Internal Horizontal Overflow Input Needed

[Mr_Jarhead]

Tank is a standard 75 gallon glass aquarium 48" long. I am going to install an internal horizontal overflow (A. Calfo style). By the way the design rocks! I have a couple of design questions I would like some input on.

1. Should I run the overflow along the entire length of the aquarium and drill below the box for my return lines? Or should I leave a few inches on each side of the overflow for the returns.

2. How much space between the bottom rim of the trim (top of tank) should I leave when mounting the unit? Does the flow rate matter for this at all? If so it will be 1200 gph. I would like to have as little space as possible so the waterline is not visible (I don't have a full hood, nor do I want one. Worst case I guess I could buy some black trim of some kind to attach (glue perhaps) to the trim to make it larger and cover the waterline.

Thanks in advance!

 

[vanceny]

i installed mine running the entire length and was also faced with the dilema of where to put the return lines. In my original configuration I was planning on drilling just below the overflow for the returns. After drilling all my holes for closed loop and drain i decided that 8 holes in the back of a 90gal may be to much so i plan on running the return over the top over the center brace.

I spray painted all visible pvc with Krylon fusion paint to hide it from view. Now it can be barely seen, it just blends into the back ground. The back ground was painted with two colors, dark navy and royal blue to give it a sense of depth.

I guess if your not drilling for a closed loop and on a 70gal which is shorter I would put the returns on the sides of the overflow. i think its more difficult to contruct the overflow with the sides instead of using the tank walls for the side.

I set the height of the overflow to be 3/8" above the trim.

Vance

 

[BeanAnimal]

Run the entire length. Drill holes for the drains in the back of the tank and drill closed loop intakes under the overflow. You can return through holes also, but going over the top will work very well. I prefer the cl returns through oceans motions.

Make the overlfow the same level as the bottom of the trim. The water line will not be visible then.

Make sure the overflow is perfectly level so that the water sheets over it evenly.

You can get smoked or grey glass, but it does not matter, coraline will cover it soon enough anway.
Bean

 

[Lcattin]

I did the same on my 65 gallon. I drilled for 2 1" bulkheads 4" down from the top and then built the overflow box the full length of the tank. For the return I built a manifold out of 3/4" pvc with 4 outlets, 1 on each end and 2 on the front for the returns from the sump. Kinda works like return and CL at the same time. I think there are some pics in my gallery. I am in the process of setting up my 180 the same way to see how it works. Sure looks nice without any powerhead wires or hardware in the tank.

 

[Mr_Jarhead]

Looks nice, how much space did you leave from the top of the overflow glass and the tank trim?

 

[James11]

Good question, I'm wanting to do the same thing with my 29 gallon acrylic tank, keep the good info coming.

 

[gbtower]

The height of the water going over the overflow will definitely depend on the rate of water going over it. I went with 1/2" first and then increased it to 3/4", but that was because my overflow length was short (~12").

I don't know if there already is a calculator somewhere, but to guess what the height will be, try pumping some water into a bucket. Get the circumfrence and the flow rate and you may be able to extrapolate what your height will be (sorry, i don't know what my flow rate is).

 

[Lcattin]

I kept the top of the glass overflow even with the bottom of the tank trim. That kept the water level just about the trim so you can't see it in the glass. Going the full length of the tank keeps the water depth over the oflow very thin. Probably no more than 1/16". I am running a 900gpm pump and had to slow it down just a tad or the bulkheads got noisy sucking air. I slowed it down enough that I didn't get a flushing action and didn't have to use durso's on the back. I just plumbed it straight down to the sump with 90 degree elbows. Any more flow than that and I will have to install some Durso stand pipes on the rear of the bulkheads.

 

[Mr_Jarhead]

Thanks for all the input. I think I will go with the following:

Overflow running the full length of the tank with 1/8" between top of overflow glass and tank trim (the space just for safety's sake). I know this is over kill, but I will drill for 3 - 1.5" bulheads in the overflow that will easily keep the water lever down in the overflow to prevent the noise. I am going to drill 4 - 1" bulkheads for the returns below the overflow. I will use 2 pumps from the sump at 600gph each (true 600 at the head height). I will use 1 scwd off each pump to split the return lines into 2 bulkheads each. That should provide a good random wave type action in the tank.

Any tweaks, thoughts, additions, or criticism on the above layout?

 

[Mr_Jarhead]

Well I guess since nobody thinks any of it is a bad idea this is the way I will do it.

 

[BeanAnimal]

jarhead....

Just but the top of the overflow even with the bottom of the trim (or a 1/16 or so above it if you want). This will ensire that the water level is above the trim and can't be seen from the display side.

I would go ahead with the 3 bulkheads in the overflow, but cut them down to 1" (if you want to save space and money). Put down turned elbows on all 3 and ball valves on all 3. Cap the tops of all 3 (like an external durso) and thread in john guest valves. You can then tune them between free flow and siphon flow as needed.

I WOULD run a single return pump (how big is your sump?). and then use the 4 lower holes (make them 1.5") as CLOSED LOOP INTAKES. You can connect them together in pairs of (2) with elbows and drilled pipe if you want (to cut down on localized suction and protect the critters). These would feed (2) LARGE flow pumps like DARTS that feed OCEANS MOTIONS for over the rop returns.

In this way you can get one hell of a lot of flow.
You could also use (2) for CL intakes, 1 each for a dart, and then 1 each for a LEG of a leg of the oceans motions.

SCWDs sucks and don't live a long enough life, they rob a TON of flow in the form of mechanincal energy and are old news. The OMs are expensive... but worth every penny

I hope that helps....