# large PVC trim board tanks -- construction diary



## carbonetc (Oct 13, 2008)

So, a few years ago I wanted to build some big display tanks for frogs. Now I'm moving and I need to sell them so I'm finally getting around to putting together a build log. I haven't noticed if anyone else has built tanks like these since I built mine, but I had never seen these materials used before -- not on this forum anyway.

My goal was to avoid the pitfalls of glass and wood. Glass is heavy and breakable. And it's wasteful to build a box out of glass when three of those back walls are just going to be covered by a background anyway. Wood is light and flexible, but it rots. It takes a lot of money and work to waterproof it using marine epoxy or pond liners, and even then rot may eventually happen.

I didn't want to bother with any of this, so I found a material that gives me the best of both worlds.


*PVC Panels*

Cellular PVC is, essentially, plastic wood. You can find boards and panels of it in home improvement stores and lumber companies sold as a fully waterproof replacement for exterior wood trim. Common brand names are Azek, Versatex, TufBoard, Kleer, etc. "Cellular" refers to its internal structure. This isn't solid PVC like the plumbing in your home. At its core it's spongy/foamy, making it lighter and more flexible than solid PVC. The size of the internal cells will vary depending on the quality of the boards you buy -- in high-quality board you can barely see them. Everything you can do with wood (drilling, painting, sanding) you can do with cellular PVC, and everything you can do with PVC (chemically welding, creating watertight structures) you can do with cellular PVC. It's wonderful stuff. 

Here's my original diagram while in the planning stages:










I went down two blind alleys while I was figuring out how I was going to design this thing. My first mistaken assumption was that I was going to have to use store-bought boards to keep my costs down. I figured ordering custom cut panels would be well out of my price range. My most advanced woodworking tool is a tiny table saw, but even if I had the necessary tools to cut large panels, panels aren't typically sold in stores -- only boards. I would have had to order the panels and pay freight fees to have them shipped. No good.

So, my plan was to buy the widest boards I could find (around 15") and weld them together edge to edge with PVC cement to make panels. Since a welded PVC joint is actually stronger than the PVC around it I didn't have any structural concerns. But it was going to be a huge pain in the butt. After doing a bunch of math to figure out which size tank would require me to buy the fewest boards, I finally did the smart thing and got some estimates from nearby lumber companies for custom cut PVC. The response was a total surprise. Not only would cut panels cost me about as much as my crazy board-welding scheme, but many different thicknesses of panel were available. In stores you can only find 3/4" thick board. Had I built the whole tank out of this it probably would have been extremely bulky and heavier than I wanted. I ended up buying 5/8" panel for the bottom and 3/8" panel for the sides so the tank would be strong where it needs to be, yet lightweight where it doesn't. For pieces like the front vents and top bar I used store-bought 3/4" board for the extra structural stability. I could cut this stuff myself anyway.










My second mistake was choosing cleverness over efficiency in putting the pieces together. Since you can weld PVC, I figured I would assemble it and waterproof it all at once by welding it together. Smart, right? No. Stupid. It was very difficult to get large pieces pressed together properly even with slower-setting Weld-On (a cement I spent way too much on). I gave up almost immediately and switched to screws. You never know when you've botched a PVC joint until it breaks, and it was worth it to me to avoid all that uncertainty and put it together the old-fashioned way.










The result, once assembled, is a ~100 gallon tank that I can lift off the ground by myself and that could easily survive being dropped or even thrown. Try doing that with glass.


*Tank Size*

The final dimensions of this tank are 30" wide by 32" tall by 24" deep. I had a few reasons for going with a 30" wide tank rather than an even three feet. The first was my available space; I don't have nine feet of clearance where my tanks are going to live. But there are other good reasons as well. Most boards, sliding door tracks, and other accessories come in eight foot lengths: 96 inches. Notice how nicely divisible that is by 30. I get material for all three tanks and have a little left over for error. If I had gone with 36" I would have found myself buying two of everything and wasting almost all of it. Further, a length of steel mesh (for the vent) will probably be 36" wide. In order for this to fit my tank I need to hope that it's cut just right and that the edges haven't frayed any. Again, 30" lets me buy a single piece with extra room for error. I thought that this width might present me with lighting problems, but it turns out there are all sorts of 30" T5 HO fixtures out there. They do use 24" bulbs, but since I have a couple inches worth of background on either side of the tank I don't need to light the edges anyway.

The depth of the tank was just a nice round number, but I also made sure that I would have plenty of clearance moving this thing through hallways and doorways -- especially with a drain hanging off the back. 24" has been a pretty safe depth so far.

There's no particular reason for the height I chose. I just wanted to get the tank volume up to around 100 gallons.


*Drainage*

Putting holes in PVC couldn't be easier. My drain holes require a 9/16" spade bit and 1.5 seconds. Installing the drain couldn't be easier either. When welded, not only is it as waterproof as your home plumbing, the joint is strong enough that I can pick up a whole tank by its drain. Everything needed for this drain can be found in stores. 










I used 1/2" PVC pipe, a 1/2" elbow (slip connection on one end, threaded connection on the other -- this is important), and a screw-in barb made for connecting flexible plastic tubing. You can also buy a threaded plug to close up the drain for when you're moving a tank around. 

This is how everything cements together. Shown is the tank wall on the right, the pipe extending into it, and the elbow piece on the left. The purple is the PVC cement connection.










I installed the drain at the middle of the back wall of the tanks, but realized later it would have made more sense in the corner. If you want to empty the tank by tipping it, the corner would make it so much easier.

In this hobby we're used to using silicone on everything, but silicone won't stick to PVC well enough to seal the bottom and prevent it from leaking. I used my Weld-On to fill the cracks at the base of the tank where there would be perpetual standing water.


*Doors*

I had my sliding doors cut professionally out of 1/4" plate glass. It can be difficult to find E-track online for thinner panes of glass. Most of it is the tan-colored 3/8" track, which I did use on the first tank I built. For my display tanks I finally found some gray-colored 1/4" track. I wanted the tighter fit to keep in humidity and to keep baby thumbnail frogs from escaping.










Before you silicone E-track to something it's crucial that you rough up the back of it. I dragged a dremel sanding bit haphazardly across the whole surface until it was gouged up pretty good. The silicone needs some tooth to really stay attached.


*Venting*

I went with your typical European tank design: a thin slit below and behind the doors lets the air in.



















The front below the doors is a screened vent. I used some very tight stainless steel mesh that I found online (not easy). 










To cut it I would tape a rectangle roughly the size of the piece I wanted and then draw precise cutting lines on the tape. The tape keeps the edges of the mesh from fraying while you cut it and handle it. 










I secured the front edge of the mesh by siliconing it between the E-track and the PVC. On smooth PVC this wouldn't have worked, but I was using the lower quality trim for the thin front piece, and the edges of this are very rough. For the back edge I found some L-shaped plastic strips online (at least as hard to find as the mesh). I roughed up the insides of them for siliconing as I did with the E-track.

The vents are the part of the build I regret most because I simply didn't need them. I spent all this time and money designing them and I ended up plugging them up with foam because they allowed the tanks to get too dry. They also slowly ruined the Ikea table the tanks are resting on because leaves hanging toward the front of the tank will drip after the misters go off and the water falls right through the mesh. That's a type of leak I just hadn't planned for. Something much less elaborate to bring air into the tank would have done just fine. The only good thing about having built these is that they're a nice sturdy handle for carrying the tanks around. Oh well. They look neat.


*Top*

The top is the cheapest part of the build. I never was very satisfied with how I did the tops. They're panes of the typical 3/16" glass you can have cut for you at Lowes or Home Depot. It's nice and cheap so you aren't too disappointed when you ruin one while drilling a hole for the misting nozzle. I edged them with electrical tape to keep them from cutting me when I move them around.










The glass is supported in the corners by these little pieces of PVC trim -- shims, I guess? I cut a bunch of these shims for use all over the tank. The reason is I had no good way to screw two 3/8" thick pieces of trim together. They're too thin to accept screws in the edges. So instead I screw each piece of trim into the shim which indirectly screws them together. I made sure the shims at the top were level so they could do double-duty as glass top supports.

This wasn't ideal. There was a lot of variation between tanks and glass tops. Sometimes the glass would fit snugly and sometimes there'd be gaps. I found out the hard way how big some of my gaps were; I found a few vanzolinis on my floor before I figured out how they were escaping. If had done it all over again I would have put thin strips of trim (instead of shims) all around the top of the tanks. It would have added a little weight, but it would have been worth it. No gaps, no bowing of glass between corners, and the tanks would be as sturdy on top as they are on the bottom (they're a bit wobbly when you carry them, and I wonder if this may cause a foam background to separate one day).


That about covers the construction itself. I needed three tanks, but I ended up building six. I figured I'd sell a few to recover some of my costs. Once you get the hang of it it doesn't take long to build them assembly-line style.










I had to be just as inventive with the backgrounds as I did with the tanks. I'll devote a whole other post to the tank interiors soon.


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## Tykie (Mar 22, 2015)

I would be intereted in buying a few of these from you ??
PM me with a price ? 

Tykie


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## daisymaisy01 (May 19, 2015)

Thanks for posting, this is a great idea. You've done a great job!


Sent from my iPhone using Tapatalk


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## Judy S (Aug 29, 2010)

looking forward to how you worked with the background....


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## a hill (Aug 4, 2007)

I'm really liking the work with pvc panels people are doing. I think my next big tank will be mostly pvc. Besides fumes from the cement, I love it. Bulkheads on acrylic is a pain and super expensive


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## jpstod (Sep 8, 2005)

Love the Look so far...I am interested since I am looking into opening a Nature Center...Need Easily constructing Matterials as I most likely will be doing most of the work solo to keep costs down.


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## Broseph (Dec 5, 2011)

This seems really cool. I love the fact that you can chemically weld plumbing components and PVC false bottom stilts. You could attach all sorts of PVC skeleton pieces for making cork branches and plantable ledges, duct work for fans... The possibilities are endless.

How does the price compare to glass? Glass work is easy enough, but if this method is financially comparable... wow.


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## carbonetc (Oct 13, 2008)

*Background*

Silicone won't stick to PVC, but expanding foam seems to stick just fine. Many many cans of Handi-Foam went into these three backgrounds. I prefer Handi-Foam to Great Stuff because it's less squishy and because it's dark colored, so if it's ever exposed you don't get light spots everywhere.










Notice the silicone on the PVC walls. This is where I learned it was useless. It's typical to put down some silicone before you start foaming a glass tank, but it came right off. I abandoned it.

When it came time to cover the background I had to get inventive. The method where you push peat into a layer of silicone wasn't going to work out. Coverage alone for these three big tanks would have taken weeks, but I also would have had to rough up every inch of the Handi-Foam to get it to stick well. My first experiment just peeled off. I needed something quicker and easier.

So I researched what I could just spread on the surface and be done with it. I read that some people were using Titebond III wood glue. This is food-safe ("approved for indirect contact with food") for humans when dry, so the thinking was that it would also be safe for frogs. People had used it with success so I went for it.

To make the mixture, I poured the following into a bucket I didn't plan on using ever again: the glue, water, peat moss, coco peat. What you want, ultimately, is something the consistency of pudding. It will look like gray mush. I don't remember the proportions I used but it doesn't seem to need to be exact. Use water in small amounts to loosen up the mixture and make it more manageable, or to rehydrate if it's been drying out while you work.

Wearing disposable gloves I smushed a thin layer of the stuff all over the Handi-Foam. If you do only this you'll end up with a surface that looks like wet or damp dirt. To add some texture I sprinkled a little of the dry peat mixture over it whenever I finished a section. It makes it a little more natural, I think.

This method works perfectly except for one thing. This stuff dries hard. Very hard. If you're used to being able to just pin plants to your backgrounds you're going to have some difficulty. It takes some effort to poke pins through this stuff, but it can be done. It'll look like dirt, but it won't feel like it. You could knock on it and hurt your knuckles.

I only wanted this stuff to cover the foam background and leave the PVC edges exposed. While working I'd wipe up any glue that ended up on the PVC. Once it dried it was easy enough to use the edge of a credit card to scrape the residue away fully.


*Floor*

I cut up a narrow PVC pipe into many small pieces and cemented them to the bottom to act as stilts for a sheet of eggcrate light diffusor. I laid landscape fabric over top of that so as little material as possible would fall into the empty bottom. I did this while I was working on the Handi-Foam background, so I just put a bead of foam along the edge of the fabric to secure it in place forever.

I also tried building some ponds. There are areas where I cut a section out of the eggcrate and built a cup out of Handi-Foam. I let the cups get tall enough that they'd rise above the eventual substrate so there'd be no erosion into the water. I covered these the same way I covered the background.

This was nearly successful. They look great, but I found that water will wick up out of the ponds. They need to be refilled every week or two. I don't really know how to get around this. You'd need some sort of barrier of non-absorbent material between the pond walls and the surrounding environment (the above-water walls, the substrate, etc). I don't suspect that they're leaking into the bottom since the glue is waterproof, but I can't know for certain.

I finished off the bottom by covering the fabric with an inch or two of ABG mix.


I apologize that I don't have more photos of this process. I had a hard drive failure soon after I finished up the tanks and I lost most of my progress photos. If I ever find them I'll post them. Except for the wood glue mixture it was pretty standard. 

The next post will be recent photos of the tanks, completed and populated and filled in.


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## carbonetc (Oct 13, 2008)

Broseph said:


> This seems really cool. I love the fact that you can chemically weld plumbing components and PVC false bottom stilts. You could attach all sorts of PVC skeleton pieces for making cork branches and plantable ledges, duct work for fans... The possibilities are endless.
> 
> How does the price compare to glass? Glass work is easy enough, but if this method is financially comparable... wow.


Yup. I have no idea why people still use glass. Glass is for fish.

At Home Depot I found a PVC utility door. I would have installed that in the back if I'd had a pump that needed servicing.

The PVC for six enclosures, already cut to size, cost around $750. I probably spent another $100 on the smaller pieces I bought at Home Depot and cut myself, but I wouldn't have needed most of those pieces if I had skipped the vents.

So, divide that by six and compare it to the glass needed for a 100 gallon custom tank. There were savings for buying in bulk, however. If I were to design a single tank like this the PVC would cost $250-300 from my supplier. You buy whole sheets of PVC, so you're stuck buying a bunch of extra.


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## zerelli (Sep 14, 2009)

I love the look and the idea of the material being durable, but wow what a price! I might have just seen the high end cost but at $125US for a 4x8 sheet, I think I will stick with wood and glass. Of course, I get great deals on glass locally so I am in a different situation I guess.


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## Mossy (May 20, 2015)

The possibilities with pvc are endless. Very cool idea. Can't wait to see it all finished.


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## carbonetc (Oct 13, 2008)

I'll put the smaller versions of the recent vivarium images below so the downloads aren't massive. Here's a link to the full album of images so you can browse them and view them at full size: pvc vivarium build










This is tank #1, and it's my favorite. It houses oyapock tincs. There's a completely obscured pond in the front left corner, and there's a mini-pond partway up the wall on the right, but it doesn't hold water well (wicking problem). The bromeliads are growing off of cypress knees standing in the middle of the tank. There's a cypress wood shelf at the top left, though you wouldn't know it at this point. The marcgravia has made layers and layers of itself high up in the back and is now just expanding outside of the enclosure through the gaps.










Tank #2 was built for vanzolinis. I used to have more bromeliads lower down but the ones up top got so big that the lower portion of the tank is hard to keep lit. Now I only have two males (father and son) so I've been less concerned about making breeding areas available. This is the tank shown in progress earlier with the two branches. It has some wood piled at the bottom for hiding places but much of it is decomposing now.










This tank is uninhabited and I've pretty much let it go and use it as a place to temporarily hold nepenthes I've no more room for. Two angel wing begonia species have covered everything. I left the doors on in this photo so you can see how they work. The front panes on each tank have gray weather stripping on the back to help keep in humidity and to make it harder for fruit flies to just waltz out of there.


These tanks are all for sale at a huge discount and I'll be listing them in the classifieds shortly. Obviously it's going to be pick-up only.


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## rigel10 (Jun 1, 2012)

Very nice! Maybe you said it over and I missed: how did you sealed the corners to make them waterproof?


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## chillplants (Jul 14, 2008)

I had an idea for using expanding foam as a background and giving it something to really hold on to. My thought is to use eggcrate for the foam to hold on to. Place a couple metal washers in between the eggcrate and the PVC and screw the eggcrate to the PVC. The spray foam would work itself into the cracks and in between the 2 layers thereby anchoring itself in place. Assuming this works, you wouldn't have to worry about the foam separating from the walls and falling off.


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## carbonetc (Oct 13, 2008)

rigel10 said:


> Very nice! Maybe you said it over and I missed: how did you sealed the corners to make them waterproof?


I used Weld-On. It's a type of PVC cement, but it's thick and takes 30 minutes to cure (vs. seconds for typical PVC cement). It would have been ideal to get it between pieces but that wasn't feasible. So I used it to cover any joints after construction that would be exposed to standing water.


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## a hill (Aug 4, 2007)

These tanks came out great! They look so clean and shiny. 

Locally it seems there is a minimum order of $100 at the distributor for the material and that is for ten 4x8 boards. Having them cut down would be approximately $20-$50 depending on specific cuts. 

Does that sound about right to you? 

There is also a new pvc board structure that is supposed to be 10x stronger per thickness of the normal boards. Price is higher, but when I talked to someone at the manufacturers office they said I would likely be able to use 2mm thickness for large tanks! Talk about lightweight. (I'm unsure of price, I was told it's much higher than regular board.)

This thread is of great value to the hobby I think, or at least for me. Thanks for posting and I hope they are still doing well. 

-Andrew


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## TheCoop (Oct 24, 2012)

They look great, my design and material were the exact same when i build Bearded Dragon enclosures in the late 90's, mine were 36"x20"x20"..


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