240 gal hole issues

[classic-chassis]

I am about to order a 240 gal (72inx30inx26in tall) the glass will be 2 cm thick.
It will have a coener overflow box built from the same glass. i want to hard plumb a sump which means having the tank builder make a hole in the bottom corner when the overflow box is.
does this affect the integraty of a tank this size at all? should i double layer the bottom?
I know sweet FA about physics so i'm presuming the water pressure in the over flow box will be a lot less than the tank over all.
ideas and opinions please

 

[Orchid0]

I know nothing
but want to wish you luck
if that works out itll be wicked

 

[ikevi]

I know sweet FA about physics so i'm presuming the water pressure in the over flow box will be a lot less than the tank over all.
ideas and opinions please

I don't know what people do for drilled wholes and tank glass (or acrylic) thickness. I assume a professional would know.

I just have to say though that your presumption is wrong. (I am actually a physics Grad student.) At the bottom of the tank it in essence only depends upon how much water is above it. So yes if you keep your water levels really low in your overflow box, some pressure will be less. But most people I know don't have there overflow box too lower just because of noise issues. (So in other words the pressure you are are looking at for the hole is the mass of the water above the hole times gravity times surface area of the hole.)

(Now the bigger issue I would think is if the tank is acrylic vs glass.) Hopefully you are getting acrylic because at that size glass is a huge pain. IE with glass most of the holding strength is on the edges, while acrylic is all over. So glass is likely to need a thicker bottom first because of possible extra strain from the hole being taken out.

 

[classic-chassis]

^ but the overflow box has an outlet for the water and is sectioned off from the rest of the tank with 2cm braced glass. So if the return pump is switched of the level of water in the overflow box would be nil, while the level of water in the sump would be three quaters full, hence my presumption of the presure being less. if the return pump is switched off the presure in the bottom corner on the outside of the overflow box would be a lot as with the rest of the tank but inside the box it would be nil, no?
p.s it's glass, just to buy cell cast acryilic here is mega expensive. i am thinknig of double sheeting the bottom so it'll be 4cm.

 

[classic-chassis]

Bump, any other opinions please the builder is on my case, do i need to double layer the bottom because of a drilled hole in an strong braced overflow box. Cheers chaps.

 

[BushFishRox]

I would do a 1" or 2.54cm bottom and the rest at 2cm

 

[Hawaii Predator]

I would do a 1" or 2.54cm bottom and the rest at 2cm

 

[classic-chassis]

Next question, do you think i should have one overflow box in one back corner or two boxes in each back corner, both with 2in holes?
I suppose the return pipe being on the opposite side of the tank to the overflow box (if only one) will cause flow and stop any stagnant water collecting on one side.

 

[classic-chassis]

Bump, probably belongs in "set up" thread, but i've gone for a single overflow box. I'm going to have a 70gal sump with four chambers. The sump will be 2feet below the main tank so the return pump will be approximatly 50in below the water line. What kind of return pump should i be looking at?
should the return pipe be at the top, middle or bottom of the main tank?
Cheers for reading.

 

[Mattyou]

You should have 2 holes in each overflow, a small one for return water, a larger one for water heading to the sump. I would use 2 overflows and shoot for 1600-1800 gph minimum flow rate.