advise on making overflow weir please.

[everpresentnoob]

I am FINALLY getting my wifes 150 gallon tank up and running. Or at least trying to, life keeps getting in the way.

Anyway, the last thing I need to do is remake the overflow weir as the previous owner removed it for some reason. its a corner mounted overflow with the bottom of the tank drilled. Tank is 48 long, 24 wide and 30 tall. My plan was to build the weir out of two panels of 1/4 inch glass cut 8 inches by 27 inches. Silicone them at a 90 degree angle and then silicone them into the tank. then on the tank side essentially laminate two pieces of 1/4 inch acrylic glued at a 90 degree angle that is slightly bigger than 8 inches and 29.75 inches tall.

My question now is, I have a return pump that can supposedly flow up to 1700 gpm. how do I calculate the size of teeth I need to cut into the acrylic for the water to pass through? I plan on it being slightly lower than the top rim of the tank just as a safety margin. I was thinking 1/4 inch wide gaps with 1/4 inch teeth between them. These would line essentially 16 inches of space across the top of the two 8 inch pieces of acrylic. I can easily make a jig to cut them on my router table. But Im sure there are factors or calculations that i am not thinking about here. Honestly Im kinda winging it....

Also to attach the acrylic to the glass, I was thinking a semi liberal layer of silicone on the glass and just press the acrylic to it and clamp for 24 hours? is there a better way?

 

[That Crusso Kid]

I am FINALLY getting my wifes 150 gallon tank up and running. Or at least trying to, life keeps getting in the way.

Anyway, the last thing I need to do is remake the overflow weir as the previous owner removed it for some reason. its a corner mounted overflow with the bottom of the tank drilled. Tank is 48 long, 24 wide and 30 tall. My plan was to build the weir out of two panels of 1/4 inch glass cut 8 inches by 27 inches. Silicone them at a 90 degree angle and then silicone them into the tank. then on the tank side essentially laminate two pieces of 1/4 inch acrylic glued at a 90 degree angle that is slightly bigger than 8 inches and 29.75 inches tall.

My question now is, I have a return pump that can supposedly flow up to 1700 gpm. how do I calculate the size of teeth I need to cut into the acrylic for the water to pass through? I plan on it being slightly lower than the top rim of the tank just as a safety margin. I was thinking 1/4 inch wide gaps with 1/4 inch teeth between them. These would line essentially 16 inches of space across the top of the two 8 inch pieces of acrylic. I can easily make a jig to cut them on my router table. But Im sure there are factors or calculations that i am not thinking about here. Honestly Im kinda winging it....

Also to attach the acrylic to the glass, I was thinking a semi liberal layer of silicone on the glass and just press the acrylic to it and clamp for 24 hours? is there a better way?

Congrats on getting the tank set up for your wife!

Something to give a little thought to is, instead building your own overflow, buying one. That is, of course, unless you like building your own things.

The company in the link below is a well-known and respected company. If the first overflow doesn't suit your needs then give them a call and I'm sure they'll be able to help you. The link to the company website is the second link.

Pardon Our Interruption...

https://modularmarine.com

 

[D.N.R.]

I have calculated 1.12" of water level rise at 1700gph with your 1/4" teeth using the francis formula. I have used an effective weir length of 8".
Due to water surface tension and algae buildup it'll probably be closer to 1.25".

What you should consider about the glass you want to use is that it will be subject to the same water pressure as the rest of the tank, as it is a full height overflow box. I would make it out of the same glass thickness as the rest of the tank.

Have you considered using a u-shaped PVC profile which you glue to the top of the overflow box? That way you could place the overflow comb or teeth in this profile. You could remove them for cleaning or replace them if a tooth breaks off.

You probably know that silicone and acrylic don't hold well. I have used innotec adheseal to glue my overflow comb back on, worked really good. I have found it at a pond supply store.

 

[UncommonSense]

Here’s the direction I went for a 6” acrylic tube center overflow; ~18.75” of total circumference…

The teeth were laser cut into the tube by a local plastic fabrication shop, quite nicely, I might add!

If I was going to do it again, (especially for a larger tank flowing >900-1,000gph) I’d increase the total width of the parallel bottom of the tooth by .50”-.100”, and increase the height of the top of the tooth by .250”-.500”….

Furthermore, I’d leave greater than .100” between each tooth! (The angled “saw tooth” profile weir performs better per-inch than a straight-tooth profile weir, as water levels rise higher up the teeth!)

 

[RocketEngineer]

Why go full height yet almost no length?

 

[BZOFIQ]

I did a 66" overflow on my 82" tank - love it!