Return pump and head height

[Fishhands]

I was wondering if it was better to have a return pump with higher flow rate and lower max height or a lower flow rate and higher max head hight? I need to pump up only 4ft on a 40g with a 31g sump.

 

[EriksOasis]

You want both high head height and flow rate due to that fact you will lose some flow rat because of the head height. I have always tried to get a pump a lot larger than I needed to get the most recirculation as possible.

 

[Fishhands]

Well for example, I was looking at the sicce 3.0 (714 gph with max head of 9.9 ft) and the 3.5 (660 gph with max head of 12.5 ft). With the 3.0 pumping up 4ft silicone tube im looking at +-428gph. With the 3.5 pumping that high im looking at +-561gph.
I forgot where i got the math from but i think it was at half the head its half the flow without fittings. So total volume of 71g without sand and rocks thats 6x and 8x turnover. I was wondering more if running higher or lower head pressure made a difference other than turnover rate.

 

[EriksOasis]

Yeah the less flow but greater head height equals out to more flow rate total I believe.

 

[theMeat]

When it comes to return pumps bigger is not better. The old thinking was the sweet spot was 10 times the display tank volume per hour. The newer, better thinking is 3-6 times. Ime the bigger the tank the closer to 3x, and the smaller the closer to 6 times. For your 40 gal would go with an eheim 1250 which would give you a little under 200 gph with your 4 feet. Or eheim 1060 which will give you around 350, which is a little hi but still exceptable.

Another thing is, the bigger the pump the more heat it will generate. The quality and design of the pump is also a factor. There’s other quality pumps out there, but you can’t go wrong with an eheim

With 4 feet of head, max head height is not a concern if you buy a decent pump big enough and figure in loss. Can’t think of any decent pumps in the gph range you should be looking at that don’t max out at 10-12 feet, so you’re well with in range where that need not be a concern

 

[EriksOasis]

Good advice.

 

[Fishhands]

Why would the triton method say 10x system volume if thats the "old" thinking? I know that the power heads in the tank create display turnover, but system turnover is what im curious about. I dont plan on running that system however there must be something more than madness to the method of 10x.

 

[theMeat]

Flow rate in tank is important. The flow rate in tank should be 15-25 times the display volume per hour, depending on what livestock you have, rockwork, etc.
The return pump’s gph should be s part of this figure.

Separate from display ‘s flow, the sump to display tank flow....
10x the display’s volume can and will work. 3-6x will generate less heat, and work better, especially for a tank designed around a refugium, because the slower flow will give macro more time with water to uptake nutrients.

Also because it’s good to have a skimmer that can process as much as your return pump is bringing back to sump. Although water changes, bio pellets, algae turf scrubber, or running a methods like triton to control nutrient levels could work too.

 

[McArcher]

You need to decide on a flow rate before you can even know how much head you are dealing with. Vertical height is only one part of head loss. System losses from pipe friction and fittings are both related to the velocity in the system. You have to know the flow before you know the velocity.
In your case, if the vertical distance is 4 feet, you probably have an additional 2-3 feet of system losses depending on fittings and pipe size.

 

[theMeat]

Flow loss and pipe friction are way over exaggerated. As demonstrated by BRS testing that on video. Unless you’re close to max head, or have an unusual amount of elbows, not much of a factor.
On a drain pipe, where gravity alone has to organize the water, a different story.

 

[McArcher]

Flow loss and pipe friction are way over exaggerated. As demonstrated by BRS testing that on video. Unless you’re close to max head, or have an unusual amount of elbows, not much of a factor.
On a drain pipe, where gravity alone has to organize the water, a different story.

That BRS video was comparing head loss between two different types of elbows using 1" pipe. The conclusion was that there was not a significant difference between using 1-90 degree fitting vs. 2-45 degree fittings. The minimal head loss they encountered in the lower flow pumps (coincidentally Sicce 3.0 & 3.5) was due to the low flow (thus low velocity) in the pipe. The results from the tests of the higher flow pumps proves that the pipe and fittings can create a large head loss if the flow velocity is high. It is unlikely that the OP will be using 1" return piping on a tank of that size. In the more likely scenario of him using 3/4" (or maybe even 1/2") piping, the pipe losses can be significant and in some cases even greater than the static (elevation difference) head. Even if he does use 1" return piping, there will be at least 1 additional foot of head loss in the piping which would reduce the flow by 150 gph if he uses the Sicce 3.0. Anyway, my original point was that you need to consider the whole system and not just the vertical height difference when you are picking your pump.

 

[theMeat]

Yep, with the pumps they compared being bigger than what op needs, a smaller pipe would be comparable. Plus a bigger pipe is not always better, depending on the pump and the rise, because it adds more weight/water onto head. But that’s a whole other reef myth.
Just sharing my 30+ years in the hobby, and longer with plumbing. Take it or leave it

 

[EriksOasis]

Just get a pump with a good flow rate and meets your head height needs and go with it. Seems to be a lot of overthinking with the flow rate head height and elbows and fittings. Like I said I always go with more than what I think I’ll need just to be safe most pumps have ability to control and lower flownif needed.

 

[theMeat]

Good advice

All pump manufacturers exaggerate their pumps output anyway. While I find eheim is pretty accurate

 

[EriksOasis]

Yeah no real way to tell other than a flow sensor. But just seems like with all the new technology in the hobby people tend to overthink a lot of things.