# Plywood tanks waterproofed?



## tokyo (Jan 19, 2010)

I was just wondering how much of an issue there is with plywood tanks getting wet on the top or outside? Wouldn't this eventually ruin the wood? Or do you water proof everything?

thanks!


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## iceblue (Apr 27, 2004)

Unless your really sloppy with your water changes waterproofing the top of the tank and a couple of inches down on the outside should be fine.

Mine has a 2x4 rim and I water proofed it because the tank and stand are so tall I figured it would be more comfortable to lean on it when working inside the tank. I purposely left the outside of the tank unfinished to spot any leaks quickly and to prevent moisture from building up between the ply layers.


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## Mcdaphnia (Dec 16, 2003)

I would not paint the outside and bottom with a waterproof paint. That would trap water and moisture inside. Even a plywood tank that I had butting up against an all glass tank in the back had some spots that got soft because the glass panel sealed in moisture and water.


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## tokyo (Jan 19, 2010)

I was planning on staining the wood on the outside. Would that be a problem?


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## Mcdaphnia (Dec 16, 2003)

tokyo said:


> I was planning on staining the wood on the outside. Would that be a problem?


 The wood will still "breathe", so staining should be fine.


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## tokyo (Jan 19, 2010)

Thanks for the help


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## tokyo (Jan 19, 2010)

Sorry, one more question. How much do you need the glass to overlap the plywood? I would think a 1/4" would be all that was necessary, but I wanted to make sure.


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## Mcdaphnia (Dec 16, 2003)

tokyo said:


> Sorry, one more question. How much do you need the glass to overlap the plywood? I would think a 1/4" would be all that was necessary, but I wanted to make sure.


 A quarter inch might be all that necessary, but overkill is pretty common in this hobby. I have usually overlapped glass about an inch or two, or enough to reach within a quarter inch of the bottom and sides so I can squirt an extra bead in that seam. The least I've seen anyone do was a nominal 3/4", but they painted their plywood panels inside and on the edges and then glued everything together with silastic, as if they were building an all glass tank. Pretty scary looking to someone who always uses a bazillion wood screws.


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## Rhinox (Sep 10, 2009)

If I were building a plywood tank, I would take a page from the plywood boat building handbook and seal everything inside and out with epoxy or epoxy paint.


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## 98dak83cam (Jan 16, 2006)

You only need to waterproof the inside. Water should never hit the wood, let alone be in contact with it long enough to soak in. If you have a situation where the water is in contact with the wood for a long period of time you have some fixing to do.


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## Mcdaphnia (Dec 16, 2003)

98dak83cam said:


> You only need to waterproof the inside. Water should never hit the wood, let alone be in contact with it long enough to soak in. If you have a situation where the water is in contact with the wood for a long period of time you have some fixing to do.


 I think that experiences with building, using, and repairing plywood aquariums would support xxDAKxxCAM on this only sealing the inside vs. sealing up both sides of the plywood inside and out.

I would seal up the top though, since wet things sit there longer than they should sometimes. Not the outside walls and certainly not the bottom.


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## 98dak83cam (Jan 16, 2006)

Mcdaphnia said:


> 98dak83cam said:
> 
> 
> > You only need to waterproof the inside. Water should never hit the wood, let alone be in contact with it long enough to soak in. If you have a situation where the water is in contact with the wood for a long period of time you have some fixing to do.
> ...


To add to what is said above, I did seal the top lip of my tank. This was to take care of any splashes made by the fish.


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## Rhinox (Sep 10, 2009)

> If you have a situation where the water is in contact with the wood for a long period of time you have some fixing to do.


You do have that situation... its called the inside of the tank 

ok, so maybe epoxying the outside is a bit overkill and wouldn't be completely necessary, but I would do it anyways. you never know when an inlet tube or bulkhead or something is going to start leaking, and your wood might be soaked before you realize what happened. At the very least, its not going to hurt anything.


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## tokyo (Jan 19, 2010)

Thanks for all the input!

I think I'm going to atleast waterproof the back of the tank. Like *Rhinox* said, you never know when some of you plumbing may leak.


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## 98dak83cam (Jan 16, 2006)

I really would not seal the backside of the tank. Like mentioned above the wood does need to breathe, not just from any leaks, but from naturally occuring humidity. Water spraying on the back of a tank for a 12 hours is not going to bust the tank at all. By prolonged I mean a slow leaker for months. The exterior grade plywood will not fail really fast, but given time and being wet it most certainly will.


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## Rhinox (Sep 10, 2009)

No, the wood does not need to breathe. If you encapsulate all the plywood with epoxy, no moisture can get in, so it won't rot.

But to get the benefit, you need to encapsulate all the ply, like an epoxy shell. If you just do the back, what about water that runs down the back and seeps under the bottom?


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## Mcdaphnia (Dec 16, 2003)

Rhinox said:


> ...
> ok, so maybe epoxying the outside is a bit overkill and wouldn't be completely necessary, but I would do it anyways. you never know when an inlet tube or bulkhead or something is going to start leaking, and your wood might be soaked before you realize what happened. At the very least, its not going to hurt anything.


The point made was that epoxying the outside* is *going to hurt something. Humidity and moisture need a way to exit the plywood and if it's sealed on both surfaces, water will be trapped in the wood and will cause damage. If you drill the tank, paint the inside of the hole, not everything in sight.


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## Coln (Dec 17, 2007)

I hav't sealed plywood outside of my tank, if you do get a problem it will be
easier to find with plywood thats not sealed outside plus any splashes of water
will evaporate off the tank pretty quick and not do any harm, col


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