siphon or not

[JayHRC51]

All,

I've been reading about overflows for hours now, and I'm confused as hell. Is it better for an overflow standpipe to operate at full siphon, or with air being introduced? By better, I mean higher flow.

Thanks,

 

[nolapete]

Are you referring to PVC overflows, hang on box type, or a built-in one with the tank drilled?

 

[JayHRC51]

Built in, drilled tank.

 

[nolapete]

It's not a siphon then. It's a drain

Air displaces water, so no introducing air doesn't help. A piece 3/8"-1/2" tubing stuck in the the drain can help though by allowing trapped air to escape quicker and subsequently increase flow.

http://home.everestkc.net/jrobertson57268/HGB/ may help with the noise.

 

[JayHRC51]

It's not a siphon then. It's a drain

My original plan was to use the method shown in the link below, with 1 1/4" bulkheads drilled through the bottom panel. But now I'm thinking that I may just use two standpipes total. One emergency overflow slightly above the normal operating height and the other being a Durso with the air hose from the top being attached to the venturi input of a small power head. If power went out or the siphon broke for any reason, the power head would be there suck off any air from the system and start the siphon back up.

By doing this, I would still have the emergency overflow in place (failsafe), plus a 1 1/4" Durso operating at full siphon.

Is it absolutely necessary to run the third "open" channel if I have a powerhead hooked up as described?


http://www.reefcentral.com/forums/showthread.php?t=1310585

 

[Griller]

Sounds complicated.

Why do you need an emergency overflow? There is no siphon when using overflows like Nolapete said so you don't need to worry about restarting a siphon. If the power fails then the excess water drains into your sump and the system re-starts as soon as the power starts up again. Water will only overflow if your sump is too full in the first place.

Here is my simple setup as an example

Plans for sump filter and overflow


Hope this helps
​

 

[JayHRC51]

so, it isn't a requirement to have that emergency standpipe just above the normal operating height? I've currently got 3-1 1/4" bulkhead fittings and I would like to use 2 holes for the drain lines to my sump and the third hole for the return supply from my pump.

I really like the idea of having that as a back up in case one drain gets clogged.

I don't mind drilling another hole. In fact, I'll have another hole for a water change drain anyway...I'm starting from scratch here and I just want to make sure that my tank has everything I could possibly need. At least as far as drain and return lines are concerned. I haven't drilled any holes yet. That will probably take place next weekend.

Also, I read that I could expect to see about 900 GPH with a single 1.25" drain. What could I expect to see with dual 1.25 drains? Would it be reasonable to say that I would get about 1800GPH?

 

[nolapete]

It isn't a requirement to have an emergency drain. It can't hurt anything, but it's a better idea to prevent the drain from possibly getting clogged in the first place. The more flow the better.

If you decide to drill for the return, be sure to put a check valve inline to stop the back flow when the power goes out. I'd advise against it though, since it limits the positioning of your return to the spot where you have it drilled.

PVC overflows painted with krylon fusion give you much more flexibility than built-in ones. I have two on my 210 in the living room painted black like the background and you can barely see them unless you're looking for them. I do have two, but I could add more easily.

Whatever you decide to do, good luck!