Odd question

[labatt]

How exactly are pump flow rates calculated? Is just output or total flow? I was thinking, since a power head or pump is pumping the same thing in the same system wouldn't the flow rate be kind of doubled if its calculated only on output?
IE- My return pump in the sump pushes 500g/hr up to the display, that in turn makes another 500g/hr go through the overflow so it would kind of be like 1000g/hr. Same with a power head, if the out put is 500g/hr then if takes in 500g/hr as well so it would actually be moving 1000g/hr. If they are calculated on total flow then the question doesn't even really exist.

[BeanAnimal]

A pump is "rated" by how much water it can flow with a given amount of resistance. The resistance is "head pressure". Different styles of pumps are capable of producing different amount of pressure. The greater the pressure a pump can create, the more head it can push against.

Power heads are not good at pushing water against head pressure, return pumps are.

In any case if the return pump pushed 500 gallons up to the sump every hour, then your flow is 500 gallons an hour. What comes in must go out. The same with your powerhead. If it pumps 500 gallons per hour, that is all you get.

Think of it this way. The minute hand leaves 12:00 oclock and travels around the dial back to 12:00. One minute passes, not two, even though the minute hand "goes out and comes back in".

So anyway, it does not matter of you measure the flow from the input or the output. What goes in must come out. Water is non compressible... so for every ounce that enters the pump an ounce comes out.

Hope that helps.

[labatt]

I understand that, but Im still not clear on the thought. Look at it this way- you have X pump puming Y amount of water from container A to container B. The pumps rated flow is Y (adjust for head pressure if you like, it doesn't matter)You are moving Y amount of water in both containers so the total amount of water moved by the pump would be Y+Y. In the aquarium there aren't 2 seperate containers but you still have two ends of the pump so couldn't you sort of say that its actually moving Y+Y water? Or ever better worded the flow in the tank is Y+Y, since thats not how a pump is rated? I know its kind of retarded but it almost makes sence to me.

[bill9999992]

You forgot how much TIME it takes to fill container.

Flow rate=How much TIME it takes to move liquid over X distance.

[alizarin]

You CAN look at it that way - that you're moving Y into the pump and Y out of the pump (from container A to container B). But if you're saying that then you could also say that it's Y in, Y out, Y out one mm ahead of the pump, Y out 1/2 inch ahead of the pump, etc to infinity until you have total water moved=infinity. But, that's not a useful way to look at it for most of us. Looking at it that way would be useful if you were studying differential equations to calculate water levels in different containers at different times. The way I think people look at it is that a pump moves a stream of water and Y is the flow rate at the single point that intersects the pump. And as far as out of container A and into container B - I think people see container A and B as one volume of water as soon as they are connected by the pump.

Why do I always feel like I've been smoking weed when I talk about math?

[sarduci]

Empty container A, full container B. If I pump all of B into A, that gives us a flow of X. But what you are saying is that if container A is full also, since I pump B into A and the same amount has to jump out of A to make room, it all of a sudden doubles the flow?

If that is what you are saying, then simply connecting a 500gph pump to 10 fish tanks cascading one into another would actually give you 10,000gph since each one would displace and move 500gph per step down. Add another 10 fish tanks and you'd double it again.

No, your math is incorrect or I have several Maxijet pumps that push 1,000,000gph for sale, with free upgrades to bigger pumps every time you add another tank to the loop.

Displacement and flow are two different things.

[papagimp]

LOL, oh that was too good. I think I want to buy one of those million gallon per hour pumps!

[labatt]

Well thanks for the standard rude answers that so many people love to give here sarduci.

[joestreich]

i am not sure if we can answer your question without sounding rude. No one wants to hear that they are wrong...but it happens to all of us. Your formula is just wrong that's all. I thought the way that he explained it was very good and easy to understand. Thanks for bring up the question....and thanks for all the answers.

[PatMayo]

I agree Joel. Things come across as they are not meant sometimes. I would not sweat it. I doubt that Sarduci meant anything by what he said. Take a chill pill and relax labatt.

Regards,

Pat