# DIY HOB overflow question



## TypeYourTextHere (Apr 20, 2011)

I am planning on building a HOB overflow for my tank. The only problem I am having now is making sure I have calculated the GPH correctly. Basically The way I drew it up(I don't want to take credit for the design, I copied it from another forum) it has a "chamber" that measures 3 3/4 inches x 1/2 inch instead of a "U tube". If I am correct the chamber is the equivalent to a 1 1/2 inch diameter pipe. I calculated the inlet of the chamber to be 1.875 inches. I used another calculator to convert the area of the square to the area of a circle which came to be 1.545 inch diameter, or a 1 1/2 inch pipe. Is this correct?


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## Meshuggahn (Jul 31, 2011)

Your math adds up. The area of your 'chamber' is 1.875 inches squared. The area of a circle is PiR^2. This comes out to a radius of .7725 inches. Or a 1.545 diameter.


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## TypeYourTextHere (Apr 20, 2011)

I was hoping I did that right. It has been 20 years since I took a math class. Now the only question is if my overflow is going to be able to handle 650 GPH. I never thought I would be doing this kind of math for "fun".


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## Meshuggahn (Jul 31, 2011)

I'd imagine you will be fine unless you are taking a round about trip to the 4th floor and back or something crazy. Good luck with your project.


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## TypeYourTextHere (Apr 20, 2011)

I don't know what I was thinking when I posted that I wasn't sure if the overflow would be able to handle the 650 GPH I am gonna push through it. The way I have it set up it will be the rough equivalent of a 3 inch pipe. When I get done fabricating this thing I will post pics and what not (if I ever can get started on it).


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## bigcountry10 (Sep 24, 2011)

diameter of pipe = how many gallons pipe can handle per hour
.5" = 90 GPH
.75" = 220 GPH
1.0" = 375 GPH
1.25" = 580 GPH
1.5" = 840GPH
2.0" = 1500GPH

So your well within your range


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## TypeYourTextHere (Apr 20, 2011)

Yeah, I would say I am going to be fine. If a 1" pipe can handle 375 GPH I can cut the overflow in half the way I currently have is drawn up. As it stands i think the Max GPH that it can handle is probably 1800+ GPH which is far beyond what would ever be pushed through it.


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## TypeYourTextHere (Apr 20, 2011)

*Re: DIY HOB overflow issuse*

Okay, I am extremely frustrated at this point. I have built my overflow, well half of it, and it cant even handle a gallon of water dumped from a milk container directly into the pipe through a funnel. The siphon u-tube keeps getting air in it when water is moving through the overflow but not when there is no flow. I have tried to test it in a bucket that is being fed by the bathtub faucet and it can kind of keep up but still has trouble. What am I doing wrong?

Here is a picture of what I have so far.


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## jrman83 (Jul 9, 2010)

This place will fix your problem: CPR AQUATIC, INC - CS Overflows


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## TypeYourTextHere (Apr 20, 2011)

jrman83 said:


> This place will fix your problem: CPR AQUATIC, INC - CS Overflows


Actually that place will give me more problems being as I don't have or would I spend $120 on an overflow box.


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## jrman83 (Jul 9, 2010)

TypeYourTextHere said:


> Actually that place will give me more problems being as I don't have or would I spend $120 on an overflow box.


Just trying to help out.....

They were the ones I used to use.


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## TypeYourTextHere (Apr 20, 2011)

jrman83 said:


> Just trying to help out.....
> 
> They were the ones I used to use.


I wasn't trying to be rude, but there is a reason why I am making an overflow opposed to buying one. It cost me about $20 after everything is said and done to make it.


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## aerospot (Jan 7, 2012)

I went with this design. Works Great!
Dramatic AquaScapes - DIY PVC Overflow - Page 1


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## darkyputz (Nov 18, 2015)

How did it end up?
I am building the same/similar set up...just not with the upward pipe in the tank...mine is just looking down in the tank side...
And i needed 2 of 3/4 inch pipe versions to get the job done...


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## welok (Jul 20, 2015)

darkyputz said:


> How did it end up?
> I am building the same/similar set up...just not with the upward pipe in the tank...mine is just looking down in the tank side...
> And i needed 2 of 3/4 inch pipe versions to get the job done...


If I had to guess, I would say that's one of the reasons you get as much air in yours: with the longer pipe, and keeping it full of water, there is less (but still there) chance of it sucking in bubbles, which then might not get pushed through... 

Also, using larger diameter pipe will increase the GPH and help force the air through, though that would also mean you need a stronger pump, which might not be worth it...

On a DIY overflow, I would put the return as far away from the intake as possible, especially if you have the return above the water level: having the return above the water level will be like a HOB filter, pushing air bubbles into the water.


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## darkyputz (Nov 18, 2015)

The return is in the second tank...they are connected by to pipes...and the bubbles might come from my powerhead making super fine bubbles in the water...
But i added an automation to it to get the air out of the bow now...
But still not sleeping through smile


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