DIY AIO weir sizing and options

[DeepDiver]

R2R’ers,
I’m going to fabricate an in tank filtration for my 75g, essentially a AIO. I’m going to use black 1/4 acrylic. I have a few questions.
- I’m coming up with 8 1/4in slots for the weir to support 500gph. Does that sound right?
- Are the ‘teeth’ really needed it is just a ledge OK?
- I’m showing two returns but a single return, at the higher position, with a randomizer would be better. Any thoughts?


Thanks,
DD

 

[jsker]

Let's get you some help.

#reefsquad

 

[JoshH]

How wide is the actual overflow in inches? Sorry having a hard time reading the writing.

 

[DeepDiver]

@JoshH - 8in width for the first chamber. The scale for the drawings 2in per line. I am planning on 500gph, this will be FOWLR . If my math is right on the flow rates I could reduce that to give me more room in the rest of the filter. Or I could make the filter smaller.
The notes on the drawing say 8 1/8in slots. At 1in high that should flow 700gph +. If I go with 1/4in slots that should give me plenty of reserve in case one or two get blocked.
Yes, my hand writing sucks.

DD

 

[DeepDiver]

So it maybe more helpful to do a quick overview of how I did the flow rate math. Eight 1/4 x 1 in slots gives 2 square inches of flow area. This is the equivalent area of 1.25in pipe, which will flow 1500gph. Because there is a lot more water in contact with the pvc I assumed 50% friction loss, giving me 750gph.

DD

 

[JoshH]

I would say you are 100% fine with that plan, if you do 1/4" slots with 1/4" teeth that equals 12 slots over 6 inches leaving 1 inch on either side. Which should flow 700 GPH with no issues. Keep in mind that ideally you only want 1/2" - 3/4" of water height flowing over the weir if they are only 1" high which it looks like you've thought about in advance.

 

[Chuk]

How high are your slots? If I'm doing the math correctly at 8 slots 1/4" wide the height through each tooth would be approximately 1" for 500 gph (~8 gpm) of flow. If your slots aren't at least that high just go with a straight weir the teeth wont be doing anything for you. You could add more teeth or widen the slot to get the water height down.