How to size a pump to your tank

**terrors r us** · 09-09-2008, 10:28 PM

Originally Posted by Dr Joe;2115173;

Ok, first off terrors r us, it's stated in feet of head not heads

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If your pipe is not undersized for the pump (see manufacturers spec) and is horizontal exclude it. I add elbow, solenoids, spray bars etc to the equation. Plus how high it is from the sump/filter to the top of the tank.

Pumps are spec'd out @ max head as where flow stops (so a relatively useless spec to most people).

The pump you specified may be a little too strong for your situation, the next smaller isn't that much different so check electrical usage and go with the most efficient one.

I hope your documenting your build to share with us

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If you have other questions just start a thread in the appropriate section for a fast response.

Good Luck and keep us posted,

Dr Joe

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Thanks, I am still doing research due to ,I would like to add my breeding tanks and nursery tanks to this filtration system....keep you posted...

**Rivulatus** · 11-18-2008, 10:29 AM

What a great thread! Thanks so much for going to the trouble to explain this. I was just going to ask about sizing a pump to my 500 gallon set up, and what do you know!? There's a fantastic sticky on it. :-)

**doug08** · 12-13-2008, 8:49 AM

I learn something new today. I never realy gave much attention to something as inportant as sizizng the right pung for my tank. your article is informateve and helpfull thank you

**Finalfire9** · 12-17-2008, 12:17 PM

Originally Posted by Toodleypops;2179211;

i always just get double the size of my tank

thats weaksauce, 2 overturns a hour is pretty low, 7-10 is recommended. on overstocked tanks i run 20 overturns a hour

**KYeasting** · 01-28-2009, 9:48 PM

I would like to add one more slightly geeky tidbit to the math everyone has provided here. For the most part, as long as you avoid abrupt turns, such as 90deg. elbows (try using some rubber tubing or smaller angles such as 45deg. or 30deg.) you have little worry

. Frictional losses along the pipeline are negligible in our cases (we aren't laying down mile after mile of tubing for our fish tanks, we're using many feet....). The main concern is the elevation you must overcome. If the top of your tank lies 8 feet above your pump, 8' of head plus a little more should be counted on (you will lose some in the bend but not nearly what you'll lose compared to elevation).

In Bernoulli's energy equation shown in the pages from the hydraulics book, you have 3 components to the total head: Pressure head, Elevation (potential) head, and Velocity head. These 3 items come into play along different points in the piping system although the TOTAL head (sum of pressure, potential and velocity heads) remains the same (minus the losses, of course). Looking at the system from the pump beneath your tank towards the top, these items are as follows: The pressure head will be greatest as you leave the pump; the pressure will drop to 0 as you reach the top. The pressure head will be traded off for elevation head and minor losses. Since the pipe diameter is constant, the velocity should be the same throughout the system. Your pressure head will drop to 0 as you leave the piping system and enter the tank (if your tank was under pressure it would have to be a sealed vessel).

So when you chose a pump, take a pump that provides a head greater than the height from your pump to the top of your tank AND can provide the volumetric flow you require!

I'm done giving people a headache now.

**zennzzo** · 01-29-2009, 6:39 AM

CHOMPERS...
with the design of the magnetic drives on the centrifugal pumps we use in the Aquarium industry, does the wattage change with different loads? Or because they are centrifugal, the wattage is constant and only the output changes based on headloss...

**CHOMPERS** · 01-29-2009, 1:42 PM

It does change, and it is pretty squirrely. I went looking for one of the graphs, but I can't find it. When I do, I'll post it here.

**zennzzo** · 01-29-2009, 2:38 PM

Originally Posted by CHOMPERS;2712839;

It does change, and it is pretty squirrely. I went looking for one of the graphs, but I can't find it. When I do, I'll post it here.

Good...I seen a graph on the Dart pump but I figured it was because the impeller was direct drive off the armature of the motor...there is a sweet spot where gallonage and draw were at an optimum...

**CHOMPERS** · 01-29-2009, 4:02 PM

That's it. I was stuck on Rio pumps and they just have crappy listings at various heights.
The sweet spots appear to be where the two lines cross, and at zero head. However, notice that the Watts scale doesn't go to zero. Where the lines cross is actually an illusion (it keeps tripping me up). If the Watts scale were started at zero or any other number, the red curve would travel up or down and make the point of intersection change.
After the maximum current draw, (to the right) is where you start getting extra flow for free(ish).

**specialized002** · 01-30-2009, 1:18 PM

I'm new to this hobby and I'm pretty handy with building things. I was looking into filtration and rather than spending all that cash to buy a fx5 I want to build my own sump system. I have a 150 gal tank, the guy I bought it from gave me a ehiem 2215. My question is this, I'm reading the post and still don't really understand it completely. If I were to build a sump, from what I get, I'm going to need at least a 1" drain and I'm unsure of a pump size and return pipe size. If you could give me a ball park range it would be greatly appreciated. Thanks for your time.