While seam failures are rare, they do happen. Usually you will see a bit of seepage, as Toirtis mentioned as the first sign. This doesn't mean that the seal will give way, but, that the water has found a spot where the silicone has a void, and there is a spot in the joint that is open. Where you see the water won't necessarily be where the actual problem is. It can get under the inner seam and travel to a spot in the joint where it can leak out. I did have a friend, though, that had the whole front bottom seam give way in short order. He had to hold the fromnt of the tank in while they drained the tank. It started as a leak, and very quickly, the entire seam started to give way. That is a very rare occurrance. That is one of the reasons that all my tanks are in the basement around the floor drain.