Herbie Overflow Max Flow?

FlyPenFly

SPS Killer
I'm thinking about converting my maggie muffler setup to a herbie overflow.

Only problem is that the tank has just two holes drilled, a half inch and an inch. I would have to use hang on tank return. I plan to use a Lifegard customFlo for the return.

Before I do this, I read that it says to use the smaller hole as the main drain which in this case is only half an inch. What's the max flow through that assuming a straight pipe down?

Is that really strictly necessary to use the smaller hole in order to greatly reduce the chance of flooding?
 

ca1ore

Grizzled & Cynical
When you say 1/2 inch and 1 inch do you mean the actual diameter of the hole or the size bulkhead the hole will accommodate? I'd assume the latter? Though a 1/2 pipe is a bit small for the siphon it can work. Definitely use the larger one for the open channel.
 

Drae

RAIDER NATION!
You can drain a ton of water through a half inch pipe. Upwards of six to seven hundred gph with a full siphon.
 

FlyPenFly

SPS Killer
Any reason to not use a drain guard on both drains?

It seems that even on the dry/trickle drain, snails or fish could get in.
 

SGT_York

New member
You really need to use the smaller as the siphon line so it will continue to function if plugged. If you run the large pipe as your siphon the 1/2" open channel won't be low enough in the overflow to handle the flow, resulting in flooding. Using the 1/2" as the siphon places it lower in the overflow so it can handle more flow, generally 4-6" below the water line is sufficient, if it can't handle the flow lower the siphon pipe to increase pressure and thereby flow. If you use it at the top there just isn't enough space so you'll run a dry sump or flood.

Using a drain guard helps but restricts flow, not a major deal breaker but you'll just have to ensure the open channel works. A much better idea is to put a lid on your overflow allowing water in but keeping snails and light (algae) out of the guards (strainers).

Also buy the 3/4" or larger gate valve as the valves when open restrict a significant amount of flow. You'll get better flow with the larger gate and you can easily reuse it when you change tanks.
 

FlyPenFly

SPS Killer
Not sure what you mean by low enough in the overflow? I have a pipe cutter so I can make the drain pipes any height.
 

SGT_York

New member
The water above the opening is what creates the pressure to push water through the pipe the higher the level the greater the pressure/flow. If you use a small pipe as the dry the water level has to be higher than a larger pipe to generate the same amount of flow.

So if you have the large pipe as your emergency you can set it just under the display tank water. If you go with the smaller pipe the water will need to rise much higher which will flood your tank or dry out your sump, or it will require you to lower the overflow water level which creates noise.

Difficult subject to write very easy to actually see. A herbie should be no more than 6" below the display water level. Too low and you get noise from the water falling off the overflow. Too high and the water level in your display rises.
 

FlyPenFly

SPS Killer
Glad I asked, okay makes sense thanks.

I guess I'll be running the half inch.

I'm trying to decide between the DC6000, DC9000, and DC12,000. I guess I might have to go with the smallest although I plan to run a manifold system with 4 outlets (UV, reactor, frag tank, chiller). The head height will about 3.5 to 4 feet.

Is 600gph really possible on a half inch siphon?
 

ca1ore

Grizzled & Cynical
Not just whether the siphon will move 600 GPH, but whether the emergency can handle same should siphon clog. Answer is probably yes, couldn't hurt to test first though.
 

FlyPenFly

SPS Killer
One more question.

Since I have an Apex anyway, I'm going to run a float switch in the overflow to stop the return pump in case of a clog. Is there any reason to have float switches outside the overflow in the display tank?

I would imagine I'm going to drill 2 holes in the overflow cover for 2 switches as an extra measure of safety in case a switch gets stuck.
 
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