Overflow/Return question

[KirbyBTF]

Im setting up my sump tomorrow and have made a giant list of all the pvc I need. Everything looks good to go. Except I can't quite grasp something...

The overflow I got is rated for about 900gph (hang on U pipe style)
http://www.amazon.com/Aqueon-34508-Hang-On-Overflow-125-Gallon/dp/B0036RZKPY
The return pump is rated for 496 gph
http://www.amazon.com/Aquatop-NP-306-Aquarium-Submersible-Pump/dp/B006K4IQ3I

I just can't for the life of me understand how the sump isn't going to overflow with the return pump only pumping out 496 gph, while the overflow is at full syphon.
I had planned to get a ball valve to restrict flow if need be, will that solve the issue? Or does the return pump dictate how much flow the "full syphon-ed" overflow box is getting?
Please help me figure this out, maybe Im missing something big here idk. BTW Its a 40b, going to be using 1" pvc for return and overflow

Parts list:
90 degree 1 1/4" x1
90 degree "street" 1" -> 1 1/4" x1
90 degree 1" x2
90 degree "street" 3/4" -> 1" x1
Union 3/4" x1
Union 1 1/4" x1
PVC 1 1/4" x1
PVC 1"
Ball valve 1 1/4" x1

adding picture in a sec of my sketch up (please critique)

Edit:

Sorry if the picture makes no sense, totally makes sense in my head.

 

[Percula9]

Even though your return pump is inadequite, a valve on the drain is the only way to control it.
The pumps rating, is the flow, at zero head pressure. How many feet up does the pump have to pump?How big is your tank? You will have to get a bigger return pump that is closer to the drain flow.This way your water turn over rate is high enough to filter your tank.

 

[KirbyBTF]

Tank is 40g, I read a 400gph was minimum for my size tank and LFS confirmed that. I was planning to compensate the lack of flow with powerbeads. Is my 500gph not enough?

 

[KirbyBTF]

Also, 2ft of head on return.

 

[Reef Mortician]

Your overflow will only drain what your return will put out. The sump will not flood. What you will need is a gate valve on your drain if your doing a full syphon. Mind you I would tune it so a trickle is flowing into the relief drain.

 

[Isaacs55]

Have you planned on a overflow method yet? Herbie? Durso? Or BeAnAnimal drain? It seems like you only have 1 drain and 1 return? With this setup you're going to have more problems then just worrying about the sump overflowing. Your going to get loud gurgling noise issues, constantly trying to dial it in way too many times, running the pump dry if you over dial the gate valve.
Try looking up the 3 methods I mentioned and see witch works for you. Have the same tank as you and a 20 gallon sump. My pump is also rated for 725 gph and have 2-3 feet head loss so that puts me at about 400gph. I have a herbie method which is 1 drain full syphon and an emergency drain with a trickle to make it dead silent. I have a gate valve and ball valve on both my drain and return line. Ball valves are there for shut off only so I won't have to keep dialing in my gate valves after maintenance.

 

[fishgate]

You really can't get there from here. Your pump is under-powered for a full siphon drain. Get a Jebao DC pump or some other pump that puts out 1200GPH+. As others said, you need at least 2 drains for a full siphon and three is better.

For your parts list, get 3x whatever you think you need and return the rest. Also get yourself one of the scissor style PVC pipe cutters. You'll also need some sand paper to smooth the burr off the cut. If you decide to go with full siphon, only the full siphon drain needs a valve, the others don't. The pics you see might show a valve on each.

 

[Vinny Kreyling]

You can't drain more than you put in!
Unless you use a Herbie or Bean Animal drain there is no need for a valve on a drain but there should be one on the pump return.
NO check valves here either!
Suggest some more reading on what drain you want to use.
Both have threads here on RC.

 

[KirbyBTF]

I'm using a hob overflow, drilling isn't an option unfortunately. The link to the overflow box is in the first post.

 

[billsreef]

I'm using a hob overflow, drilling isn't an option unfortunately. The link to the overflow box is in the first post.

Vinny nailed it. Think of the overflow as rated for UP TO 900 gph... aka it's maximum capacity. It will work just fine at a lower rate, which is determined by your pump.

BTW valves on drains are a bad idea. To easy to clog, and too easy to close down, leading to tank overflows.

You can't drain more than you put in!
Unless you use a Herbie or Bean Animal drain there is no need for a valve on a drain but there should be one on the pump return.
NO check valves here either!
Suggest some more reading on what drain you want to use.
Both have threads here on RC.

 

[KirbyBTF]

I decided to just do a hob filter for a while. Thanks for all the info though, after Christmas I'll probably get the hob overflow going, I'll be leaving for 2 weeks and hob overflows make me nervous.

 

[Vinny Kreyling]

Took a look @ the pump, I would suggest replacing it with an Eheim of similar specs.
Proven reliability is the main reason for this suggestion.
Where are you located?

 

[bhbell]

I've used the over the top hang on siphons you're talking about. They worked fine with one exception. If the power goes out you need to have a way to apply vacuum to the tube to restore the siphon before the return pump can overflow the rim of the tank. I used a Maxijet with the air inlet of the venturi connected by air hose to the highpoint of the siphon tube. It'll blow small bubbles till it draws enough air out to restore siphon. You have to pay attention to this or you can wind up with water on the floor or even worse if you also have an ATO.

 

[KirbyBTF]

Took a look @ the pump, I would suggest replacing it with an Eheim of similar specs.
Proven reliability is the main reason for this suggestion.
Where are you located?

Im in GA. I did some math and id only be getting around 200gph from that pump after head loss and the 90's from the plumbing so yea I will definitely have to upgrade it. I did however find a neat DIY overflow and ill be posting a pic here in a sec to get opinions on it.

 

[KirbyBTF]

I actually like the look of this better than an overflow box

 

[bhbell]

Without an overflow box of some type you wont have a weir. The weir aids surface skimming of the film that tends to form on the water. You would still have the issue of having the re-start of the siphon after a power out. I assume there's a 1/4 OD tapped in somewhere to do this. You just need to make sure you restore siphon faster than your return can raise the level in the tank to overflow following a power out.

 

[Vinny Kreyling]

Lifereef if you go with HOB.
The one you show will NOT start again after power failure.
They say Eshopps is good but I have no experience there.
IF you were local I could hook you up but it would be very expensive to ship what I have.

 

[Isaacs55]

CPR overflow boxes from marine depot restart after power failure so maybe check those out

 

[Vinny Kreyling]

Unless the design has changed you need a pump to suck out any air in the chamber or they stop working on a regular day.

 

[KirbyBTF]

Well looks like I got the wrong overflow box then lol. Aqueon had higher reviews so I opted for that one. I heard lifereef is the way to go, but it's also twice as expensive. Get What you pay for I guess.

Could add a float switch to dt for the return pump, and a check valve in return pump plumbing. Might not be as reliable but I do prefer the pvc variation to the weir.

And what did you mean by a 1/4 OD?