Confused about waterproofing options,120 gallon plywood tank?

[SteakForLunch]

Hello,first post here. So I had a plywood tank in mind for some time now. The box,I made out of 12 mm plywood and the braces with 19 mm plywood. The next part is where I have been having nightmares about. Waterproofing. I know just about all DIY hobbyists use epoxy to waterproof plywood. But I can't find any "marine" epoxy resins where I live, not even on Amazon.(I live in India). All I can find is araldite epoxy adhesives, it says on the box they are waterproof but I'm sceptical if it will resist complete immersion? I was wondering, can I use silicone over the entire surface of the tank? Seams an all? I have around 3 tubes of unopened silicone,I had them lying around from a previous filter build. But I haven't found any tutorials or threads on applying layers of silicone to waterproof plywood. If it seals joints,it should seal surfaces too right?

By the way,the tank is only temporary,a 120 gallon for holding my Oscar. He grew a bit too aggresive the past few days,I had him with my turtle. I'll be getting a 375 gallon acrylic tank in the next few months and the plywood was basically free,we used it previously for construction. It's also marine grade,if it helps. Any suggestions anyone? Thanks.

 

[frasertheking]

You will find someone selling epoxy resin for sure. Check what ever your version of ebay is, bog standard epoxy has been showing up pretty cheap. I doubt silicone would hold up but you do not need "marine epoxy" the main difference is just the final strength and UV resistance. Most epoxy will cure inert.

https://dir.indiamart.com/impcat/epoxy-resins.html just what I found of google

 

[SteakForLunch]

I did find casting epoxy resins but I'm not sure if all epoxy resins are completely waterproof and suitable for immersion? Also,why do you think the silicone won't hold up though? Thanks for the reply by the way.

 

[frasertheking]

I did find casting epoxy resins but I'm not sure if all epoxy resins are completely waterproof and suitable for immersion? Also,why do you think the silicone won't hold up though? Thanks for the reply by the way.

No worries, casting epoxy is different from construction epoxy so I am not sure if it would work. I feel like the silicon would not be very hard wearing and would tend to delaminate from wood. you could fit a pond liner but that would be a bit of a hassle, you might be better off asking construction companies in your area or universities if they have a source. I managed to get a hold of the rep for a UK brand and he was willing to sort out supplies to people who had a good idea of what they are doing. I would start emailing the above as well as searching for the companies that make epoxy and trying to get an email or number for their reps/ sales people.

I know India can be rough on imports but that is also an option, many companies sell epoxy on alibaba and such. To your question on waterproofing all construction epoxies will be waterproof unless you have used something like alcohol or acetone to thin them.
i say construction epoxies but any epoxy used for bonding/ laminating should work. West coast is the most popular because they have put a huge amount of work into community outreach with guides and making their epoxy as user friendly as possible but the unbranded stuff kicking about from china works fine too.

 

[SteakForLunch]

Funny story about pond liners, I actually replaced pond liners twice on this one. I used a tarpaulin as an underlayment and topped it off with the liner. It's was an HDPE geomembrane,two days in and my Oscar chewed through the liner in multiple places. I suspected it was the silver dollars who did this,so I replaced the liner and put Albus,The Oscar,all by himself. The very next day,there were holes in the liner. There was no leakage as I had sealed the seams with some silicone.

I did get my hands on some araldite standard epoxy adhesive, but it's going to be a tough one to work with. It's consistency much thicker than honey,it says it's for industrial use. Do you think this might work? Also would I have to scrape all the silicone or will epoxy adhere to it?

 

[frasertheking]

Funny story

I did get my hands on some araldite standard epoxy adhesive, but it's going to be a tough one to work with. It's consistency much thicker than honey,it says it's for industrial use. Do you think this might work? Also would I have to scrape all the silicone or will epoxy adhere to it?

That is crazy, perhaps you could put polycarbonate sheets over the liner? You will have a hard time with the adhesive. you can thin epoxy but it will no longer be waterproof. heating up the epoxy will shorten its pot time and I assume being adhesive it has a short work time which heating up will only decrease. heating epoxy reduces its viscosity. I bet that many people are using epoxy in construction in India. Motorbike and car parts are often epoxy infused, people making water tanks or industrial water storage will work with epoxy on a daily basis. Industrial suppliers are your best route.