Overflow box help needed

[Max In Montreal]

Hello all. long time lurker...first post in over 10 years...here goes...

Purchased a new to me 10 foot by 2 by 2 tank. One of the sides is drilled for 2 inch bulkheads. 2 holes near the top and one hole near the bottom. Lets forget the bottom hole. Both bulkheads are hard plumbed with 2 inch PVC and lead into a 130 gallon sump right under. 2500 gph pump returns the water tp the top of the tank by 1 inch PVC that is eventually split in 2. The whole system is working fine, but there was one last piece that was delivered today, my overflow box. The box is about 21 inches wide by 4 inches and about 7 inches high. It has teeth on the top to prevent fish from falling in. The box was purchased from Modular Marine... Excellent work and value...

My question is...when installing the box, how much room should I leave between the top of the box and the top tank frame?

 

[fishguy1978]

 

[Max In Montreal]

OH sorry I thought I explained it well.

 

[fishguy1978]

OH sorry I thought I explained it well.

Yes, but a picture is worth a thousand words and even the best written explanation is made even clearer by pictures. We also are not that literate so pictures are absolutely necessary. ?

 

[M1A1]

Seems like the other important part you left out is whether that tank is eurobraced, rimless, or something in between. Ultimately you need to be able to reach into the bottom of the overflow so how much room you need to leave - and how low your water level will be - depends on what access you have from above.

 

[Max In Montreal]

It is eurobraced. I decided to leave a little more than 1/4 of an inch. I drilled it and it is installed and running fine. This is my first time doing this and I thought I calculated everything...sigh... I should have asked for the box to be a little wider as now I have no room to slide in one 2 inch 90 degree elbow...pictures coming... let me resize them...

 

[duanes]

If using an overflow box with weirs, there would be no need to use elbows.
That said........ if using elbows there is no need for the overflow box.
Some examples......

Sometimes carve weirs into PVC

Sometimes I just allow water to flow thru the bulkhead openings drilled on the back, no weirs, no elbows.

The shot above is the back of the tank. Below the other side of the bulkhead, from the above shot, the bulkhead without an elbow, and water simply flow thru it to the sump.

 

[Oughtsix]

When I recently installed the overflow box in my 180g tank I put a scrape piece of 3/8" plywood on top of the overflow box to space it down by 3/8" and keep it level to the top of the tank. With a 2" overflow pipe, 1.5" backup overflow pipe, 1.5" hard return plumbing supplying 5 x 1" tank inlets and running my Jebao DCP 20000 full blast ( 5283gph rated) the water reached about 3/4 of the way up the slot openings in my 18" x 4" overflow box. When I blocked off many of the slots in the overflow box the water went over the top of the overflow box and swamped the box which as taken care of by the 2" overflow pipe.

If something floats in and plugs a bunch of the slots in the overflow box I an confident that when the water rises the 3/8" gap between the box and the top of the tank will take care of the water without letting the tank overflow.



For the in tank PVC elbow overflow on our 35g hex I cut the notches at an angle to promote a swirling action like a toilet. I put the outside coarse media on to keep the fish out. They still got in the sump. So I put the coarse media inside the elbow too which keeps the fish out. The media inside the elbow also gave the water a path to follow down the pipe which stopped all the splashing sounds and made the overflow pretty much completely quiet.

The water jet is a siphon relief for the bottom return pipes.

 

[Max In Montreal]

My issue now it to make it all quiet... I can fit an elbow in there if i can find shorter bulkheads. I want the overflow to be HERBIE style...

 

[fishguy1978]

It is eurobraced. I decided to leave a little more than 1/4 of an inch. I drilled it and it is installed and running fine. This is my first time doing this and I thought I calculated everything...sigh... I should have asked for the box to be a little wider as now I have no room to slide in one 2 inch 90 degree elbow...pictures coming... let me resize them...View attachment 1441653View attachment 1441654View attachment 1441657View attachment 1441658View attachment 1441659View attachment 1441660

Your bulkheads are backwards. The flange and the gasket go on the inside and the thread portion and the nut go on the outside.