2000 gal plywood sump

karimwassef

karimwassef

Active member
ok. I'll show the picture first:

<a href="http://s1062.photobucket.com/user/karimwassef/media/Designs/0_zpsm1gxhvvx.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/Designs/0_zpsm1gxhvvx.jpg" border="0" alt=" photo 0_zpsm1gxhvvx.jpg"/></a>

it's two tanks: 600 and 1400 gals.

the water level is 20"

the structure is 3/4" plywood with 2x12 frame (yes, I realize that it's supposed to go the other way, but I'm tight on space).

The large tank is frame by the wood structure on one side and the sunroom steel frame on the other. So it's squeezed into shape.

I also added two 2x4s in the middle to brace the center.

They're covered in 1/4" of 2 part epoxy.

will it hold?
 
It's hard to epoxy when there are too many joining interfaces. I considered running PVC pipe through the ends to create cross spans. I might do that instead of the 2x4 braces.
 
The joinery will be your biggest difficulty. How are you planning to actually build the tanks?


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I've built plywood tanks before. The joints are just wood glue and screws.
The acrylic soaks into the wood and forms a contiguous plastic surface.
 
I decided to use concrete block epoxied to the concrete floor to act as a permanent stop against the outside edges.

I also added a 1" stainless steel square tube all around the rim.

<a href="http://s1062.photobucket.com/user/karimwassef/media/Designs/0_zpsaoxyqyjs.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/Designs/0_zpsaoxyqyjs.jpg" border="0" alt=" photo 0_zpsaoxyqyjs.jpg"/></a>

I put a model (my size) to scale
 
When I built a large plywood tank years ago, I made and epoxied the main box with dual thicknesses of 3/4 ply. I then made a single 3/4 thick eurobrace top (think the top on an acrylic tank), epoxied it on all surfaces then screwed it down into the box and ran a bead of silicone in the top joint.
 
Was the top eurobrace plywood also? Or acrylic?

How wide was it?

In my case, I would have to make it of multiple sections... would it still be effective? Maybe use 2x4s to get the continuity of a single block or sandwitch two offset 1/2" plywood sheet sections to avoid the butt joint stress.
 
If you're going to epoxy bricks to the floor why not do a cement or cinderblock frame?


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To do it right, I'd need to use rebar and create a wood frame to pour concrete... since I'm making a wood frame, I might as well just epoxy that. :D
 
Last edited:
I would think with the 1" square tubing, if welded at the corners would be sufficient...especially if you went with 3/16" wall. Alternatively, you could do 2" angle iron, 3/16" thickness. Lay it over the top edge of the plywood like eurobrace would be. Then weld in flat stock across the span. 3/16" should have more then enough rigidity though either way you go
 
karimwassef said:
Was the top eurobrace plywood also? Or acrylic?

How wide was it?

In my case, I would have to make it of multiple sections... would it still be effective? Maybe use 2x4s to get the continuity of a single block or sandwitch two offset 1/2" plywood sheet sections to avoid the butt joint stress.
Click to expand...

Yes, eurobrace was a full sheet of plywood with cutouts. Footprint of the tank was essentially 4x8. Unless you're freakishly tall, the pictures suggest you'd be able to use a coupe of sheets with the 8' length across the sumps. Perhaps not necessary if you are going to reinforce the sides with blocks/cement. 2x12 will bow laterally though.
 
ca1ore said:
Yes, eurobrace was a full sheet of plywood with cutouts. Footprint of the tank was essentially 4x8. Unless you're freakishly tall, the pictures suggest you'd be able to use a coupe of sheets with the 8' length across the sumps. Perhaps not necessary if you are going to reinforce the sides with blocks/cement. 2x12 will bow laterally though.
Click to expand...

The big tank is 13' x 8' and made of 4 plywood sheets on the bottom.

Yes, the 2x12s are used in the wrong direction... but they're sandwiched against the framework of the room and the concrete block against the floor.

I'm expecting the 1" square tube brace to mitigate the bowing.
 
You're fine.
Could just do some 2x6" crossbraces if worried but you'll be good with the metal around it

My 860g plywood tank I eurobraced with 2x4's on sides and back and 2x6 on front(since I lean on it to get to bottom of tank) and the cross braced it with 2x6 and 2x4s on top of those as well. No deflection at all
 
As an engineer and not having done any actual calculations my gut says you're probably okay. My worry are the butt joints you've drawn in with the 2x12s. Use a full length one.
Better do a steel 'exoskeleton' like mentioned before with only the plywood.
I'd consider going that then just a large pond liner.
Not sure what would be more expensive, the liner or epoxy.


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Hmmm.. steel tube is more expensive than 2x12s, but maybe I can use less.

But since the plywood sheets would be butt-jointed, I would need twice as much plywood without the 2x12 frame. I think the wood with a single steel "brace" at the top and concrete "brakes" at the bottom is just cheaper.

Two part epoxy is not cheap, but I'll be buying it in 5 gallon drums for this project, so - probably have enough.
 
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