
P - 3/4" Spaflex refuge drain
Q - 3/4" Spalfex refuge backup drain
R - 20-gallon glass sump w/ large return area
S - Baffles more than 1" apart
T - Eheim 1262 return pump
U - AquaC EV-180 protein skimmer
V - Drain area with filter sock

* White pipes are dirty tank drain water

* Grey pipes are clean return water

* Pink pipes are backup only and won’t usually have water in them

http://i105.photobucket.com/albums/m...berry06/v6.jpg