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Am i calculating actual flow right ?

G

Gorillastomp

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Joined
24 Jun 2021
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183
Location
Canada,Quebec
Today i wanted to calculate my actual pump flow.

I have lowered water so i can set a 2 tapes on the glass at 1 inch / 2.5 cm apart. Once the water reached the bottom tape, i've turn on the pump and calculated the time it took to reach to top tape Which is approximatively 1:05 min.

Interior tank size are 83in(210cm) x 25in(63.5cm) x 25in(63.5cm) which with the 1in (2.5cm) height gives a volume of 2075 in³ / 34 000 cm³.

2075 in³ / 34 000 cm³ = 9g / 34l

so 9g * 60min(rounded the 1:05 to 1 min) = 540 GPH / 2044LPH

The pump is rated at 2400 GPH / 9084 LPH.

So is this correct and my pump is losing + 78% of its capacity ?

I am using a sump so there is no media/filtration blocking the pump flow. The pump is pumping into my 20in cerges reactor to the display tank.
 
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Seems crazy too me, i guess the original rating is way lower than what is stated. I will need to test that out.

I thought i had at least 5x turn over ending up i have less than 2x lol.
 
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What pump is it?

Some pumps will state rated flow at a certain head height, but most don't, they just state the flow as measured (or not in some cases) directly at the output with 0 obstructions and no head height.

Head height kills flow rate quickly on even the best pumps, add in a reactor and I can easily see an 80% reduction in some cases.
 
OK so These are the Spec of the pump : 2700 GPH (thought it was 2400), H-Lift max 14.8 Feet

It has to uplift water 5feet higher but the water path way is around 10-11 feet, has 2 x 90 deg elbows at the reactor for the in and out plus a 83inch output with evenly spaced holes(can't remember the name of this atm), so this might be the issue ?
So what would i need to have more flow ?

They sells a 9000GPH pump with and H-list MAx of 26 feet but the outlet is 2in, will it reduce the flow/damage de motor if i use it with the current 1in pipe ?
 
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The narrower the pipe the more it restricts flow, I wouldn't use 1 inch pipe on a pump with a 2 inch outlet

I know some of the guys who use reactors split their return flow so that a percentage of the flow goes through the reactor and the rest bypasses it and that helps to keep the flow rate up. Not my area of expertise though.
 
Gorillastomp said:
5feet higher but the water path way is around 10-11 feet, has 2 x 90 deg elbows at the reactor for the in and out plus a 83inch output with evenly spaced holes(can't remember the name of this atm), so this might be the issue ?
Click to expand...

All these things will reduce flow, head height and the elbows being big ones.
Gorillastomp said:
So what would i need to have more flow ?
Click to expand...
Can you not just add a powerhead to the tank for flow? Or you will need to increase the size of pump yo are using.
 
Gorillastomp said:
H-Lift max 14.8 Feet
Click to expand...
That means zero flow at 14.8 ft... aka zero flow height. The flow falls off quite rapidly depending on a multitude of factors.

jaypeecee said:
Well, I never knew that! Talk about misleading the customers!
Click to expand...
What can we possibly expect. Manufacturers almost always spec performance under best possible conditions - and we mostly expect them to do so... If a car manufacturer spec 0-100 kph in 5 seconds there is no way we would be surprised if that don't hold up on a 15 degree incline with a full passenger and trunk load.

Cheers,
Michael
 
Nick potts said:
Can you not just add a powerhead to the tank for flow? Or you will need to increase the size of pump yo are using.
Click to expand...
I prefer to have a bigger pump, because using the spray bar, the flow is more laminar. Pump are usually more conical and make more flow interference(Gyre pump are out of this category) I could use Gyre pump but it would cost less to buy a bigger pump for the sump.

Anyways thanks guys for the insight, it was eye opening. I always wanted to test that and never did, wish i did earlier.
 
Maf 2500 said:
The narrower the pipe the more it restricts flow, I wouldn't use 1 inch pipe on a pump with a 2 inch outlet
Click to expand...
Whilst this is "largely" correct, there is a sweet spot for the size of a pipe to optimise flow Bernoulli's principle - Wikipedia

I'm exagerating, and there's obviously a multitude of variables, but sticking a 4" pipe on a 1" pump outlet will not generally speaking improve flow.

On my tank I have an Eheim ecco 200 (quoted 600 ltr/hour and 12mm tubing) and an oase biomaster 250 (quoted 900 ltr/hour and 16mm tubing). The flow on the eheim is much better than the Oase and I think it may perform better with 12mm tubing rather than the 16mm supplied. It wouldn't neccesarily "improve" flow, but might well speed it up. Not sure if that's good or not for a fish tank.
 
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What I'm trying to say.......if you speed up the flow by reducing the size of the outlet, flow rate will be the same(ish) but faster, thus improving circulation around the tank.

Just my hunch.
 
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