DIY - Projects & Ideas • Plywood Tank 250gallon

[Coln]

That's the first time I've used epoxy and would use west again the stuff is easy to use unless all epoxy is the same but I doubt it.
Colouring the last coats is the way to see what you've coated

[I3lazd]

did you fiberglass it as well or just epoxy?

[Coln]

Yes, the base I used thick fibreglass from a mate that was for roofs so took a lot of epoxy but
with the weight of rocks will need to be super strong.
The walls have a thin layer but always better to have fibreglass in the epoxy makes it
a lot stronger

[Coln]

Assembled tank today everything fitted well when bolted up, screwed rod was good for various lengths and easy to cut in the vice. Gonna coat front panel again as screw holes look coated
but are not final coat black. On holiday for a week now so hope to get blocks built and last coat of epoxy and start planning for change over....

[Coln]

Blocks finished today, hope to move existing tank down next weekend and take old blocks down
to new level then start assembling tank

[auratum]

Cobain - this looks really nice, but I have a concern about the back corners with respect to strength. The concern is due to the way that the side is connected to the back. I could be wrong, but from the pictures it looks like all the strength in the back corner is coming from the shear strength of the plywood. It would have been better to extend the framing of the side wall all the way to the back corner and then tied that into the back wall. From the picture, it looks like the side piece bolted to the back wall through the plywood is not connected to the rest of the framing for the side wall - that is the apparent weak point. If you replace that piece with two 2x4’s or a 4x4 and bolt or screw it to both the side and the back then it will increase the strength significantly for these back corners.

The way it appears to be built from the picture could allow outward pressure on the side wall to shear the plywood at the back wall – causing a failure at the back corner. You have the added benefit of the fiberglass strength, but if it were me, I would change how you tied the back corners together.

Good luck with your build - it is coming along nicely!
Patrick

[scottiefish]

i agree with auratum. it looks super, but the corner may be an issue. go with the 4 by 4 in the corners and bolt it to the sides and the back. cant wait to see more!

[I3lazd]

I agree he shouldn't have cut the 2x4 off at the end, he should have left them so he could bolt a 4x4 into the bottom and bolt in from both sides of his support beams.

[Coln]

Thanks for input guys, the plywood is fixed with flooring screws and glued to all the 4x2 and the end piece of 4x2is screwed thru the plywood and thru the end post of the side panel.
It's totally solid as the 3 bolts that hold panels together each corner are used to hold big roof trusses together. I also plan to put metal supports on top of the panels at corners and further in to start anyway, pics of screws and glue

[I3lazd]

If you mad that minor adjustment it would mean a world of diff. in support and be an easy and cheap fix. Just my 2 cents though.

[Morpheus]

I think it will be fine. The key is he said he screwed and glued the the 2 x 4 on the end frame into the cut down 2 x 4. For the tank to fail, it's going to have to have enough pressure on the back to pull those screws out, bend the screws that go through the plywood into the back frame, bend the screws in the cut down 2 x 4, break all the glue free, and bend some seriously big (3/4"?) thick bolts. Not to mention the fiber glass on the inside of the tank.

[Mcdaphnia]

If you mad that minor adjustment it would mean a world of diff. in support and be an easy and cheap fix. Just my 2 cents though.

I for one cent worth don't agree. At least not in the direction an adjustment might take. This tank is not so tall that it really needs any of the 2 by 4 ribbing at all. I've built 42" tall tanks over 500 gallons with out any ribbing, just plywood screwed together and never had any leaking or bowing problems. It looks solid as is, though if the ribbing had continued out to the ends of the walls, it would have looked tighter. A nylon strapping band just in front of the seam over and under the tank would do more than a 4 by 4 to keep the plywood from deflecting, which it probably would not at this water pressure. A 4 by 4 however introduces complications, from whether or not is is safe for interior use, to the tendency of 4 by lumber to twist and bow, taking the plywood with it.

[I3lazd]

updates???

[Coln]

Have built second block wall and taken original down to new level.
Planning to assemble tank in position on friday and fill on sunday.
That will be the moment of truth, will post on sunday pm my time.
Pic of the left side background in progress
How's your tank going?

[auratum]

If you made that minor adjustment it would mean a world of diff. in support and be an easy and cheap fix. Just my 2 cents though.

I for one cent worth don't agree. At least not in the direction an adjustment might take. This tank is not so tall that it really needs any of the 2 by 4 ribbing at all. I've built 42" tall tanks over 500 gallons with out any ribbing, just plywood screwed together and never had any leaking or bowing problems. It looks solid as is, though if the ribbing had continued out to the ends of the walls, it would have looked tighter. A nylon strapping band just in front of the seam over and under the tank would do more than a 4 by 4 to keep the plywood from deflecting, which it probably would not at this water pressure. A 4 by 4 however introduces complications, from whether or not is is safe for interior use, to the tendency of 4 by lumber to twist and bow, taking the plywood with it.

I stand corrected then. Nice build & nice brick work! Looking good!