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Discussion Starter · #1 ·
I am going to build a PVC overflow this weekend, similar to the one below. It will be on my 29 gallon. I plan on using 2 korilia 2's on a wave timer for intank circulation, and the return from my fuge to split and get some movement down the back of my tank, behind my rock. problem is, im on a budget here. I have a pump, it is a CA 1800, says it is 400GPH @ 4' head, mine will be about 4'4". I do plan on upgrading the pump to prolly a MAG 7 down the road though.

I read somewhere that 1" drain will provide 600GPH flow, is this true, again, I will be using the overflow below, with maybe 10" added on the bottom. I do not want to much flow, no less than 400GPH, and no more than 600GPH.

If indeed 1" PVC flows 600GPH, can i just put a valve on it before it gets to my fuge, and turn it down to match the 400GPH of my pump? I was considering using 1 1/4" PVC, will this be even better?

I have searched for some sort of flow calculator, to figure out what my overflow will indeed flow, with no luck, so i am going to leave it to the experts. hope you guys can help.

 

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the overflow should only flow in the amount that you are putting water into the tank. so if you put 400gph into the tank the overflow can handle 400gph... but if you put 900 gph into the tank.. the overflow will handle only 600gph and you will have a mess... the 600 gph in a 1" pipe is the max amount it can flow as a drain. so if you only put 400gph to it. it will flow 400gph
 

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With all of the turns, I have found that a 3/4" wasn't large enough for my odysea 500 wp. So, I went back to 1" but, since you will be wanting more flow I would suggest 1 1/2 just to be extra safe.
 

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Discussion Starter · #4 ·
Black71gp said:
the overflow should only flow in the amount that you are putting water into the tank. so if you put 400gph into the tank the overflow can handle 400gph... but if you put 900 gph into the tank.. the overflow will handle only 600gph and you will have a mess... the 600 gph in a 1" pipe is the max amount it can flow as a drain. so if you only put 400gph to it. it will flow 400gph
so let me get this correct, even if my overflow can potentially flow 600 GPH, since my return is only putting 400GPH back into the tank, then the overflow in essence, will only be able to flow 400GPH??? If this is correct, then it makes sense, if this is not correct, then i am lost. essentially you are saying that as long as the overflow can flow more than the pump, than i do not need to worry about it, granted, im not going to put a 2" overflow on a 400GPH pump.
 

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ya your overflow is not going to be sucking water out of the tank on its own. it will be sucking water that is being forced into the tank from the return pump. so the overflow will flow whatever you give it up to its max of 600gph. so seems like you understand, the overflow can handle more than 400gph but will only flow whatever the pump flows.. thats why its always good to have a overflow a little larger than your return pump due to when pipes get dirty and such..
 

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lilwillywilly said:
so let me get this correct, even if my overflow can potentially flow 600 GPH, since my return is only putting 400GPH back into the tank, then the overflow in essence, will only be able to flow 400GPH??? If this is correct, then it makes sense, if this is not correct, then i am lost. essentially you are saying that as long as the overflow can flow more than the pump, than i do not need to worry about it, granted, im not going to put a 2" overflow on a 400GPH pump.
Right, as long as your return pump is moving less than the maximum rate your overflow can handle you are fine. An overflow can only drain as fast as the return can put water back in, up to its maximum rating. Being that you are DIYing the overflow, you will want to put a ball valve on the return pump side in case your overflows maximum rating is lower than what your return pump is moving, so you can back the return pump off a bit in case its too much.
 

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Discussion Starter · #7 ·
Thanks for all the help guys, i have been scratching my head over this for over a week. now that i know i should be safe for now, im going to go ahead and build it. appreciate the info. -yes
 

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Is this a siphon or an overflow? Maybe I'm not understansing the picture very well, but it looks like the siphon will just drain the water out of that inner tube until it is gone and leave your tank to overflow?
 

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Discussion Starter · #9 ·
the larger outer gray tube has holes around the top of it to allow the water to overflow past the lip and down inside of it, where the blue tube will intern syphon it. actually, that part of my design will be a lil different, but same principal.
 

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Ok, the dotted line is where the water level will remain when water stops flowing.

The siphon becomes broken near the end because of the exhaust pipe.

And as long as Tube A remains submerged under water you should not have to worry about the siphon becoming broken from that end. Also.

I think it due to back pressure, holding the water in place.
 

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Discussion Starter · #12 ·
Onlycrimson said:
Well let me put it this way, if the power goes out how does it not break siphon?
funny i woke up this morning planning on buying the stuff to build this, but your point popped into my head. I already planned on drilling a syphon break in the return lines, why couldnt i just drill a syphon break in the syphon tube as well, say an inch or so below my water level.
 

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Discussion Starter · #14 ·
do you have pics of it on your tank? How does it skim the surface water? that is the biggest concern for me, that and noise. prolly couldnt make it out to check yours out any time in the next few days, but i would greatly appreciate pics.
 

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Alright, getting pics may be diffifcult but, I'll try. They chould be up in a few hours.

My surface is skimmed twice because it's in an overflow box. for you though, you would want the water entry tube just below the surface, unless you cut some teeth into the PVC.
 

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i use to have something similar to this before the only thing i would change is move the T on the outside up a little. i had mine close to the bottom like you have it drawn when power went out i would get air in the line and brake siphon and you will have to drill a hole in the cap on the exhaust to let air in.

 

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Discussion Starter · #17 ·
Johnos said:
Alright, getting pics may be diffifcult but, I'll try. They chould be up in a few hours.

My surface is skimmed twice because it's in an overflow box. for you though, you would want the water entry tube just below the surface, unless you cut some teeth into the PVC.
since my tank is already set up, i was going to move my rock and sand out of a back corner, and put a piece of acrylic with teeth cut into the to in that corner, like a corner overflow. however, i wasnt going to glue it, just use my substrate (3"+) and my live rock to hold it in place in the corner, then i was thinking i could just do a syphon type over flow behind the acrylic in the corner, make sense? i'll try and sketch up a pic real quick for you.
 

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Still not a good idea, if you lose power that small area would drain, then you would lose syphon, then when the power comes back on your top tank would be flooded since you have no syphon to make the water go back down.
 

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Discussion Starter · #19 ·
well this *****, i am trying to have as little pipe showing in my tanks as possible, and with some of the designs ive seen, double "u", etc. it doesnt seem like i am going to be able to accomplish this.
 

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lilwillywilly said:
well this *****, i am trying to have as little pipe showing in my tanks as possible, and with some of the designs ive seen, double "u", etc. it doesnt seem like i am going to be able to accomplish this.
Haha i kind of see how it would work now, all the variables are hard to put together in your head.

Do yourself a favor and drill your tank if possible. Yes it can be done while the tank is full. You can get cheap glass cutting bit and drain the tank a few inches below drilling. Get a bulkhead and then you don't need to worry about suphons or anything. Check reef central for the threads.
 
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