So I made some standpipes, in Part One of this adventure. Up till this point, I followed exactly the directions I found for making them. But being myself, I can't help but try to tinker with something, so I had a few deviations from the design that I wanted to make.
The first adjustment I made involved the cap on the top of the standpipe. I didn't talk about this cap in the first entry on these standpipes, but the cap is a very important part of this particular design. If the standpipe had just a u-bend going back down into the water, what we'd have is a siphon. Siphons move a LOT of water, very very fast. Particularly with large pipes. This can be dangerous, because the siphon will continue draining water until something breaks the siphon. But in this particular design, it would be more annoying than dangerous--the pipe would siphon the water in the overflow out very quickly until the water dipped below the intake hole on the standpipe. Then it would suck air and make a horrible gargling noise. Not super fun.
So the cap has a hole drilled in it, to break the siphon. This allows the introduction of air into the flow of water, and means that the flow of water down the pipe simply happens because of gravity. Which is what we want here. Here's what the Durso website has to say on the subject of how to adjust the hole in the cap:
A very small, as small as I could make it (thickness of a toothpick), hole is drilled in the top of the End-Cap fitting. This allows some air to enter into the standpipe. This size air hole worked well for my setup, you will likely need to tinker with it. I would suggest starting with a 1/16 inch drill bit for the air hole in the End-Cap. If you find the water level in the chamber fluctuates quickly then the standpipe needs to suck in more air. Try a 5/64 inch drill bit to make the hole slightly larger — increasing the size if needed. Do not be surprised if you need to go as large as ¼ inch with the hole size. The lower the flow rate between display tank and sump the larger the hole size needed.
If you make the hole to large then the water level will be to high. (It should not overflow the tank as it will not get that high, but keep an eye on it). If the water level is too high you may need to replace the end-cap (they are cheap).
On the spectrum of all flow rates people might use with a Durso standpipe, mine will be fairly low. So according to this, I will need a reasonably large hole. But how large? I don't know, because I won't be able to set the whole thing up and test it for a while--at least not until I have all the pieces of the system in place. So I could've just left it without the hole, I guess, and worked on that part later. But then I read this, regarding using two standpipes in a single overflow box:
This may seem like an ideal solution but I personally don’t recommend it. It can be difficult to tune both standpipes getting the right air-hole size, etc. It’s hard to see when they are balanced or is one processing more flow than the other. If you are seeing a “flushing effect” which one do you troubleshoot?
Well, okay. But this is how my tank is set up. So I am going to try it anyway! But not without a little tinkering. I decided to figure out a way to make it easier to tinker with the hole size on the standpipes, and this is what I came up with:
I drilled a large number of holes of increasing size around the small joining piece under the cap, and then drilled the largest-sized hole in the cap itself. This way, I can just line up the hole in the cap with a range of holes underneath, and play around with which size works best for me. And if it doesn't work, well, like Mr. Durso said, the caps are not too expensive. I can go back to the drawing board if I have to.
The second modification I made is much, much more simple. The original reason I wanted a rimless tank with an overflow is because I wanted the clean look of nothing hanging over the edge of the tank. I am planning on hanging my lights, and everything else will be taken care of through the holes drilled in the tank bottom. So with all this work to make a clean look for the top of the tank, I didn't want my standpipes to be the first thing you see when you look at my tank, particularly if you're a little tall (which I am definitely not).
The solution to this is fairly easy: paint! I don't want to hide the fact that I have standpipes; I just want to make sure they aren't the first thing you notice. Goldfish are beautiful, so you should be looking at them! Krylon Fusion spray paint is used by many aquarists for in-water painting applications, and that is what I used to paint my standpipes. I decided to just paint the caps and the tee assemblies, because the bits below that will be well out of sight farther down in my overflow.
Here the parts are post-paint:
And here is what they look like in my overflow, from the back. This is a view no one will have once I have my tank set up, because that side will be against a wall.
And finally, this is a somewhat top-down view, showing how well they blend in now. I am very satisfied with this result!
So, at least for now, this part of the project is completed. I'm excited to have two whole pieces finished! Now to move on to the under-tank plumbing...