1. Fully submerge the full siphon otherwise you get horrible sucking sounds. At the sump, don't submerge the end more than a couple inches otherwise you won't get the siphon started.
2. Yes, the secondary drain sets the level (sort of). The main siphon handles most of the flow, so with somefine tuning IT sets the level of water in the overflow (if the flow in = flow out, there is no change in water level) but if set this way it's easy to cause fluctuations. Decrease the flow through the main siphon with a gate valve until water JUST starts to trickle into the secondary over flow (thus the secondary effectively sets the height of water in the overflow box). If you have the bulkheads on the bottom of your overflow box (ie. you have risers coming up vertically from the bulkheads), I would set the secondary overflow a little bit higher than the entrance to the main siphon. This gives you a bit of leeway if you cause a fluctuation (like sticking your arm or a bag of frags in the tank) before the water level in the overflow box gets down to the main siphon and makes horrible sucking sounds.
3. I have my emergency drain and a straight pipe coming up from the bulkhead below (no elbows or anything). The end of the emergency is about 2" higher than the entrance of the secondary (so about 1" higher than the middle of the T I use for the secondary) and is about 1" higher than the operating height of the water. Again, this gives some leeway in terms of fluctuations so the system doesn't flip out if you stick your arm in the tank.
4. The main siphon is closed (as in no air can enter the pipe), so nothing special there. I'd add a strainer if you don't have teeth on your over flow (I had a cleaner shrimp who used to ride that water slide continuously until he took one ride too many). Secondary and emergency pipes... I wouldn't bother putting strainers on them. There's little to no flow through them to actually suck up critters (though they could crawl in) and they are basically your "Oh S***" buttons, so my thinking is to have as little restriction on them as possible. Just my opinion, others may differ.
In terms of special piping on the secondary, you just need an air tight cap on the end of the pipe with a hole drilled to fit a piece of airline tubing into. The tubing is bent over and set just above the water line in the overflow. If the water rises to plug the end of it it will cause the secondary to become a full siphon and it will literally drain your overflow like flushing a toilet (Very cool to watch... errr, the overflow, no the toilet).
Unfortunately, this is the only pick I have handy of my overflow. If you need more, let me know.
03-09-2012, 06:02 PM
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