Question for the math guys

[john73738]

Reading the pipe flow charts,

size _GPM __GPH
1/2 = 2.50 = 150
3/4 = 5.63 = 337.5
1.0 = 10.0 = 600
1.25=15.6 = 937.5
1.5 = 22.5 = 1350
2.0 = 40.0 = 2400


With my overtank filter, am I reading this right that 2 1" pvc drains will not be enough to drain 1400-1600 gph at a drop of about 4" plus a tee at the end. Or should I be looking at another chart.

BTW here is the basic design, Many changes have been made, but will not effect the draining

 

[ikevi]

I am confused, you say you are doing an overtank filter, which would mean you are mostly limited by your pump rate with your tubing at 1' diameter. (Since you would only care about the pumps head height to pump water above your tank.)

But then you go on and say you are dropping ~4 inches, and have a T which makes me think you are doing it as an overflow with a normal sump instead? (So what is this a sump that is 4 inches bellow the tank?)

Then it comes down to where the bulkhead is located in the hight of the tank. IE you need to know the pressure on the side that the water is flowing from. (Either due to gravity and water pressure, or due to the pressure that the pump will supply.)

Once you know that they you will know your total flow rate.

But basically what it comes down to is for a 1' diameter pipe you are going to need about 1 psi of a pressure drop across 4 inches of pipping.

To play around with numbers I use something like:
http://www.pipeflowcalculations.com/pressuredrop/index.htm

 

[john73738]

Here is what the tank looks like

The filter is the box on top. I will be using 2x 750gph pumps to pull water from either end of the tank. The water will drain back into the tank in the middle that will be a wet dry. Head loss will be minimal due to the fact that it is only lifting the water 12"

Will check out that resource you posted tho..

Thanks

 

[Pharaoh]

You are correct. You will want to drain the tanks using 1 1/4" PVC or larger.

 

[john73738]

Thanks Pharoah... That's what I thought/Afraid of.... I ordered 1" bulkheads... Oops

Oh well, will order the 1 1/2" to be extra safe not to overflow the filter.

 

[ikevi]

Ah I get you. So you were talking about the piping from the overflow back into the tank.

Then just as Pharoah said you need a bigger pipe. (IE to get 1 psi on the drain of the sump you would need ~2 1/4 ft of water above it.) And with your setup you will have at most ~.43 psi when completely full.

 

[john73738]

Cool guys,

Thanks for the help.

Solution........

Ordered 2 1 1/2 " bulkheads. So the drain will be 2 x 1" and 2 x 1 1/2" .

That should do the trick. Here is a little graphic to show what I am going for. Hope this works, because it it does then I will be applying it to all my tanks in various sizes.

 

[dawnmarie]

I like your design and I have a curiosity question. Are the pumps going to be installed above the main tank ?
Will they be "sucking" the water up the length of the inlet pipe not to mention thru some form of prefilter ?
The reason I ask is pumps prefer to blow , not suck.(Keep it clean people)
Perhaps submersible pumps at the bottom of the main tank would be a better option.
Oh Yeah, don't overlook the minimum vertical pipe length required to achieve max flow for any given pipe size.

Min. Vertical Length
1/2 = 2"
3/4 = 5"
1.0 = 9"
1.25= 14"
1.5 = 20"
2.0 = 36"

Thanks CHOMPERS

 

[john73738]

I know that does not show in this picture but the pumps are only about 1" above the water. I placed them for ease of maintenance. Will see how it works and let all know.

I caught the minimum length as an after thought, that is why I am going with 5 returns. 3x 1" and 2x 1.5" just to be sure.

This may turn out to be a complete disaster but I will not know until I try.

Thanks for the input. Working late all next week, hope to get a lot done next week.

 

[john73738]

I like your design and I have a curiosity question. Are the pumps going to be installed above the main tank ?
Will they be "sucking" the water up the length of the inlet pipe not to mention thru some form of prefilter ?
The reason I ask is pumps prefer to blow , not suck.(Keep it clean people)
Perhaps submersible pumps at the bottom of the main tank would be a better option.
Oh Yeah, don't overlook the minimum vertical pipe length required to achieve max flow for any given pipe size.

As was stated in a previous reply the pumps are drawing the water rather than pushing it. So you got me thinking and I have redesigned the plumbing to such. I think it will be more efficient, only 2 bulkheads for intake, and more standing water for bio filtering. Plus if my theory is correct easier starting.

This is just an idea, and may fail miserably, but will not know until I try.