Let's get back to basics for a second

[Leadfootedracer]

Can someone explain to me the PROPER way to choose a return pump?

The pump I chose, seems to be underpowered, yet some people said it was too much pump.

I have a standard AGA 90 (48x18x24) with dual returns. I have them tee'd off a single pump. The pump I chose is a mag-12.

I run this pump wide open, and still use 4 powerheads, connected to a wave maker to get adequate flow in the display.

I also notice very minimal flow thru the sump. Obviously the water is getting from chamber to chamber, but the violent splashing and salt creep mess I see in everyone else's units is not seen here. My macro algae is not thriving as it should, and i lead the lack of flow thru the chamber to blame.

So, long story short, what is the proper formula for choosing a pump size?


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[reefstarter]

I think it depends a lot on how much flow you can get through your skimmer .as a general rule 5-10 times tank volume an hour . 20-30 times tank volume in tank flow . I had around 5000 an hour going through my sump at one point and since dialing that back a lot ( id have to do the math ) thins are much better and I have full control over nutrient export with less sump flow

 

[Leadfootedracer]

Is there any variation due to dual returns?

5x90 = 450gph
10x90 = 900gph

The mag 12 does 880 at 3' head and I'm just a hair higher than that I believe.

20x90 = 1800gph
30x90 = 2700gph

Subtract my 880 from the return, and that leaves you with a remaining 920-1820gph required in power heads.

I am currently running 4380gph in the tank. (2 600gph Koralia power heads, 2 1150gph Koralia power heads, 880gph of return)

The skimmer is not sized properly. I needed a quick cheap one to get started and bought a used SeaClone 100 back when I had 1 fish and a new tank. I will be upgrading this in the coming months.


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[choff]

2 separate calculations. There is flow through your sump and flow in your display.

Sump flow
You have. 90g tank plus your sump volume which you didn't state so I'm going to say 10g for easy math. Most people want 5 to 10x flow their sump to maximize the efficiency of the skimmer. You are also trying to grow algae in your sump so that will impact the amount of flow you will want depending on the type of algae in the fuge. Once you figure out your target number that you want, you find a pump that matches that gph at the given head. So, let's say you wanted 8x turnover that's 800 gph. You state that the mag 12 does 880 at 3' and you are a little higher. Now that's 880 gph in a straight line. Every 90, 45 and T will also impact flow rate with 90s having the biggest impact. There are flow calculators out there, Google one and figure out exactly what you can expect out of your pump. Then subtract a little because pumps don't alway work at the optimal number listed by manufacturers. I'm guessing you are in the low 700 range and that's pretty good for a sump. That's it for sump turnover and figuring out the size pump you need. Sounds like you are spot on with the mag 12.

In tank flow.
20x to 30x is on the low end in Imo. I have SPS and like to be over 100x.

Your tank flow is power head flow X # of power heads + return pump flow. This gives you total flow. Divide that number by total water volume and you have your tank flow turn over #.

 

[Leadfootedracer]

Now, does having the power heads run opposing each other (in a pulsating fashion) lower the flow number? (Meaning, although they aren't always on at the same time, do they still count individually towards the total gph)


The mag 12 has 3 90's and 1 tee, so it is safe to assume a far less flow is expected, like you mentioned. I did not think of that in the formula. I will look into getting real numbers when I'm not at work. I do feel, however, my flow thru the sump (12-14 gallons) is a hair slow. My pump valve is wide open (3/4" PVC) and my drain valve is roughly half closed (1 1/4" PVC Beananimal)



My goal here is this;
During the 2016 calendar year I am looking to switch up to DC pumps. First being the powerheads, then the skimmer, and then finally the return. I just want to make sure I'm doing it right.

I have chosen to replace my 4 Koralia power heads with 2 RW-15's. They flow 3900gph max EACH, but will be set to run in an alternating fashion. This will DOUBLE my current power head output and cut the amount of unsightly units in half.


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[G.T]

My simple formula always works. each return 11/4 drain will return about 650 gph tops reliably. so either drill a larger hole for a bigger fitting or drill another hole

 

[Leadfootedracer]

My simple formula always works. each return 11/4 drain will return about 650 gph tops reliably. so either drill a larger hole for a bigger fitting or drill another hole

The drain with the gate valve is the one on the right in this picture. I adapted both drains to run 1 1/4" PVC. One drain (full siphon) has no valve and the other (tuned drain) has the gate valve half closed. This tells me the drains are draining so efficient, that my pump cannot keep up and needed to be partially closed.

Am I wrong? Does my drain setup infact not flow enough?

 

[freakit]

This doesn't sound right. The full siphon drain is the one that needs the gate valve. I Close the gate valve enough so that the water flowing into the open drain doesn't make noise or dump bubbles into the sump.


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[choff]

You are correct. Your drains have zero impact on your flow. If your pump is wide open and your drains are able to keep up, then there is no impact. If you had to throttle your pump because the drains couldn't keep up, then it impacts flow. Drilling another hole would do nothing to your current set up.

 

[Leadfootedracer]

This doesn't sound right. The full siphon drain is the one that needs the gate valve. I Close the gate valve enough so that the water flowing into the open drain doesn't make noise or dump bubbles into the sump.


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Yes, your right. I wrote it backwards. That's how I have the drain setup, and the gate valve is half way closed. It runs mint. Only thing I dislike about it, is the lack of flow thru the fuge chamber.

 

[JohnK]

A 1" siphon drain should flow around 1500 gph. I suspect that drain is not in fact operating as a siphon. If you are running a siphon, you should always have a dry or almost dry back up or else you have a major flood risk. One drain under full siphon and a second drain that's restricted is very risky.

For mag pumps, to get the rated flow you need to use 1.5" plumbing for the return. Running 1" or 3/4" pipe for the return will work but you lose a LOT of flow due to friction loss. With 3/4" pipe you are probably getting way less flow than you might expect.

 

[Leadfootedracer]

I do have an emergency drain, or "dry backup" as you called it. It is 1".

The 3/4" choice was due to the threads on the pump being 3/4". Your only as fast as your smallest restriction, so I just kept it all the same.


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[Roccus]

I'll add a couple of things here...head pressure is greatly mis understood...when ordering a pump.. look at the pump performance curve... some pumps drop off dramatically as the head pressure rises.. some so badly as to have 0 flow at their max point.. always look at the performance curve... also ... most unions you get at the big box stores have opening much smaller than their rated ID .. for instance a 3/4 union may have an ID of 1/2"... I've found in critical application if I cant buy a Hayward or other brand name SCH 80 union , I go up 1 size and use a reducer busing ( either thread or slip) to get the ID I desire.. it may seem like a small thing but when you cut it close on max flow.. every little bit counts....

 

[IPWitan]

This is a very good question and unfortunately one where I have not seen any literature. None has been sited, but that isn't exactly rare in this field. In theory, it would seem that you want to send enough water into the sump such that it can be filtered, whether by skimmer or refugium. As for your skimmer, it is very low end (about $100) and likely nothing like what the other posters have in their sumps. I am a cheap bastard but use a $300 AquaMaxx Cone. The SC uses a 1200 maxijet, and mine uses a Sicce rated at around 1800, I believe. Either way, both will put the water in the chamber at least 2x before it moves on to the next chamber. Is that enough, who knows...

Onto your refugium...Plant filtration is incredibly efficient, however, you do not want the water to be flying past the plants so fast that there is no uptake. Notwithstanding, I haven't read a study about optimal flow. The beauty of biological filtration is that it will increase and decrease rapidly based on supply. If you have high nutrients and good light, it will grow to balance. Consumption will equal supply. I suppose it is possible to have a very nutrient rich tank and a large refugium such that you cannot supply enough water to maximize the potential of the bio cleaning, but that seems unlikely.

Personally, I have a Mag 5 in a 30 gal sump on a 75 gal display. My research suggested this was enough. I use flexible tubing on the return - not pvc. For me, the issue is noise. I do not want there to be noise from the drain or when the water moves from chamber to chamber. A big pump also means more noise, more heat, and more watts. So in my mind, there is some good reasons to not go crazy with massive flow in your sump.

So in the end, it is hard to imagine that a Mag 12 would be too low a flow. Countless numbers of people use far less and get great growth in a refugium. http://reefcentral.com/forums/showthread.php?s=&threadid=216369. Moreover, if there is a problem, I highly doubt this is it. Notwithstanding, there are many other opinions that are better than mind.

DAG

 

[JohnK]

I do have an emergency drain, or "dry backup" as you called it. It is 1".

The 3/4" choice was due to the threads on the pump being 3/4". Your only as fast as your smallest restriction, so I just kept it all the same.


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Right, I posted on a 4 am bathroom break, missed the posts clarifying.

Anyway, don't miss that Danner rates those pumps using 1.5" pipe. As Roccus mentioned, some pumps don't handle head pressure well, Danner is the poster child for this. While the threads on the pump are only 3/4", the "friction loss" in 3/4" pipe kills the flow on those pumps. I get the logic, but in this case "your only as fast as your smallest restriction" doesn't apply very well. Go up on that return pump diameter and you should see a substantial gain in flow.

 

[Leadfootedracer]

So basically, if I increase the pipe diameter on the return, I will see more flow, and possibly be happier? I can dig that. Do I need to go beyond the tee? Or will larger tubing up to the tee suffice?


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[JohnK]

So basically, if I increase the pipe diameter on the return, I will see more flow, and possibly be happier? I can dig that. Do I need to go beyond the tee? Or will larger tubing up to the tee suffice?


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Pretty much yes. If you can go up on the t you should see the best gain, but if you can't you should still see at least some gain. I can't promise that the improvement will truely be night and day, but it should make a difference and get you into the ballpark of what's claimed for those pumps.

Check the PDF on this link with instructions for the mag12. On the second page it states that you should have a minimum of 1.5" ID on the tube/pipe.

http://www.dannermfg.com/Store/Products/Danner/PID-02712.aspx

 

[Leadfootedracer]

Ok. The tee is 3/4" barb for hose and it is 2 hoses up to the tank. So the run of 3/4" PVC is only about 2'. I will look into it, as a DC return pump is the last thing on my list.


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[JohnK]

I will look into it, as a DC return pump is the last thing on my list.

Don't worry, the Chinese DC pumps that are all the rave these days aren't much better with head loss than the mag pumps

 

[Leadfootedracer]

My pump isn't loud, and I don't notice any heat issues, i just wanted to swap it out for something with more power, and the DC pumps are all the rave like you said. If upping the size of the plumbing gets me more flow, it will stay.


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