my first fuge: overflow gph vs. return pump gph

[copi]

Am setting up my first fuge, and looking into overflows & return pumps. Here is what I can't wrap my brain around: which should be rated at a higher max GPH?

It seems to me that if the overflow is higher, it will siphon the water level down and break the siphon. If the return pump is higher, the tank will overflow.

I'm looking to setup a small fuge for my 30 gal -- sort of a "practice" for the larger system I intend to setup in about a year after I move. So I guess I'm looking to move 300 to 450 gph? Thanks in advance.

 

[steve-s]

You need to be sure the overflow has a slightly higher capacity than the return pump. You can also install a ball valve in the return line to restrict the flow from the pump to get the desired return rate.

The overflow will only remove from the tank what the return pump can feed it. As long as you don't exeed that, you'll be fine. Ensure that all pipes in the water have siphon break holes drilled in them just below the water line and look for a "U" type overflow.

Cheers
Steve

 

[copi]

I was thinking something like this... Is this the correct type? In truth this is pretty much the only commercially available one I can find...

What does "continuous siphon" refer to? Thanks again.

 

[steve-s]

That is a CPR overflow which utilizes a "C" type tube and requires a pump to push water through the overflow keeping optimum performance. Personally I wouldn't recommend them, too much chance for spills.

I would look at these instead... http://www.lifereef.com/siphon.html

Cheers
Steve

 

[Phyl]

This is the one that I have on my 30g QT: Click here for eBay Auction

It seems to work OK but I'd say it is more like a 400gph rather than 600.

With my fuge I just cut holes in the sides of my fuge box and put bulkhead fittings in it. I installed 2 so that I had a backup in case the first go clogged (forget who I stole that idea from, but thanks) and then have it higher than my sump in my stand. No need for an overflow and it works great. Are you planning to overflow out of your main? Do you have a sump already?

 

[copi]

That is a CPR overflow which utilizes a "C" type tube and requires a pump to push water through the overflow keeping optimum performance. Personally I wouldn't recommend them, too much chance for spills.

Would you be able to elaborate on the differences? I've tried to read a bit -- done some searches on this site -- but I can't wrap my brain around the differences in the two models (C vs. U), or even really how they both work (it seems to me that all you need is a tube at a certain height to drain water to the fuge below, like the holes in your bathroom sink that drain water if the level gets too high; I guess the trick is getting it up and over the tank edge).

I guess I really don't even understand what I'm looking at in these photos.

Thanks.

 

[jaiden]

A C has a big box shaped gap in the acrylic. They flow a lot, but because they have so much surface area (internally) they are prone to losing siphon. This is why the "aqualifter" pumps are used to suck out the air.

U ones just use regular piping bent into a U shape. smaller holes means generally less flow. but the smaller a siphon is, the easier it is to prime.

you have to use an overflow of some sort if your tank isn't drilled. sometimes called a "weir" ... you should read up on them before you decide. regardless, I'd get one which is rated at least 30% higher (and preferably 100% or more) than your return pump. Snails like to crawl in them and if they block 50% of the flow (say there is some tasty algea on one of the two U pipes) your tank will overflow in a hurry.

 

[copi]

Also, any available on a continuous basis from a retail site (unlike lifereef.com, which appears to take orders and then build individual units)?

Thanks.

 

[steve-s]

http://www.championlighting.com/home.php?cat=416

Cheers
Steve

 

[copi]

So just to summarize:

I should buy a "U" type over a "C" type because, in the event of a power failure, the "C" type siphon will break, and upon return of power the return pump will overflow the main tank. This is not a problem with the "U" type.

Is that right?

 

[steve-s]

The problem with the "C" type overflows is they may not restart the siphon in the event of a powerfailure. The "U" style should maintain the siphon and restart on it's own when power is restored.

Cheers
Steve

 

[Brisc0]

I have a 105G dumping into a 30G sump/fuge and another 30G tank tied into those two. They all use CPR overflows with aqualifters and I haven't had a flood yet.

 

[Phyl]

Hmm.... I haven't experienced this with mine (which from what I've read is a C type v. U type. Once I sucked the air out of the airline hose I just stuck it into the overflow box where the siphon is maintained. I haven't lost siphon on it yet (LOL, famous last words). A guy in my reef club was selling a float switch which I've procured and am using on the "sump" for my 30 so that should something go wrong I won't end up with a spill. I strongly believe in safe seconds. I have one on the fuge under my main as well!

Aqualifter? What's that?!

 

[steve-s]

http://www.marinedepot.com/md_viewItem.asp?idproduct=KTALP

They are used to suck air out of the overflow tube and help restart the siphon in the event of a powerfailure.

Cheers
Steve

 

[copi]

They are used to suck air out of the overflow tube and help restart the siphon in the event of a powerfailure.

If the aqualifter is in place in event of a power failure, is a "c" type PLUS aqualifter still inferior to a "u" type? I ask because the c-type is available at my LFS, I believe.

Thanks again -- this thread has been very educational to me.

 

[steve-s]

Your choice. As you can see people use them without issue. Personally I think anything that needs "help" like the C type overflow is asking for something to go wrong. The more complicated something is, the more likely something will break down.

Cheers
Steve

 

[Brisc0]

The more complicated something is, the more likely something will break down.

Ultimately this is true. If you use the aqualifter you won't have problems with your overflow. You *WILL* have problems with your aqualifter though and will have to change it out a few times a year. I use CPR mainly cause its the only thing I have ever used. Not saying I wouldn't recommend it, but they will bite if you don't keep up with them.