Head Loss ???

[raymond4133]

http://www.reefcentral.com/calc/hlc2.php?submitted=1&VerticalLength=4&HorizontalLength=2&PipeDiameter=0.75&PumpID=1&Elbows90=4&Elbows45=2&GateValves=0&BallValves=1&Couplings=0&CheckValves=0&Exits=2&Entrances=1

Just curious...I was testing out the head loss calculator here on RC...and well I'am still debating between Two Quiet One 4000 pumps or one MAG 18 pump...Now I prefer to get the two Quiet One pumps but it seems that a lot of people say they are unreliable since they always have problems restarting...Then again the MAG pumps are said to make lots of noise and have heat issues...

Well anyways I put in the feet lengths and elbow numbers etc. into the calculator and I just wanted to clarify how would I determine each of these...

Somehow I think I'am doing this calculator wrong...If I get one Mag 18 pump and split them with T splitter would that be considered two elbows? Then when calculating the horizontal and vertical feet do I multiply the amount of feet of one of my return pumps by two for two returns...

So for example one of my overflows has 4 ft. in vertical height so does that mean for both overflows I will have 8 ft. in vertical height or is still 4 ft.? (THIS IS MY MAIN CONCERN)

 

[Sparkss]

head height is typically to account for gravity, so you should only need to calculate it once in your setup.

HTH

Anyone else can chime in to correct me

 

[raymond4133]

I always thought that head height would need to be calculated by how much total height do I have in the system ... So that is why I thought it would be 8 feet instead of 4...

But hopefully we can get more help on this...

 

[Reefugee]

Tom,

It is possible that you are correct, but logic says it should be counted as 8ft. I was wondering if you T the return, don't you have twice the volume of water, thus twice the weight of the water counteracting the pump? I would guess that you would have to could headroom as 8ft and not 4 ft.

Like I said - I could be wrong.

Minh

 

[CaliforniaDreamer]

<a href=showthread.php?s=&postid=8535747#post8535747 target=_blank>Originally posted</a> by raymond4133
I always thought that head height would need to be calculated by how much total height do I have in the system ... So that is why I thought it would be 8 feet instead of 4...

But hopefully we can get more help on this...

As it turns out Sparkss is correct, only 4 feet of head due to height above tank. This is because it is not the actual weight of the water (if that was true then a larger pipe would have more head) but due to the pressure difference. Also note that the friction head for the return pipe would be less with two legs, but that loss is usually very small unless you are pushing a very high velocity through the piping.

 

[raymond4133]

Is that principle the same with Horizontal head pressure...I would say I have at least 2 feet on each side...?

And would the T joint that would split the water flow to two overflows would that be considered two elbows or just one...?

 

[CaliforniaDreamer]

<a href=showthread.php?s=&postid=8535953#post8535953 target=_blank>Originally posted</a> by raymond4133
Is that principle the same with Horizontal head pressure...I would say I have at least 2 feet on each side...?

And would the T joint that would split the water flow to two overflows would that be considered two elbows or just one...?

-- EDIT --
To directly answer your question, the T should be counted as a T. I would count the 2 elbows as a single elbow and the 2 foot runs as a single run.

-- END EDIT --

I'm not sure what you mean by "horizontal pressure" but horizontal runs do incur "head" because of friction. I would however assume a single run for the purposes of total head calculation. The "head loss calculator" simplifies the calculations somewhat but it will be close enough. For example once the pipe is split into two pipes you would have to change the calculation to show a pipe of greater diameter of calculate the head in each loop separately. If you do decide to calculate separately then you will run into the problem of the 4 foot head being added twice (which is wrong). Unfortunately the head loss calculator is just not setup to calculate the head for complex pipe runs. If the entire return was made up of two 1 inch pipes for example that would be similar to using a single pipe with twice the volume (approximately a 1 1/2 inch pipe). Using two elbows into two legs of a return that uses the same size of pipe, results in less head.

In any case the numbers you get are going to be approximations. I wouldn't fret too much about getting exact numbers, just try to get close enough that you won't overdrive your overflows or can't get enough flow through your sump.

 

[Reefugee]

I stand corrected. Thanks for the info.

<a href=showthread.php?s=&postid=8535877#post8535877 target=_blank>Originally posted</a> by CaliforniaDreamer
As it turns out Sparkss is correct, only 4 feet of head due to height above tank.

 

[raymond4133]

well according to my calculations Iam now looking at a MAG 12...or 1200gph...

I will get some sort of ball valve to regulate the flow if i need to adjust it down a little...

Would everybody agree that one MAG12 be enough to supply about 600 gph +/- to each overflow return...

I will T them off splitting the flow and I have about 4 feet of height or vertical height...

Thanks everyone for all your considerations...

 

[CaliforniaDreamer]

One other thing I should say is that if the total head is more than a couple of feet more than the head due to the height of the return you are using too small of diameter of pipe. A case where this is not true is if your outputs require pressure such as eductors on the outputs or some kind of flow switching device such as an Oceans Motions director. Even in these cases the extra head should come from the device not the piping. But then these devices really don't belong on a sump return anyway, much better utilized in a closed loop.

 

[CaliforniaDreamer]

<a href=showthread.php?s=&postid=8536420#post8536420 target=_blank>Originally posted</a> by raymond4133
well according to my calculations Iam now looking at a MAG 12...or 1200gph...

I will get some sort of ball valve to regulate the flow if i need to adjust it down a little...

Would everybody agree that one MAG12 be enough to supply about 600 gph +/- to each overflow return...

I will T them off splitting the flow and I have about 4 feet of height or vertical height...

Thanks everyone for all your considerations...

Depends on the size of your returns. A mag 12 with 6 feet of head is about 950 GPH, not 1200 GPH.
Also if you put a ball valve in to help regulate the flow, put it in as tee'd off the return with its output back into the sump. This way is easier on the pump and reduces the electrical load on the pump. Don't put it inline and use it to restrict the flow.

 

[raymond4133]

http://www.reefcentral.com/calc/hlc2.php?submitted=1&VerticalLength=4&HorizontalLength=4&PipeDiameter=0.75&PumpID=2&Elbows90=4&Elbows45=0&GateValves=0&BallValves=1&Couplings=0&CheckValves=0&Exits=2&Entrances=1

Here check out what I put into the reefcental head loss calculator...

If what you said about the vertical head pressure is right than I guess I will be able to 659gph on each overflow return...with 4 feet head instead of 8 feet head on the MAG 12...

-Are you sure it's not 659 gph divided into two...making 330gph going to each overflow return...? It just seems to confusing only having only 4 feet instead of double...

 

[CaliforniaDreamer]

<a href=showthread.php?s=&postid=8536621#post8536621 target=_blank>Originally posted</a> by raymond4133
http://www.reefcentral.com/calc/hlc2.php?submitted=1&VerticalLength=4&HorizontalLength=4&PipeDiameter=0.75&PumpID=2&Elbows90=4&Elbows45=0&GateValves=0&BallValves=1&Couplings=0&CheckValves=0&Exits=2&Entrances=1

Here check out what I put into the reefcental head loss calculator...

If what you said about the vertical head pressure is right than I guess I will be able to 659gph on each overflow return...with 4 feet head instead of 8 feet head on the MAG 12...

-Are you sure it's not 659 gph divided into two...making 330gph going to each overflow return...? It just seems to confusing only having only 4 feet instead of double...

Based on your numbers that is correct. If you use 1 inch pipe you would get 870 GPH or 435 per side. With 1 1/4 inch pipe you would get 1007 gph or 500 gph per side. If at all possible I would go with larger pipe, much easier on the pump and the extra flow is almost free.

 

[dots]

http://www.reefcentral.com/forums/showthread.php?s=&threadid=960296

I think most of the initial questions were answered here, no?

Easy way to think about it.......based on others findings the megaflows will flow a MAX of 600pgh per. So your theoretical max is 1200 gph.

Lets ignore minor losses due to fittings and ONLY consider the major loss due to gravity which is dependent to the diameter of the pipe. Which is vertical rises only, measuring the center of pump outlet to center of the pipe at highest elevation. Since you have two pumps......this will be equal for both on one riser per, or double it for two seperate returns to the two seperate overflows powered by one pump. Provided there isn't more than a couple of fittings, you will be close enough.

Because here is the kicker, even if you find that you need a pump that will put out 1010gph to account for those losses and still have the max flow, that are the odds the brand you want has a pump rated at 1010gph? Odds are usually slim they will have your exact need, so you either will buy the lower flow rated one and call it good, or you will have to buy the larger one. If you buy the larger one, you may have to put a spoiler in it, (tee'd ball valve running back into your sump), so you burn up the motor by adjusting the back pressure.

So put in the calc just your pipe dia, and rise...and call it good. This will give you that ballpark number.....find the size of pump you need and size the next rating bigger(or smaller, where not talking a big difference overall, water still will be filtered but at 8 or 9X rather 10x).....if its within say 10-15%, you probably wouldn't need that spoiler because the minor losses(entrances, exits, fittings, reductions) we ignored & mechanical ineficiency will be take up that extra.

So how bout you pick a brand of pump first based on cost, reliability, ease of maintaince, and prefererence......say about 1200gph or so based on that theoretical max, because it will be less than that....(or see what others with two overflows have) and we will see if your design won't take out that much loss, because its easier to make the plumbing match the pump, rather pump match the plumbing....Were talking just a normal stand correct, your not running pipe 50' from the garage up two flights of stairs, just 4' maybe?......

However, I myself would prefer to have one pump as the return pump so I would really have to worry about getting the max flow at the exit so much, and buy another for a closed loop system another time, use a larger diameter and get more flow out of it with less velocity.

So I guess the main question is, do you want the max flow with a spoiler, or no spoinler and less than max flow?

 

[raymond4133]

Well I was really considering two Quiet One 4000 pumps but Iam so deterred by all the negatives I have heard about them...(Not restarting etc..)

Also I did not really like the idea of having two pumps anymore...So Now Iam considering the MAG 12 that seems to be pretty close to what Iam looking for my specifications...

According to the head calc it looks okay...But what still puzzles me is how can a 1200gph MAG 12 have a maximum of 1200gph at 0 feet and still be able to provide approximately 659gph to each of my overflows...It just does not add up...at this standpoint it looks like 660 gph x2 which would 1320gph at 4 feet vertical head on a 3/4" return pipe...


what do you all think?

 

[dots]

Personally I like the idea of two pumps for a redundantcy system.....and one may want to consider if you have two versus one submersed pump is it possible that the two smaller pumps combined may put less heat into the water than one larger if one were wanting to reduce that, or possibly when stepped up to that level one larger one is so mechanicaly ineficient that the two combined still consume less energy than the mongo one, or vice versa.

As far as the numbers......I don't know, I mentioned before that I don't really trust that calculator for splitting hairs, because I don't know which formulas are used, which flow type is assumed,smoothness of pipe, and other assumptions were made......but it gets us into the ballpark.

Other factors based on a flow rating vs actual performance, how those rating numbers were found and the sample group your run of the mill statistical stuff, could be the source of the difference. But you didn't really calc any of the numbers and can't be 100% if any are the true values........just a ballpark +/- 10% hopefully.

Regardless, it seems you have done your homework and a 12 sounds reasonable.....lets assume it really has less gph and you are correct, what then up to a 13 or 14?......(don't know the sizing).....if then you are probably too high and need the spoiler....but no biggie, easy fix.....do you want to be on the low side or the high side of your max flow is what you need to decide and adjust your design based on that.

 

[raymond4133]

I really don't mind if it is a little under flow then maximizing my sump...I just wanted to replace the two pumps I have in their right now...One of them is a RIO 2500(althouh it has never failed on me for at least a 2 years now...) But it seems a lot of people disgust them and say they will kill everything...And I really don't want that to happen...

So how dependable are MAGs...in this case the MAG 12

 

[Sparkss]

<a href=showthread.php?s=&postid=8536420#post8536420 target=_blank>Originally posted</a> by raymond4133
well according to my calculations Iam now looking at a MAG 12...or 1200gph...

I will get some sort of ball valve to regulate the flow if i need to adjust it down a little...

Would everybody agree that one MAG12 be enough to supply about 600 gph +/- to each overflow return...

I will T them off splitting the flow and I have about 4 feet of height or vertical height...

Thanks everyone for all your considerations...

Well for one thing, a MAG 12 is reported as only having 1130 GPH at 4' head (this from the MAG Drive head/flow table). Factor in that you are not using the optimal size pipe (their flow calculations are typically based on a pipe that is twice the size of the output thread of the pump) and the bends that you have in your return, there is no way that a 12 will push 600 out of each of 2 returns. You are looking more like 400-450 (being generous), give or take, out of each return, with your setup. all depending on how close to the pump you put your T.


EDIT : I jsut saw the post by CaliforniaDreamer that already said all of this.. sorry to have basically copied his post . Look at it as confirmation/agreement with what he posted, but in different words

 

[raymond4133]

I guess iam back to a MAG 18 now...?


:rollface:

 

[Sparkss]

you can probably get 500 - 550 out of each side/return out of that 12, if you use big enough pipe (and 2 4' head.. any higher and the GPH just goes down). Just use a 3/4" X 1 1/4" or 3/4" X 1 1/2" RE on the pump into a similarly sized female fitting.