Pump flow question???

[Maxx]

Okay....this is weird.....
According to the math, my return pump in its present configuration is only putting out 316 GPH. Its a Mag 7 connected to 1/2" plumbing using 3 P traps as opposed to at least 2 90 degree elbows. There is one 1/2" true union ball valve and on 3/4" union adapted to fit. The 3/4" was used in place of a 1/2" union due to flow restrictions.
I used the Skimmer Math link to calculate the return pump flow. If its works for skimmers, it ought to be able to work for smaller return pumps...

Just to be on the safe side I did the math using the example they provided.....came up with 60. Did it again. Same answer.
So I decided that it was necessary to add a zero at the end of the answer. Then went out and got a bucket, and an oversized piece of flexible tubing. The tubing was oversized in order to prevent friction from being a factor. At no time was the hose completely filled with water from the return pipe...just kinda like a water slide...all along the sides and bottom of the tubing. It took 57 seconds to fill the 5 gallon bucket.
5 divided by 57 multiplied by 360 equals 31.5789.....roughly 31.6. Adding a zero gets me 316 gph. This is a mag 7 and I was expecting somewhere in the 400 gph range.
Next I went to the RC head loss calculator and entering in all the info I would have if I were plumbing it with 90 degree elbows.....it came out to 410 gph. BUT the smallest diameter plumbing that it allows to be used in the calculator is 3/4 inch...and I'm running 1/2 inch....so that might make a large difference....
I remember reading on a long forgotten thread that Mag drive pumps require oversize plumbing...but that made no sense to me. Anybody know if this the case?
Any answers or thoughts?
Nick

 

[tommyp]

Nick, I think most pumps benifit from oversize plumbing. when reading about my mak4 it was suggested to put 1" bushings on the 3/4 outlets. I did but never tested it. dunno a bout a mag though

 

[Maxx]

I thought I had spoken to Mojo about using oversized plumbing and he was against it....
I looked again at the box and one sheet of information included along with the pump....nuthin'......
Maybe I should switch to one of the bombs of oceanrunner?

I'm really not wanting too much more flow.....360 to 400 gph were be more than enough. I'm not wanting to have huge volumes of water crashing into my sump...right about 4-5 times total system turnover would be great. I have the closed loop to compensate....

 

[tommyp]

Yeah I am not for gobs of flow through the sump ether. I have no fluid dynamics training so don't have a clue about upsizing the plumbing. I don't think that 1/2 to 3/4 would hurt is there any way to do a test to see if it increases flow before you swap everything out? You might just be seeing normal output of the mag and the manufactures ratings are too optimistically high

I have had the worst luck with oceanrunners. They never start for me once they turn off. regardless of how much I soak them. I have to open the lock on the impeller and start the impeller running than close the impeller cover while it is running to get them to start. I think I am the only one with this problem.

T

 

[mps9506]

Maxx,
I personally have about 450-500 gph of flow through my sump. this is a 30 gallon sump on a 40 gallon display tank. I pretty happy with that. It is pretty quiet, I get more noise from my Euroreef than the water itself(and the euroreef is pretty dang quiet).
I get the rest of my flow from powerheads and hopefully a closed loop pretty soon.
I'm using a mag 9.5 with 3/4 inch plumbing through a 3/4 inch sea swirl. I think about 4.5 feet of return plumbing plus a total of 4 90 degree bends(kind of inevitable with the sea swirl).

Just bump your plumbing up to 3/4 inch all the way from the pump to the return outlet. If you find the flow too much, then just use a quality ball valve to reduce the flow (I stress good ball valve, I've had nothing but lock ups from the home depot valves).

Mike

 

[Maxx]

Well,
I've been able to get a good price on a used Mag 9.5 so I will using that in place of the Mag 7. Running it through RC's calculator, I got 544 GPH. This is using 4 feet of head, five 90 degree elbows, (a T to split the returns and two for each side to go over the wall of the tank.) a True Union ball valve, (I will oversize this to reduce restrictions), and 4 exits via Loc-Line Y's. This should get me a tank turnover rate of approximately 6.8 times an hour...within my target range without being completely violent in my sump.
I will angle the flow to blow down on either side of the overflow where my closed loop returns exit the sides of the box. I want to minimize detritus collecting in the back of the tank in an area will it will be difficult to remove.
Nick

 

[mps9506]

Sounds good to me...
Let us know how it goes.