This pictures shows the positioning of the overflow boxes as well as my modified Durso drainpipes. The drainpipes were later tilted, but since the background had already been installed at this stage, no photos of the tilted drainpipes could be taken.

A difference in my setup from the standard Glasscages recommendation is one 2" bulkhead in each box instead of the usual two smaller ones. The above calculator also helps you determine the minimum drain pipe diameter you need. Keep in mind that it assumes you have only one drainpipe, so if you have two you have to figure out how to take that into account for yourself. Obviously one 2" pipe allows for more flow-through than two 1" pipes, simply because the hole is greater. In my system I wanted the second overflow to be redundant to create a safety margin; that is if one overflow, for reasons that I cannot even imagine, blocks up completely, I want the other one still to be able to handle the flow with ease. 2" drain pipes help a lot with achieving this goal. The drawback of 2" bulkheads is that really only one of them fits into a reasonably sized overflow box, and there isn't much else fitting in there. This was fine by me, since I wanted to limit the number of bulkheads anyhow as much as possible. If a system leaks, it is very likely to be around the bulkheads, so the fewer of these you have, the better you are of in the long term. As a consequence of having only the drainpipe bulkheads in the tank, I would have to bring my return pipes over the back of the tank, which adds a bit of head to the pump and somewhat reduces the flow rate. I am guessing that this is not a big issue, but I've never had a setup were the return pipes did not lead over the back of the tank. If anybody has done this comparison, and has some hard date of flow rates, or just some interesting observations to share, I would be interested to hear about it.

An issue that I struggled with for some weeks after the tank had been setup was noise reduction. For a tank that's set up in a dedicated fish room in the basement this might not be a major consideration, but this tank is in my living room; that is in the same place where my family eats, listens to music, and watches TV. Two 2" drainpipes with two 1800gph pump can create an infernal noise when nothing is done to stop them from doing so. Luckily I found Richard Durso's excellent web site on standpipes very early on. Durso sells standpipes, and also has a wealth of information for people who want to build their own. If noise reduction is in the least an issue for you, the site is an absolute must read.

Photo on the right: Modified Durso drain pipe with much reduced likelihood of blocking up. The drainpipes were later tilted, but since the background had already been installed at this stage, no photos of the tilted drainpipes could be taken.

I ended up building a modified version of the Durso drain pipe that in my opinion not only looks sleeker, but also has a much reduced likelihood of blocking up. My modified Durso drain pipe is build as follows. I used a 2" PVC pipe and used a metal saw to make three incisions into one end of the pipe. Then I sawed from the side into the areas between the cuts, and took the three resulting PVC pieces out. This gave me a pipe with 3 little 'feet' on one end, onto which I placed a 3" PVC end cap. The cap can be secured in place with a little PVC cement. The water can enter the drain pipe from under the cap and pass through the holes cut into the pipe into the drainpipe. The main advantage I see in this construction is that in Durso's original drain pipe a large fish that dies in the overflow box could easily get caught in front of the pipe intake thereby blocking it completely and creating a disaster for the tank. With my drainpipe, any fish or other obstacle in the overflow box would have to wrap itself completely around the pipe, creating a tight seal between the cap and the pipe. In practice, this is very unlikely to happen.

Just as in Durso's original drainpipe, my modified pipe needs a vent hole at the very top to allow air to enter the system; that is in my pipe there needs to be a little hole in the middle of the 3" cap. If this is not provided, the water level in the overflow box will fluctuate and create the 'siphon effect' that Durso describes together with the associated toilet flushing noise. The vent hole needs to be of the right size, so some experimentation is required. If you have not seen a system like this in operation, it is hard to believe how much air enters through this hole, and how well the water is aerated in these drainpipes. There is basically just foam coming out at the bottom of the pipe.

Unfortunately, despite providing this hole, my setup still made a terrible sloshing sound when in operation, much like a washing machine. After some investigating I concluded that the micron filter bags, which closed the bottom of the drainpipes, must be the culprit. This is the 'flushing effect' Durso describes, but the ends of my pipes are not only too far submerged in the sump, they are closed off by filter bags - which I do not want to remove, because they are an essential part of my filtration system. In a nutshell, they prevented the air from exiting the pipe at the bottom, and this created a backpressure inside the pipe. The air that attempted to move back up the pipe was met by water coming down and created the noise. Based on this conclusion I proceeded to create an outlet for this air in the drainpipe below the tank. I drilled the pipe and flanged on another, thinner pipe that was connected to a hose which would bring any water that ended up in there back into the sump. In another attempt, I put a Y-section in the drainpipe and worked from there, creating a larger air reservoir in the critical section of the pipe where the noise originated. To make a long story short, in the end none of these efforts were successful in eliminating the annoying noise and my wife wasn't the least bit pleased to hear a washing machine running in the living room 24x7.

Schematic diagram of tilted drain pipe operation. If you have trouble reading the text, please click on the diagram for a larger version.

In my desperation I finally remembered reading somewhere on Durso's site that the drain pipe should be slightly tilted in the overflow chamber. There was no explanation given with this comment, so I initially ignored it because it seemed easier to simply insert my drainpipe in the bulkhead than to include a small elbow section. Also, this comment is hidden somewhere in the text and when I just wanted to look it up again when writing this I couldn't even find it anymore. As it turns out, for my system this was crucial to achieve the desired noise reduction, because as soon as I inserted the little elbow in the 2" drainpipe, the tank became quieter than I had dared to dream of ever since it was up and running! I can now sit in front the tank at night when everything is quiet in the house and all I hear is an occasional faint gurgling sound and a very quiet humming of the pumps. If my almost brand new fridge in the adjacent kitchen starts cooling, it will drone out the tank by a fair margin! My wife is very fond of classical music, and she has never complained about the tank noise once since I installed the tilted drainpipes. I guess one could say I am very happy with the setup!