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WP's 55gal to 270gal plywood tank conversion

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83K views 216 replies 51 participants last post by  150EH 
#1 · (Edited)
1 The idea

A long time ago I read about large plywood tanks. Fools, I thought... wood and water? A couple of years back I started wondering about it some more, comparing a plywood tank to a commercial glass tank. The economics didn't add up, so I bought a 55gal tank and forgot about plywood. More recently, the idea surfaced again. Now I am less worried about the economic side of it, but thrilled with the idea of a large home-built tank, with lots of invisible plumbing, water change system, and a generous depth, to fit exactly into a place where a 100gal tank sits now.

I am no professional wood worker, and before attempting something like that, I wanted to first get some on-hand experience to reduce the risk of a major screw-up, like flooding my house with several hundred gallons of water. So I started looking at my neglected 55gal tank with it's lack of depth and figured the nice big front and back glass might work well in a larger plywood construction.



Sitting in the garage, it wouldn't have to be perfect, and if it catastrophically failed, the worst that could happen is a lot of water draining out of my garage door.

In this journal I am going to show pictures of what I did step by step and the results of it. I don't want to challenge your patience, and had no clear idea if it would work (still don't) and how long it was going to take to finish. So by now I am a few steps ahead, and some of the epoxy is already drying.

But this is how it started...

1 The idea (this post)
2 Planning and preparation (next post)
3 Smashing a perfectly fine tank and building a foundation
4 Plywood, screws, glue and sand paper
5 Epoxy
6 Glass & Silicone
7 Plumbing & Filtration
8 Lighting
9 Moving it into place
10 Wet Day
11 Substrate
12 Conclusion
13 Top Lessons learned
 
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1
#2 ·
2 Planning and Preparation

The more careful planning is done upfront, the smoother everything will work in the end. Since I was not in a rush, I took several months to think about it, read other successful and unsuccessful projects on the web, measure things here and there, evaluate the space and create a very detailed plan with a computer. Here is the schematic of the setup, created in Visio:



Along with that, I created a plywood cut plan, which helped to minimize waste. Going back and forth between the schematic and the cut plan, I optimized the size for my future tank construction. Originally I wanted to keep the length of the tank to 48" to take advantage of the plywood sheet size, but that would have meant to cut the glass panels, and I figured some additional length to build filter compartments into the tank itself would be cool too. Basically I ended up with two tanks, each of them LxWxH 60x22x24", resulting in two stacked 135gal tanks.



My collection of woodworking tools is fairly basic... We will need a drill or two with a selection of drill bits, a circular saw, some clamps, measuring tape, and a square. I also own a table saw which isn't necessary, but comes in handy sometimes. I often jump on super cheap deals at Harbor Freight, and my collection now includes cheapo jig saw, finishing sander, and grinder/cutoff wheel. And a rotary tool for different purposes.



Financially, I don't think this will save a lot of money over buying an off the shelf glass tank, especially when counting the hours that go into the project. I don't count them, because this is a fun/spare time project for me. Plywood gives us flexibility with regards to the size and plumbing which gives it an advantage over store bought tanks. And if it holds without leaking, there will be a large confidence boost... hey, I made this! Of course that can go the other way too.



One thing to consider... if not in a hurry, expenses come gradually, which is easier to swallow than one big lump sum. I bought the Epoxy months ago, the plywood over time, usually it didn't cost more than $60 a pop. Having the glass was a large saving for me. 2x4's and wood glue are very cheap items, and over several months I looked for deals that helped me to keep all of this fairly inexpensive.
 
#5 ·
3 Smashing a perfectly fine tank and building a foundation



Once the 55gal tank was emptied, the question became how to separate the glass panels. A razor blade and a lot of tooth floss are a good starting point. The first seam is the hardest, once it is unglued all the other seams are comparatively easy to separate.



After half an hour with the razor blade, my patience ran out and I grabbed a hammer. Since I didn't need the side panels, smashing them carefully sped up the process immensely. The bottom panel of this 55gal tank was tempered, and to compare some I took the hammer to it as well. I found that tempered glass is much, much harder to shatter, and once it broke, it broke into hundreds of little pieces as expected. They are still very sharp... ouch.



As a side note, it might seem a bit weird to cut up a nice 55gal tank, until you realize how expensive glass panels can be if you buy one or two. With applied economies of scale, buying a complete 55gal tank is cheaper than buying the separate glass panels!



The floor in my garage is angled towards the street, and curved towards the center. Not a good base for a large tank. Therefore, I decided to build a concrete base. Soon I realized that this wasn't as easy as it seems, but after a couple of layers it was all built up fairly straight and level.



I am planning to add another layer of fresh thinset just when lowering the plywood construction onto the base, to make sure it is well supported and level.



To keep energy costs reasonable, I removed the drywall and filled the space with insulation. This should help to keep the tank temperatures cozy during icy winter nights. The plywood should insulate a little bit, and I will cut a fitting piece of styrofoam insulation to cover the front glass. As you can see, I also painted the garage floor with epoxy paint. Very easy to do, and makes a big difference in appearance.

 
#6 ·
plywood tanks are awesome! my friend has a 500 gallon plywood tank and the thing is huge!

one concern that comes up is the glass, do you think the 55 gallon glass panels are enough to hold the extra weight?......also if ur 55 gallon was a standard 55 shouldn't all the panels be tempered?

w/ those dimensions i get a minimum thickness of 0.31" @ safety factor 2 for non-tempered and .10" @ safety factor 2 for tempered glass.
 
#8 ·
plywood tanks are awesome! my friend has a 500 gallon plywood tank and the thing is huge!
That's one nice thing about plywood tanks, they can be easily scaled up. Plus you can make them to fit perfectly into any nook/cranny.

one concern that comes up is the glass, do you think the 55 gallon glass panels are enough to hold the extra weight?......also if ur 55 gallon was a standard 55 shouldn't all the panels be tempered?

w/ those dimensions i get a minimum thickness of 0.31" @ safety factor 2 for non-tempered and .10" @ safety factor 2 for tempered glass.
It's about 50/50, some 55gal tanks come with tempered sides, others (like mine) have only the bottom panel tempered.

To be honest, I haven't given much thought to whether the panels are thick enough. I figure additional depth of the tank does not add a lot of weight (and I am probably wrong about that), and the height and length of the glass panel won't change. Instead of small silicone seams, the whole panel will rest against a (hopefully square) plywood frame, which IMO should not add much or any stress.

I forgot the size of my piece of glass, but it was atleast $200 for the hunk with polished edges. Not cheap.

Keep the pics a comming :)
Your glass was a bit larger and probably thicker. One nice option is to use low iron (Starphire etc) glass for improved clarity. Not cheap though.

I have some more pictures lined up, stay tuned. :smile:
 
#10 ·
I am building a plywood glass tank right now its 80% done. I purchased 1/2 starfire glass for my veiwing window dimensions of tank are 97 1/2" by 24" by 24" 240 gallons I believe. The glass is 95" by 23 1/2" the glass is 95" by 23 1/2" the glass cost me $320.00 with beveled polished edges. I used fiberglass resign and cloth to seal it then I painted it with sweetwater epoxy paint from aquatic eco systems one gallon came to $110.00 that including shipping. If you would like to see pics so u can get some ideas just let me know. gotta love DIY
 
#12 ·
Sweet, I'd love to see pictures, why don't you start a thread for your project? I am sure there are many that would like to see that. Thanks for sharing your materials and prices, I'll get into these details very soon.

Did you use the West System epoxy? Why do you use Sweetwater epoxy paint, as an additional seal for the epoxy? How did you deal with the fumes?

Very cool. An awesome project indeed :)
Thanks for your kind words! :smile: I'll agree with you if it holds water...
 
#13 ·
4 Plywood, screws, glue and sand paper

To build the box, I used 8x4ft 3/4" plywood panels. When it comes to plywood, there are many choices, from very cheap (~$25) to better quality (~40) to really expensive hardwood (~$55). The main drawback of the cheap boards is that they come with lots of imperfections that might need considerable time to fix, and can even negatively impact their strength. This usually surfaces when you cut the boards and spot gaps.



For front, bottom, and sides I went for the middle-of-the-road, better quality plywood from a lumber place, where they also helped me with some of the long cuts. There is nothing that can't be cut just as well with a circular saw at home, but it is definitely easier to have this done with a large industrial saw, especially if they only charge like 50 cents a cut.



For the back, I was going to join two sheets, but then decided to use a different approach. I bought four very cheap, thinner boards (0.45") and doubled them up, so the join runs vertically on the back and horizontally in the front. Gluing the 60x60 board together was quite an interesting experience. I used a door as the base, since my garage floor isn't straight. Then I collected all clamps, buckets, concrete bags, and water bottles to press it all together.



It turned out alright, but like I mentioned, with cheaper plywood you get a lot of imperfections, and it took a couple of hours with wood filler and sander to get it all nice and smooth.



I bought 2" drywall screws at the local hardware store, and I used a couple of 18oz bottles of Gorilla glue to keep it all together. One very inexpensive way to increase the structural strength and assure the weight of the water does not pop the glue seams is to add triangular pieces of wood, ripped 45 degrees from 2x2's. This is where the table saw comes in handy... I glued these strips to all inside corners.



I opted for an integrated filter (and stuff) compartment. This makes applying the epoxy much harder, but I went for it anyway.



Main reasons: I don't want to use a canister or HOB or any such external filter. With the tank sitting in a garage that is not insulated, I think external filters would aggravate temperature swings, I would need more wattage in Winter, and the tank would heat up faster in Summer. Plus, with the tank design as it is, I wouldn't really know where to place it. Internal filters in the tank look ugly, and are messy to clean. Thanks to plywood I just added some length to the tank for 3 compartments (see schematic in second post): One for the pump (as well as heater, overflow to lower tank, and fertilizer reservoirs), a second center compartment for filter sponges, and a third "dry" compartment for some equipment, micro fertilizer, maybe maintenance supplies.



Braceless tanks make maintenance much more fun, and no light is reflected by dirty glass braces. For the top tank, I used a steel angle to add the necessary stiffness to the plywood.



The bottom tank is mainly planned as a fancy water reservoir at this point. It will get a shorter metal angle, combined with a threaded rod that goes from the front to the back panel to prevent any bowing.

One of my main concerns about possible weak points is that the top tank is mainly floating in air. When full of water, this is going to be a lot of weight supported by the sides panels. To prevent the bottom from bowing and ripping the front glass out of it's silicone bed, I added a 2x4 in front, 2x6 in the center, and a 2x2 in the back (where it connects to the back panel). Hope it will hold! I might add some more support from the outside.



Here is another shot adding the 45deg strips:



For easier access and handling, I am keeping both tanks and the back panel separate while applying epoxy. When done, I will screw the back panel to the tanks and apply epoxy to all the joins. The 60x60 double plywood back panel is very heavy, and when combined with the tanks I need another person to move it around.



At this stage I -cough- started to sand everything really smooth. Sanding sponges are my favorite tool, even though I used a finishing sander for some of the larger areas. Well, almost ready for some epoxy!
 
#14 ·
looks verry nice, I know i need to start a thread and im working on it. Its going to be a diy thread. The thing is im building some acrylic tanks some opent top frameless glass tanks and the monster 240 gallon plywood glass tank. When these projects are all done i will have an all in one thread.

To answer your questions the reason I used the sweetwater epoxy paint is because when I started this project I diddnt know about west systems epoxy so I used fiberglass resign and cloth that I bought by the gallon at the auto parts store. It worked great but then I was worried about the resign poisning my plants and fish so I put 3 nice thick coats of the sweetwater epoxy over the fiberglass resign so all together the fiberglass resign is about 6 mm thick with another 4 mm of epoxy paint over that, guarenteed not to leak and verry strong
when you apply your epoxy if you buy it by the gallon I suggest only mixing up 1/3 at a time so its not setting up on you before you use it up it does stink so I opened the garage door turned on the exaust fan and used 3 other fans to blow the fumes away as I painted and I also suggest buying cheap brushes and dont try reusing them and wear rubber gloves.
 
#16 ·
looks verry nice, I know i need to start a thread and im working on it. Its going to be a diy thread. The thing is im building some acrylic tanks some opent top frameless glass tanks and the monster 240 gallon plywood glass tank. When these projects are all done i will have an all in one thread.
Sounds like your are a busy person! Takes me months just to get one little project started.

To answer your questions the reason I used the sweetwater epoxy paint is because when I started this project I diddnt know about west systems epoxy so I used fiberglass resign and cloth that I bought by the gallon at the auto parts store. It worked great but then I was worried about the resign poisning my plants and fish so I put 3 nice thick coats of the sweetwater epoxy over the fiberglass resign so all together the fiberglass resign is about 6 mm thick with another 4 mm of epoxy paint over that, guarenteed not to leak and verry strong
I never thought of checking out Auto Parts store... So is fiberglass resin and epoxy two different things? Is fiberglass resin aka polyester resin? May I ask how much a gallon of that stuff costs you?

when you apply your epoxy if you buy it by the gallon I suggest only mixing up 1/3 at a time so its not setting up on you before you use it up it does stink so I opened the garage door turned on the exaust fan and used 3 other fans to blow the fumes away as I painted and I also suggest buying cheap brushes and dont try reusing them and wear rubber gloves.
I am in the final stages of applying epoxy, I went a different route (not West Systems) and we'll see how that pins out. I am going to describe the details in a separate post with some more pics. :smile:
 
#22 ·
I didn't get the fiberglass stuff, I went with epoxy which is hopefully waterproof for extended periods.

Seems like some go with the West System and then in addition to that paint it with Sweetwater Epoxy paint, which seems like expensive overkill. But it makes sense to paint the fiberglass resin.

I'll post some of my epoxy adventures over the weekend, just need to sit down with Mr Photoshop for a little while. :icon_roll
 
#25 · (Edited)
5 Epoxy!

Honestly, I was a bit scared of epoxy. Fast setting time, almost explosive heat development, and brain cell damaging smell was what I had read. None of that was quite the case. After a while I figured out that it is just some glorified glue. I spent some time to research which epoxy would be the best for my situation, and ended up with Coat-It made by Goop.



Compared to the more obvious choice (West Systems) this epoxy comes in at half the cost, has a dark coloration, and requires only 1 to 2 coats. It has a very syrupy consistency, wetting out fiberglass mats would be almost impossible. It also makes painting vertical surfaces quite easy. The smell is very benign, I suffered no immediate brain damages besides a very light headache in my not so aerated garage. After 12 hours Coat-It starts to get less tacky, and after 2 or 3 days it feels dry.



Important things with epoxy - take the right proportions, and mix well. I got an 8lb kit of Coat-It which covers around 80sqft (about the size of my project). 7lb resin and 1lb hardener, so it needs to be mixed 7:1, which was simple enough with a little scale that otherwise weights fertilizer powders. One of the things to avoid with epoxy is to get it on your skin... can you say itch & burn? I wore two pairs of gloves, thin latex underneath some heavy duty ones. The latex ones help to get the thicker ones off without touching any epoxy.



The dark coloration makes it easier to see where the coat is too thin. I did two layers in most places. To apply it, a fairly stiff bristled brush that didn't shed hairs worked best for me. Neither freezing the brushes nor keeping them submerged in paint thinner kept the epoxy from hardening, so I just threw them out after each painting session.



Like I mentioned earlier, kept both tanks and the back separate to make painting easier. With the filter compartments, it would have been difficult to paint with the back panel attached.



After silicone-ing the front glass panels, I will screw/glue the back to the rest of the construction and paint just where the corners meet. Already drilled a hole into the garage wall for the overflow. Time to think about how to lift the whole thing up onto its concrete base. I'd like to suspend it in the air somehow, while adding some thinset, and then lowering it down into the fresh mortar to provide the most level surface.

 
#27 ·
lookin good, can I ask where you purchased the goop coat it ive never heard of it and if its halph the cost I would like to get some? Where you able to buy it locally at a home depot or lowes or did you have to order it online? In my case I ordered from aquatic eco systems that charged me a $30.00 hazmat fee on top of the regular shipping fee.

I just have one suggestion you might want to mix some more epoxy up after you screw the back on. I tipped my tank so it was kind of like balancing on the corner shim each side so it stayes then pour a nice bead of epoxy all the way down where the back and bottom meet. when I did it the epoxy leveled it self and made a verry strong seam. its just a suggestion I did mine like this on every seam. Just a little easy insurance that it wont leak. good luck and nice job
 
#29 ·
lookin good, can I ask where you purchased the goop coat it ive never heard of it and if its halph the cost I would like to get some? Where you able to buy it locally at a home depot or lowes or did you have to order it online? In my case I ordered from aquatic eco systems that charged me a $30.00 hazmat fee on top of the regular shipping fee.
Here is where I discovered Coat-It first. They also have some more information about it. Here is another sheet with some information. I bought it from this place, cheapest incl shipping for me.

Aquatic Eco is nice, but for a budget conscious DIY'er like me a bit too rich. Their shipping charges are not competitive for small orders.

I just have one suggestion you might want to mix some more epoxy up after you screw the back on. I tipped my tank so it was kind of like balancing on the corner shim each side so it stayes then pour a nice bead of epoxy all the way down where the back and bottom meet. when I did it the epoxy leveled it self and made a verry strong seam. its just a suggestion I did mine like this on every seam. Just a little easy insurance that it wont leak. good luck and nice job
Most of the seams in this construction are reinforced with triangular 2x2s, which should add a lot of strength. But for those that are not, I will do that... if I have enough Epoxy left over.
 
#30 ·
Good point there... Doing several layers of glassfiber mats and epoxy will create a much stronger/better protection against falling rocks. Heavy, sharp edged rocks would probably puncture the epoxy layer that I painted over the relatively soft plywood. Knowing that, I will not use large rocks in this tank, and be careful when working with pokey objects inside the tank.

I can't say how thick the epoxy layer exactly is. I hope thick enough. :smile:
 
#35 ·
Basically just one layer of epoxy. I painted a second time in areas that seemed to light. This stuff sticks really well to anything, including itself, so I skipped the sanding-in-between.

Well I've been waiting for this project to take off. :proud: (I remember reading/posting in another thread discussing the idea months ago)

Looks like you're off to a great start and I'll be watching this one.

The scary part for me is that I have two ancient thick glassed 55g's sitting in a corner of a four bay garage that are beginning to call out to me when I walk past them....:eek5:lol
Yeah, only took me like two years to get this started. :icon_roll If this works out, I have a larger project already lined up... now that's scary.

Awesome. A Jedi Master of DIY.

-O
Thanks O, hehe, plenty of satisfaction if I can make something and it works afterwards. I don't save money, but I always learn something in the process (even if it is "never do THAT again").

Sweeeeeet. Glad to see you are still pursuing this....:thumbsup: See what happens after ya drill that first hole through a wall......:biggrin:
Yep, that semi-automated waterchange setup seems so innocent now...
 
#32 ·
Well I've been waiting for this project to take off. :proud: (I remember reading/posting in another thread discussing the idea months ago)

Looks like you're off to a great start and I'll be watching this one.

The scary part for me is that I have two ancient thick glassed 55g's sitting in a corner of a four bay garage that are beginning to call out to me when I walk past them....:eek5:lol
 
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