Hello all 6 years ago I designed and built a 130 gallon plywood tank with three windows. If you want to see the build it can be found here.
The tank measured roughly 24x48x24 and I used fiberglass and epoxy to seal it. The tank was designed with a 3-pipe overflow system with an internal overflow draining to a 55-gallon sump. overall, I was very happy with the build and it ran relatively problem free for its whole life. a few years ago, I decided to put some pathos in the tank to help with nitrates and although it did work it eventually caused a problem because I placed the plants inside the overflow box. After a while the roots grew through the silicone that held the box to the tank the main body of the tank started leaking into the overflow box. I then built a new overflow box and screwed it into the back of the tank. This was the beginning of the end for the tank. The original overflow was also screwed in which is the cause of the failure. after removing the old box, I plugged the screw holes with silicone and went on to install the new one.
luckily, I caught the imminent failure before it happened. During a water change the other day I noticed that there was some mold on top of my water pump return line. after further investigation I found that the whole back of the tank was bowed out about 2 to 3 inches and water was seeping from the bottom seam of the plywood. I decided at that point that the tank was beyond repair and promptly drained it and moved the inhabitants to temporary living quarters.
Today I started to disassemble the tank with hopes of saving the 3/8 glass that I used for the windows. I also wanted to see where the failure was so that I can account for it on the rebuild. I started the dissection with the bottom of the tank it did come off but it put up a fight, the plywood actually separated from the fiberglass in the process. I then went on to pull the back of the tank off, the plywood was completely waterlogged and came off without any trouble. Once the back came off, I discover the smoking gun of sorts. It turns out when I did the new overflow a couple of the old screw holes did not get fully sealed and it allowed water to seep past the fiberglass and compromise the wood of the tank. When I build the tank, I completely sealed the back wall inside and out so the water was able to stay inside and destroy the wood.
So long story short I have some take away from the experience.
First off, had it not been for the fiberglass holding back the water, this would have been a giant mess that would have ended with 150 gallons of water on my floor.
Second, I need to find a way to install the overflow without using screws. If I had done that, this problem would not have happened
Last, I need to perform a closer inspection of the tank to try and catch problems before they become catastrophes.
I hope you all can learn something from my failure, I love my plywood tanks and have built three now and currently have a 300-gallon running as well. Every time I build one, I learn from the last build. As they say you learn more from your mistakes that from your success, so here is to the next mistake.
Keep building.
The tank measured roughly 24x48x24 and I used fiberglass and epoxy to seal it. The tank was designed with a 3-pipe overflow system with an internal overflow draining to a 55-gallon sump. overall, I was very happy with the build and it ran relatively problem free for its whole life. a few years ago, I decided to put some pathos in the tank to help with nitrates and although it did work it eventually caused a problem because I placed the plants inside the overflow box. After a while the roots grew through the silicone that held the box to the tank the main body of the tank started leaking into the overflow box. I then built a new overflow box and screwed it into the back of the tank. This was the beginning of the end for the tank. The original overflow was also screwed in which is the cause of the failure. after removing the old box, I plugged the screw holes with silicone and went on to install the new one.
luckily, I caught the imminent failure before it happened. During a water change the other day I noticed that there was some mold on top of my water pump return line. after further investigation I found that the whole back of the tank was bowed out about 2 to 3 inches and water was seeping from the bottom seam of the plywood. I decided at that point that the tank was beyond repair and promptly drained it and moved the inhabitants to temporary living quarters.
Today I started to disassemble the tank with hopes of saving the 3/8 glass that I used for the windows. I also wanted to see where the failure was so that I can account for it on the rebuild. I started the dissection with the bottom of the tank it did come off but it put up a fight, the plywood actually separated from the fiberglass in the process. I then went on to pull the back of the tank off, the plywood was completely waterlogged and came off without any trouble. Once the back came off, I discover the smoking gun of sorts. It turns out when I did the new overflow a couple of the old screw holes did not get fully sealed and it allowed water to seep past the fiberglass and compromise the wood of the tank. When I build the tank, I completely sealed the back wall inside and out so the water was able to stay inside and destroy the wood.
So long story short I have some take away from the experience.
First off, had it not been for the fiberglass holding back the water, this would have been a giant mess that would have ended with 150 gallons of water on my floor.
Second, I need to find a way to install the overflow without using screws. If I had done that, this problem would not have happened
Last, I need to perform a closer inspection of the tank to try and catch problems before they become catastrophes.
I hope you all can learn something from my failure, I love my plywood tanks and have built three now and currently have a 300-gallon running as well. Every time I build one, I learn from the last build. As they say you learn more from your mistakes that from your success, so here is to the next mistake.
Keep building.