1" plumbing for Mag 9?

[ErikS]

Anybody know why the manufacturer of mag drives doesn't just size the outlet appropriately, or at least include a bushing with the unit?

Because they're a cheap pump, there's nothing "quality" about them. Sloppy impellars, cheap magnets = hot, inefficient, and weak. Classic case of you get what you pay for.

It's not headloss so much as ratings. The performance curve put out by Danner is inaccurate - the pump can't deliver near what they state. They rate the pump @ 0' with at least twice the output size.

Marketing - say a pump moves X gallons for Y $ = a value.

 

[TheDrunkenClam]

Not sure about the ratings from Danner but the RC calculator is spot on. I just finished testing my DIY sump with a Mag 5 return using 3/4" return piping (mostly hard PVC, short section of Vinyl), 2 45 degree elbows. one 90 degree, a Loc-line return nozzle, and 4.5 feet of head.

Based on my tests with freshwater, the flow rate was just under 300 gph, right where the calculator predicted.

I agree that it is a cheap pump, but it does the job (at least in my sample of one). I went with the Mag because this is my first sump and if I decide to make changes to flow rates or design, I can toss the Mag without feeling like I am out big money.

 

[horkn]

doubling the size of the plumbing doesnt work out when you figure the volumetrics.

a 1.5" pipe will flow a lot more than 2x what a 3/4" pipe will.
let me get out my plumbing book and i will give you the hard numbers

 

[clsanchez77]

horkn

I do not recall anyone here suggesting that doubling the pipe size will double the flow. We have already beaten pipe flow dynamics to death here:hammer:

The issue is the pump curve on the Danner pumps looses a lot of flow with little initial head, that is the pump curve is steep compared to other pumps in the hobby.

In order to get similar flows to similar pumps availble in the hobby, you need larger pipe than what would be used with other pipes; this is why danner recommends doubling the size of the pipe to their fittings, where as with eheim and others, this is not necessary.

But from what I recall the magic number is either 6 or 8 times capacity for doubling the pipe diameter, its a function of hydraulic radius.

 

[sjm817]

<a href=showthread.php?s=&postid=6574817#post6574817 target=_blank>Originally posted</a> by TheDrunkenClam
Not sure about the ratings from Danner but the RC calculator is spot on.

The RC calc also shows a Mag7 outflowing an Eheim 1060 (same as 1260) running the same size plumbing and head. In reality, the opposite is true. The Eheim significantly outflows the Mag7. It also shows a Mag9.5 only having a difference of ~ 100GPH between 3/4" and 1.5" plumbing @ 4'. It is a lot more than that. It may be accurate in some cases, way off in others.

BTW, I ran your numbers, and it came up with ~ 250 GPH. Sounds about right for a Mag5.

 

[clsanchez77]

Just looked into it...Doubling the diameter of your pipe will factor your flow capacity by approx 4...that is if you have a flowrate or 440gph in 1" pipe with a headloss of 5', you can get 1,760gph in 2" pipe with the same headloss of 5'.

That only provides a rough estimate as it neglects changes in turbulent loss factors which are dependent on pipe diamter, but it gernerally works pretty well.

 

[sjm817]

<a href=showthread.php?s=&postid=6577901#post6577901 target=_blank>Originally posted</a> by clsanchez77
Just looked into it...Doubling the diameter of your pipe will factor your flow capacity by approx 4...that is if you have a flowrate or 440gph in 1" pipe with a headloss of 5', you can get 1,760gph in 2" pipe with the same headloss of 5'.

That only provides a rough estimate as it neglects changes in turbulent loss factors which are dependent on pipe diamter, but it gernerally works pretty well.

The type of pump makes a difference too. With flow pumps like Mags it really makes a big difference. Pressure pumps, not nearly as much.

 

[clsanchez77]

That is the 'steepness' of the pump curve. If someone got the pump/flow data for a Mag and an Eheim and plotted them together, they just may both start at the same points ('0 head' which is where the manufacture rate them), but the Mag will hit the ground (no flow) first.

Also, still playing with the numbers out of my book...if you hold your flow constant, and double the pipe diameter, your headloss is reduced by a factor of 16! Of course then the pump pushes more flow, increasing the headloss again, so it does not really work that way, but stepping through the iterations you can defintely see it.

 

[horkn]

<a href=showthread.php?s=&postid=6577743#post6577743 target=_blank>Originally posted</a> by clsanchez77
horkn

I do not recall anyone here suggesting that doubling the pipe size will double the flow. We have already beaten pipe flow dynamics to death here:hammer:

The issue is the pump curve on the Danner pumps looses a lot of flow with little initial head, that is the pump curve is steep compared to other pumps in the hobby.

In order to get similar flows to similar pumps availble in the hobby, you need larger pipe than what would be used with other pipes; this is why danner recommends doubling the size of the pipe to their fittings, where as with eheim and others, this is not necessary.

But from what I recall the magic number is either 6 or 8 times capacity for doubling the pipe diameter, its a function of hydraulic radius.

i know, but it really hasnt been dealt with accordingly. thats shy i mentioned that

i do think its like something like the 6 or 8 times capacity for doubling the pipe diameter though...

so, i got a sweet deal on a new mag 9.5

if i run it as my sump return pump (like 4 foot of head maybe) witha scwd, do you guys think it will be too much for my 35g?

i have a 200 gph ph, a 300 gph ph, and a 250 gph of canister filter at the moment, and i would like to eliminate all of the ph's and only use the canister for water polishing and carbon/ phosban in my sump when i get that going...

and i am assuming i should run 1" tubing on it up to the scwd instead of the 3/4 " they recommend

 

[sjm817]

I ran a 9.5 with a SCWD as a return. It cut the flow to very close to that of a Mag5. I ran it both with 1" and 3/4" on the input side. I ran 3/4" on the outputs but never tried 1" there. 1" did make a small, but definitely noticeable difference on the input side.

How big a sump are you going to use? Be aware that you are adding 93W of heat to the setup.

 

[clsanchez77]

I think you will be fine with that setup, where did you get the Mag 9, I am debating between the Mag 7 and Mag 9 and I am not looking for high flow through the sump, 4' head also 1" pipe.

Figure the SQWD will reduce the flow about 35% so figure your flow without and deduct, it should get you ballpark.

I am guessing 400 on the Mag 7 and 500 on the Mag 9. Since I will have a Mag 7 on the skimmer and a Mag 7 on the chiller, I figure keep it simple.

 

[clsanchez77]

It does not all go to heat, but they are pretty inefficent pumps. Guess it is sort of ironic that I am planning to use one to drive the chiller...oh well.

 

[horkn]

a local reefer/ motorcylist is selling me the 9.5 for 25 dollars, its new.

i am thinking of making the sump out of my 20L I have, but i know its not that tall. so i may buy a 15 or 20High...

93 watts is still less than all the other pumps i use combined....

thanks for the help guys

 

[sjm817]

20L is a nice sump. I'd rather have the 30" length over the 24" of the 20H.

 

[horkn]

that and its already paid for

i bought it new a few years ago for a baby gar i caught on the missisippi river (with my bare hands crocodile hunter style)
and i never added any chemicals to that tank.

i only had the tank up for a year, since the gar quickly outgrew the 20L, and i released it into the river again....

 

[sjm817]

If the 20L will fit in the stand or whatever, I'd put some baffles in it and use it.

 

[horkn]

yeah, i think it will barely fit in the stand. the tank is only a 35g 3 foot x 12 deep....