HELP! DIY plywood tank questions!!

[CatmanJuice]

This is my first Plywood tank build, I've already built the frame for the tank, and had a couple questions that I can't seem to find consistent answers for: (and need to figure out before I make any mistakes)

1. Which is the best? Pond Coat, Pond Shield, liquid rubber, etc. for use with a glass front? I have heard that people have had problems getting these to stick to glass, is this true/ what works best?

2. Glass thickness? The inside tank dimensions are 84"x36"x26" (LxWxH) and the tank will have a 84"x24h" front viewing pane. I have heard everywhere from 3/8" to 3/4" glass thickness.
Would 1/2" tempered work with 3 center braces and top and bottom braces?

Please any advice! I've looked through threads here and seem to get a lot of mixed opinions. Just wanting to make the right steps before I can go any further with the build.

Thanks!
Juice

 

[CJH]

Which is the best? Pond Coat, Pond Shield, liquid rubber, etc. for use with a glass front? I have heard that people have had problems getting these to stick to glass, is this true/ what works best?

Pond Coat and Liquid Rubber are basically the same thing. One might be better suited for spraying and one might be better suited for troweling (or something like that) but they are very similar otherwise.

But to your question, there is no perfect sealant for plywood tanks. If there was there wouldn't be conflicting information. Each sealant type comes with its own set of tradeoffs.

I don't believe there have been any glass adhesion issues with Pond Shield but there have been some issues with cracking. It is rumored that Pond Shield isn't flexible enough for anything other than the most sturdily built plywood tanks but I have no direct experience with this.

As far as adhesion issues with glass and Pond Coat, if you do an extensive search of this forum you'll find that two different distributors have recommended very similar approaches for adhering glass to plywood tanks that will be sealed with PC.

One is to attach the glass with butyl rubber caulking directly to the bare wood and then to seal with PC up to and onto the caulking bead.

The other made the same recommendation but suggested fast cure polyurethane caulk rather than butyl rubber caulk.

So unless you've read about one of those methods failing I wouldn't worry about it a whole lot.

If it were me I'd take it a step further and seal that area of bare wood with epoxy first but it's probably not necessary.

Other than Drylok, there are five basic types of products that can be used to seal plywood tanks. They are:

1) Polyester and Viny Ester Resins.

2) Epoxy resins.

3) Solvent based epoxy paints.

4) Polyurea.

5) Elastomeric emulsions (Pond Coat, Ames Blue Max, etc.)

I lump polyester and vinyl ester together since they are similar to work with. I separated epoxy resin and epoxy paint since they are somewhat different to work with.

 

[CatmanJuice]

Thanks CJH,

I have seen the information about using butyl rubber and that will probably be my caulk of choice for attaching the glass to the wood. I will probably not use Pond Shield since it has the possibility of cracking, I am looking for a sealant that will be more flexible once cured (I think I have gathered that Pond Coat will provide this). I think my only concern with the Pond Coat then will be its ability to hold over all three surfaces (butyl rubber, plywood, and glass) where the three meet, and staying water tight in those connections around the glass.

And any advice on the glass? 1/2inch tempered sound ok?

Thanks all,
Juice

 

[CJH]

Thanks CJH,

I have seen the information about using butyl rubber and that will probably be my caulk of choice for attaching the glass to the wood. I will probably not use Pond Shield since it has the possibility of cracking, I am looking for a sealant that will be more flexible once cured (I think I have gathered that Pond Coat will provide this). I think my only concern with the Pond Coat then will be its ability to hold over all three surfaces (butyl rubber, plywood, and glass) where the three meet, and staying water tight in those connections around the glass.

And any advice on the glass? 1/2inch tempered sound ok?

Thanks all,
Juice

I usually stay out of glass/acrylic thickness threads.

If you're main concern with a sealant is flexibility then the elastomeric emulsions (EE's) or polyurea are probably the best way to go. Of the EE's I have to say that Pond Coat/Liquid Rubber look the most appealing to me.

Has to be applied thick so it ends up costing a lot but the thickness itself is something a lot of people feel more comfortable with.

But yeah, the "downfall" to EE's and polyurea is adhering glass. I don't personally think it's too big of a deal but there have been some issues.

My personal concerns with EE's are the cost due to the low percent solids and required coating thickness and and also concerns about future repairability (poor adhesion) after long term submersion. Some EE's come right out and say they are not repairable after long term moisture exposure while others really don't mention it. Still, these formulations are relatively new and really until we see tanks holding water in twenty years or being repairable in twenty hears we really won't know.

But with that said, none of that would stop me from using Pond Coat or another Liquid Rubber product.

Epoxy resins and epoxy paints won't be as flexible as Pond Coat but if you read up about their performance in other applications you'll find they are plenty flexible for plywood tanks. Remember that flex in a tank also stresses the joint between framing and glass so tank flex is a problem even if you have a flexible sealant.

 

[CJH]

I think my only concern with the Pond Coat then will be its ability to hold over all three surfaces (butyl rubber, plywood, and glass) where the three meet, and staying water tight in those connections around the glass.

I wanted to comment on this specifically. Remember that you don't need the Pond Coat to stick to the glass, only to the wood and to the caulking your use.

Even if you do overlap onto the glass and that bond fails it really doesn't matter as long as the bond to both the plywood and the caulking agent is good.

If the bond between 1) the caulk and glass is water tight and the bond between 2) the Pond Coat and caulk is water tight that's all you need to worry about.

If the bond between PC and glass fails the water then only comes into contact with the other two joints. If they're waterproof you shouldn't have a problem.

Of course the bond between the PC and plywood also matters but there's plenty of information out there suggesting this is not a problem.

 

[BadOleRoss]

I am just finishing up my build and it is just slightly larger than what you are planning. As far as the glass goes, I went with 1/2" plate glass. I saw no reason to go with tempered glass and the glass I went with is plenty strong! As far as the pond coat sealing issue, PC does not stick to silicone at all, in fact, it wont even cure over silicone. PC sticks to glass until it gets wet, then it sheds right off without leaving a trace. Silicone sticks to PC but just barely! If you grab it, you can easily pull it off. I discovered all of these things while trying to get my viewing window to seal. I also broke a $210.00 piece of glass but thats another story. Anyway, I did come up with a solution to sealing the viewing window. My window sits in a frame, I had to coat the frame in waterproof fiberglass resin. Doing this allowed me to silicone the glass into place onto the resin and the paint the pondcoat onto the resin up to the silicone. The resin wet under the pond coat and inch or so. This sealed my glass.
If you go to my thread which is linked at the bottom, you can see all of the testing and results. Good Luck.

 

[RedTailKinG]

check out my thread this might help you
http://www.monsterfishkeepers.com/forums/showthread.php?t=321771

 

[john73738]

Juice,

The best advice it to do alot of research. Everyone seems to have have their own idea of what works. Me personally I am using Sweetwater Epoxy Paint. Any product that holds the water in is a good one. Don't use a product because it is the most promoted. A lot here are using the pond coat right now because it is the "new kid". From what I have read it is a great product with downfalls like every other product out there. There is no perfect product, all have trade offs.

So research...research...research

Good Luck.

Bear

 

[BadOleRoss]

check out my thread this might help you
http://www.monsterfishkeepers.com/forums/showthread.php?t=321771

Good info but the price seems a little high. I paid 235.00 for 5 gallon. Pete is also a distributor, check with him as well.

Juice,

The best advice it to do alot of research. Everyone seems to have have their own idea of what works. Me personally I am using Sweetwater Epoxy Paint. Any product that holds the water in is a good one. Don't use a product because it is the most promoted. A lot here are using the pond coat right now because it is the "new kid". From what I have read it is a great product with downfalls like every other product out there. There is no perfect product, all have trade offs.

So research...research...research

Good Luck.

Bear

Well said!

 

[CatmanJuice]

I am just finishing up my build and it is just slightly larger than what you are planning. As far as the glass goes, I went with 1/2" plate glass. I saw no reason to go with tempered glass and the glass I went with is plenty strong! As far as the pond coat sealing issue, PC does not stick to silicone at all, in fact, it wont even cure over silicone. PC sticks to glass until it gets wet, then it sheds right off without leaving a trace. Silicone sticks to PC but just barely! If you grab it, you can easily pull it off. I discovered all of these things while trying to get my viewing window to seal. I also broke a $210.00 piece of glass but thats another story. Anyway, I did come up with a solution to sealing the viewing window. My window sits in a frame, I had to coat the frame in waterproof fiberglass resin. Doing this allowed me to silicone the glass into place onto the resin and the paint the pondcoat onto the resin up to the silicone. The resin wet under the pond coat and inch or so. This sealed my glass.
If you go to my thread which is linked at the bottom, you can see all of the testing and results. Good Luck.

I was following your build for a while and have decided to use your methods for sealing and finishing my tank, especially when it comes to the glass install and sealing. I will be sure to check out your build and post some of my own info as my build progresses.

Thanks to all for the info,