DC Pump Output... Pump Curve vs. %Speed

mstgkillr

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After one of my two COR20 return pumps failed, I did a flow comparison with a replacement return pump (Sicce Syncra SDC 7.0) on my Red Sea S-1000. Unfortunately, I do not have flow sensors, so most of the measurements/comparisons are using a 100% open return drain valve. Also, these comparisons are using dual return pumps with one COR20 and one SDC 7.0.

I was interested to note the following:
1. The COR20 did not output any additional flow past 50%
2. The SDC 7.0 continued to incrementally increase flow all of the way to 100%. It appears that it handles the minor/major piping losses better.
3. With the COR20 anywhere between 50% and 100%, and the SDC 7.0 at 50%, the return drain valve needed to be opened 100% and maintained a perfect level in the overflow, which is maxing out the overflow.
4. The COR20 at 50% and the SDC 7.0 at 40%, with the return drain opened 100% maintained a perfect level in the overflow. Again, maxing out the overflow.

I was a little confused seeing the COR20s max output at 50% and not increase even at 100%. I assume it's due to the S-1000 dual 3/4 return piping restriction.

The SDC 7.0 is LOUD... any idea how dual Varios-4 pumps might perform? I'm wondering if the 3/4" piping is choking out the larger pumps and if a smaller pump would perform similar.
 

benbalter

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Do you have a neptune apex? You ezyly add a flow sender to it. Then you see 5he real flow rate. Yes it can be done for about 15$. You may be mixing up flow rate and head presser
 

JNalley

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After one of my two COR20 return pumps failed, I did a flow comparison with a replacement return pump (Sicce Syncra SDC 7.0) on my Red Sea S-1000. Unfortunately, I do not have flow sensors, so most of the measurements/comparisons are using a 100% open return drain valve. Also, these comparisons are using dual return pumps with one COR20 and one SDC 7.0.

I was interested to note the following:
1. The COR20 did not output any additional flow past 50%
2. The SDC 7.0 continued to incrementally increase flow all of the way to 100%. It appears that it handles the minor/major piping losses better.
3. With the COR20 anywhere between 50% and 100%, and the SDC 7.0 at 50%, the return drain valve needed to be opened 100% and maintained a perfect level in the overflow, which is maxing out the overflow.
4. The COR20 at 50% and the SDC 7.0 at 40%, with the return drain opened 100% maintained a perfect level in the overflow. Again, maxing out the overflow.

I was a little confused seeing the COR20s max output at 50% and not increase even at 100%. I assume it's due to the S-1000 dual 3/4 return piping restriction.

The SDC 7.0 is LOUD... any idea how dual Varios-4 pumps might perform? I'm wondering if the 3/4" piping is choking out the larger pumps and if a smaller pump would perform similar.
I have an SDC 6.0 and it's dead quiet at 100%... Are you sure something isn't wrong? Don't get me wrong, I got on Sicce about the XStream SDC's being loud when I first got them, so they're capable of making loud pumps in a market where silent is better, but the SDC's eventually got to a state of silent after about 3 months of break in...
 

benbalter

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I have an SDC 6.0 and it's dead quiet at 100%... Are you sure something isn't wrong? Don't get me wrong, I got on Sicce about the XStream SDC's being loud when I first got them, so they're capable of making loud pumps in a market where silent is better, but the SDC's eventually got to a state of silent after about 3 months of break in...
Well I run jebao pumps my self. Dirt cheap and very quiet. Pumps do have a max flow rate. When they rate pumps they are measured in the best possible conditions. No head pressure no turns and no lift. So then we install them with a flow meter people go "oh the meter is causing a big flow loss ". No we live in the real world lifting water up 2 to 6 feet up and with turns. So i would say get a flow meter and see what's really going on
 

JNalley

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Well I run jebao pumps my self. Dirt cheap and very quiet. Pumps do have a max flow rate. When they rate pumps they are measured in the best possible conditions. No head pressure no turns and no lift. So then we install them with a flow meter people go "oh the meter is causing a big flow loss ". No we live in the real world lifting water up 2 to 6 feet up and with turns. So i would say get a flow meter and see what's really going on
Huh? I'm not understanding what any of that had to do with my post saying OP may have a faulty pump if they're saying it's loud... It's a DC pump and only 1 size up from mine... It should be dead quiet...
 

benbalter

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Huh? I'm not understanding what any of that had to do with my post saying OP may have a faulty pump if they're saying it's loud... It's a DC pump and only 1 size up from mine... It should be dead quiet...
Sorry yes sounds like you have a bad pump
 

DCR

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Noisy pump issues aside, as an engineer familiar with sizing piping, I can tell you that your 3/4" piping is going to severely limit your flow. I would not expect much more than 250-300 gph from any aquarium pump through a 3/4" return line, regardless of the rated flow of the pump (zero head). You could probably get equal performance from a pump rated for 600-800 gph at zero head. The only advantage of an oversized DC pump is that you may be able to run it at a lower speed for noise reduction.
 
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mstgkillr

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Noisy pump issues aside, as an engineer familiar with sizing piping, I can tell you that your 3/4" piping is going to severely limit your flow. I would not expect much more than 250-300 gph from any aquarium pump through a 3/4" return line, regardless of the rated flow of the pump (zero head). You could probably get equal performance from a pump rated for 600-800 gph at zero head. The only advantage of an oversized DC pump is that you may be able to run it at a lower speed for noise reduction.

It has been a while since I calculated major/minor loses in fluids. I appreciate the reply, but how confident are you in that statement? Are you saying that a VariouS-4 (1050 GPH and max head at 14.7 ft) would perform the same as a Syncra 7.0 (1900 GPH and max head at 16.5 ft) with 3/4 piping?
 
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DCR

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It has been a while since I calculated major/minor loses in fluids. I appreciate the reply, but how confident are you in that statement? Are you saying that a VariouS-4 (1050 GPH and max head at 14.7 ft) would perform the same as a Syncra 7.0 (1900 GPH and max head at 16.5 ft) with 3/4 piping?
The Syncra generates 16 ft of head at 300 gph while the Varios 4.0 is only about 8 ft so you will get some additional flow, but it will come at a price in noise and power consumption. The friction losses in 3/4" piping increase significantly as you go over 250-300 gph. I am just saying that you will be wasting a lot of power to try to get much more than 300-gph by increasing the pump size with the 1900 gph pump. If you want more flow than 250-300 gph, it would be far better to increase your pipe size.
 
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mstgkillr

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The Syncra generates 16 ft of head at 300 gph while the Varios 4.0 is only about 8 ft so you will get some additional flow, but it will come at a price in noise and power consumption. The friction losses in 3/4" piping increase significantly as you go over 250-300 gph. I am just saying that you will be wasting a lot of power to try to get much more than 300-gph by increasing the pump size with the 1900 gph pump. If you want more flow than 250-300 gph, it would be far better to increase your pipe size.

I'm currently running dual Syncra SDC 7.0 pumps at 58% with the main drain of my Red Sea S-1000 opened 100%. Just wondering if dual Varios 4 pumps could produce the same flow (maybe even at a higher run percent). It would be much easier if I had real pump curves to review.
 

NancyFish

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The Syncra generates 16 ft of head at 300 gph while the Varios 4.0 is only about 8 ft so you will get some additional flow, but it will come at a price in noise and power consumption. The friction losses in 3/4" piping increase significantly as you go over 250-300 gph. I am just saying that you will be wasting a lot of power to try to get much more than 300-gph by increasing the pump size with the 1900 gph pump. If you want more flow than 250-300 gph, it would be far better to increase your pipe size.
I’m looking at a 1200 overflow into a max 900 reefmat, the overflow is 3/4” drains .. are you saying if I matched the return line (heard they’re supposed to be same or smaller) it won’t be anywhere near that in return because of the pipe?
 

DCR

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I’m looking at a 1200 overflow into a max 900 reefmat, the overflow is 3/4” drains .. are you saying if I matched the return line (heard they’re supposed to be same or smaller) it won’t be anywhere near that in return because of the pipe?
Yes, that is what I am saying. I would say you will not get anywhere near 900-1200 gph through a single 3/4" drain or return line. Your set-up should work fine, but I would not expect much more than 250-300 gph through a 3/4" line. I would run a 3/4" return for your return for a 3/4" drain. You definitely do not want a larger return line than your drains, but equal size should be fine.

I do not believe the ratings on these overflows - at least on a practical basis. To put it in perspective, 1200 gph will fill up a 5 gallon bucket in 15 seconds. Try to imagine that much flow coming out of a 3/4" PVC pipe. The turbulence would be incredible and would likely wash over your rim if it was anywhere near the surface, and you would almost certainly be running full siphon on your secondary or emergency overflow.

I think most reefers over-estimate how much return flow they are actually getting because the friction losses are much greater than they think. I see it in threads where they actually put flow meters in the lines and are surprised by the results - and then question their pump performance. It still all works because I don't think you really need the 5-10X per hour return rates that are commonly stated.
 

NancyFish

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Yes, that is what I am saying. I would say you will not get anywhere near 900-1200 gph through a single 3/4" drain or return line. Your set-up should work fine, but I would not expect much more than 250-300 gph through a 3/4" line. I would run a 3/4" return for your return for a 3/4" drain. You definitely do not want a larger return line than your drains, but equal size should be fine.

I do not believe the ratings on these overflows - at least on a practical basis. To put it in perspective, 1200 gph will fill up a 5 gallon bucket in 15 seconds. Try to imagine that much flow coming out of a 3/4" PVC pipe. The turbulence would be incredible and would likely wash over your rim if it was anywhere near the surface, and you would almost certainly be running full siphon on your secondary or emergency overflow.

I think most reefers over-estimate how much return flow they are actually getting because the friction losses are much greater than they think. I see it in threads where they actually put flow meters in the lines and are surprised by the results - and then question their pump performance. It still all works because I don't think you really need the 5-10X per hour return rates that are commonly stated.
Ugh they make it so confusing, thank you for helping talk about it. Knowing all of that. If I got the 1200 overflow, 3 drain system for my 65g tank, draining into an 900max reefmat roller, and a dc pump that’s 800-1900. Should I run to return lines maybe? Or just the one and not think much other than matching the drain holes?
 

DCR

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Ugh they make it so confusing, thank you for helping talk about it. Knowing all of that. If I got the 1200 overflow, 3 drain system for my 65g tank, draining into an 900max reefmat roller, and a dc pump that’s 800-1900. Should I run to return lines maybe? Or just the one and not think much other than matching the drain holes?
I think a single 3/4" would be OK for a 3 ft 65-gallon, but running two 3/4" lines will not hurt anything. If it is a 4 ft tank, then I could see running two 3/4" lines for distribution although it is not really necessary. You could also just increase the return line size to 1" if you really want to maximize the flow. You just need to be careful that you do not overload your drain system and roller mat and set the return flow accordingly. I would include a globe valve in the return line even if you are going DC just to give some extra adjustment capability if needed. I don't know much about ReefMat and how they handle excessive flow. I assume the secondary and emergency drains would always by-pass it. I suspect that the intended flow rate of yours is probably about 250 gph just looking at the specs. I don't think you would ever want to run it anywhere near 900 gph with a 3.2 in wide roller

If you are really interested in increasing your flow rate, you should at least expand up to 1" right at the overflow bulkhead. I am assuming you have a ReefMat 250 which appears to have a 1" inlet connection anyway so you will have to do it somewhere and you might as well minimize the 3/4".

I don't mean to alarm you. I think your set-up will work fine. I think that 300 gph turnover is plenty for a 65-gallon tank and higher flow rates are likely to increase the roller replacements. I would invest in more powerhead capacity rather than turnover. You probably don't need an 1800 gph pump but you can throttle it down. Worst case you will end up exceeding the capacity of your full siphon drain and have to use more of the secondary overflow. If that happens it could be noisy, especially if the secondary is occasionally going into full siphon mode. If it goes full siphon, you will know it by the noise and just need to throttle or turn down your return pump.
 

NancyFish

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I think a single 3/4" would be OK for a 3 ft 65-gallon, but running two 3/4" lines will not hurt anything. If it is a 4 ft tank, then I could see running two 3/4" lines for distribution although it is not really necessary. You could also just increase the return line size to 1" if you really want to maximize the flow. You just need to be careful that you do not overload your drain system and roller mat and set the return flow accordingly. I would include a globe valve in the return line even if you are going DC just to give some extra adjustment capability if needed. I don't know much about ReefMat and how they handle excessive flow. I assume the secondary and emergency drains would always by-pass it. I suspect that the intended flow rate of yours is probably about 250 gph just looking at the specs. I don't think you would ever want to run it anywhere near 900 gph with a 3.2 in wide roller

If you are really interested in increasing your flow rate, you should at least expand up to 1" right at the overflow bulkhead. I am assuming you have a ReefMat 250 which appears to have a 1" inlet connection anyway so you will have to do it somewhere and you might as well minimize the 3/4".

I don't mean to alarm you. I think your set-up will work fine. I think that 300 gph turnover is plenty for a 65-gallon tank and higher flow rates are likely to increase the roller replacements. I would invest in more powerhead capacity rather than turnover. You probably don't need an 1800 gph pump but you can throttle it down. Worst case you will end up exceeding the capacity of your full siphon drain and have to use more of the secondary overflow. If that happens it could be noisy, especially if the secondary is occasionally going into full siphon mode. If it goes full siphon, you will know it by the noise and just need to throttle or turn down your return pump.
To be honest, this is all new. Just reading tons of forums, occasionally comments (which you’ve been most helpful). And using chat gpt to try and figure out, it’s tough when some say 3-4x and others are like 15x turn over. The fact you’re reassuraning that anywhere near 1200 is overkill is a relief but makes me think my pump needs a switch (unless they’re also inaccurate).

I have the reefmat, I think it’s a 1” connector and so is the two fixed drain pipes in my sump. I ordered the pump because the 800-1900 was the same price as a 450-1450(ish) one (there was a 350-800ish one for like $100 less and I assumed that would be totally inadequate). I thought the more would be better esp if it isn’t accurate with gravity.

It just never occurred to me that when they say 1200+, when it’s set up to mainly drain out of one pipe, doesn’t actually mean that. I didn’t plan to completely max it out but it was a nice thought to have. Just feeling lost on maybe going a different route.

Would it be bad to do a 3/4 to 1” connection for a 1” drain pipe? Or I can just go with a eshopps which I think also use it, modular marine just has a lower profile and doesn’t use the drop down box like eshopps.
 

DCR

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I would keep your Modular Marine 1200 with the 3/4" bulkheads over an Eshopps. It is a much better overflow even with the 3/4" bulkheads. Just install 3/4 x 1" reducers right at the bulkheads and run 1" drain pipe. I would only run the full siphon into the ReefMat and have the secondary and emergency overflows go directly into the sump. I generally say that 1" pipe can reasonably carry 600 gph although the 3/4" bulkhead will reduce that value somewhat.

If you already have the 800-1800 gph pump I would use it. The only real benefit to downsizing would be to save some electrical costs and maybe keep your tank a little cooler. I don't know what pump you actually have but keep in mind that those flow ratings are for zero head and the 1800 rating is at full speed. At part speed and considering the elevation and friction head losses it may be a pretty good match for your system.

I would not fret over the turnover. All of those recommendations are dubious if only because almost nobody actually measures it. Most people are just parroting what they have heard elsewhere. I have never read or heard of anyone improving their coral/fish health by increasing the turnover rate. Many people report successful tanks with 3X turnover. The internal circulation flow and surface agitation is far more important.
 

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