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Frustrated and need some help


Jay

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Ok heres my problem.

 

I have this needlewheel pump for my skimmer. It was working great for the last 9 months or so then it kind of quit making good bubbles. I took it apart and cleaned the mesh modded impeller and that did not help. I then took it apart and trimmed the mesh thinking that it was rubbing on the housing of the pump. This did not help either. Then I checked the inlet of the pump by putting my finger on it and its barely sucking any water when before it would really slam my finger when I put it near the inlet ( if you know what I meen I hope (scratch) ) So I took it back out and discovered that the airline was comming out of where it was glued in place so I removed the airpline and cleaned up the surface and reglued the air tubeing in place where it was before. This still did not help it so just to test I plugged the airpline and wham....the pump starts pumping water like 2000 gph like it is supposed to so I really dont think the pump is bad and the impeller seems to spin and pump just water like its supposed to. When I unplug the air tube and allow air back in the pump starts cavitating and rattleing some and the water flow is dramatically reduced. It does make bubbles but when I hook it up to the skimmer body its obvous it is not right. sooooo what makes it cavitate and rattle. Can someone fix it? Should I just buy a new pump which I have no problem doing. If I buy a new pump should I do the mesh mod to it? Frustrating...really.

 

Jay

 

Pump is a SL-6530 46 watt 2000 l/h

I think it is a sealine pump as that is what google indicates

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Unless the mesh significantly increased the weight of the impeller i don't see how it would reduce the life of the pump. In contrast, the mesh should be helping pull more air in, which in turn would make the impeller easier for the pump to spin, which would INCREASE the life of the pump IMO.

 

Jay just to clarify. With the airline plugged it runs full bore no problems. Then when you open the airline it cavitates?

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Mesh-modding a pump reduces the overall flow of water through the pump; since most pumps are cooled by the water passing through them, reducing the flow allows the pump to get hotter thereby reducing the life. Whether it's a significant reduction depends on the quality of the pump, phase of the moon, etc.

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In addition to Andy's point about water flow, I would think the mesh mod would also introduce the issue of balancing. Unless the mod were perfectly balanced (or at least as well as the stock impellor), that would add an additional source of stress on the pump and potentially shorten life as well. Again, could be insignificant compared to the benefits...

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Thanks Andy' date=' I knew it was a SIMPLE thing to understand.[/quote']

 

Then why didn't you give any information other than someone told me this? For all we know you got that info at Petco.

 

 

 

 

A pump sitting in water will be cooled by that water. Not just the water being pulled thru it. Besides, the air being pulled is most likely cooler than the water (who keeps their house at 80 degrees?). Having more air in the volute would reduce friction as well as pressure, leaving the impeller to spin more freely and the pump to use less electricity to move the water. This is why you have a significant drop in wattage that the pump pulls when the meshmod is done.

 

My pump went from 80w to 43w. So if the pump is using half the normal wattage, that tells me its running more efficiently. Wouldn't you say 80w creates more heat than 43w?

 

 

 

Mesh-modding a pump reduces the overall flow of water through the pump; since most pumps are cooled by the water passing through them, reducing the flow allows the pump to get hotter thereby reducing the life.

 

So wouldn't this mean that the pumps that pull the most air will have the shortest lifespan?

 

 

 

 

 

But then again this is all so simple....

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Then why didn't you give any information other than someone told me this? For all we know you got that info at Petco.

 

Was that directed at me? Confused...

 

A pump sitting in water will be cooled by that water. Not just the water being pulled thru it. Besides, the air being pulled is most likely cooler than the water.

 

No, most pumps of this type are designed to be cooled by the water passing through them. Water is a much more efficient medium for the transmission of heat than air is. Running a pump dry is bad for it, right? This is one of the main reasons.

 

So wouldn't this mean that the pumps that pull the most air will have the shortest lifespan?

 

If that was the only factor involved, yes. But it isn't, so not necessarily.

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No it wasn't for you.

 

 

External pumps are designed to be cooled by the water passing thru them yes, i would not argue that. But internal pumps i do not agree. The inner workings are protected by the same thin flimsy plastic throughout the pump. Sitting in a volume of water, the surface area in contact with the pump is exponentially greater on the outside versus the inside of the pump. And again, the air passing thru the pump is cooler than the water will ever be. Mixing air that is cooler than the water you are mixing it into would drop the temp of the water right?

 

Running a pump dry is bad because there is nothing to eliminate friction. Friction = heat. Coat the impeller area and volute in grease, run it dry in a temp controlled room and I do not think it would have problems.

 

 

And we haven't even touched the drop in wattage.

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My pump went from 80w to 43w. So if the pump is using half the normal wattage, that tells me its running more efficiently. Wouldn't you say 80w creates more heat than 43w?....

 

Wow... that is pretty impressive Miles! That definitely suggests the back pressure of the water under normal circumstances is creating a greater load then the air/water mix with the mesh mod. Just wondering about your point re lubrication and friction. Do you think there is any increase in the friction and possibly localized heat (at the impellor interface) with the increased air flow? Perhaps there is a trade-off between the reduced load (back pressure) and reduced lubrication?

 

Not trying to start anything here... just trying to understand.

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Not familar with that specific pump, but sounds like the introduction of air is causing an imbalance....check the bushings that align the impeller front and back...does it make a rubbing noise when air in injected?? maybe a section of the impeller is worn and causing the imbalance once less friction is introduced? Once air is allowed in, IMO this allows the impeller to spin more freely as the actual weight its pushing is less.

 

I have a Mag 350 canister and was having similar issues.....keeping air bubbles out.....it ran fine...but once I replaced the impeller...it did much better....no sounds of imbalance...just a worn impeller.

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I'm just discussing as well. I have a hard time just believing something stated without anything to back it up. Its an interesting subject, one we probably can't really come to a conclusion on without some sort of testing equipment.

 

What it tells me is that the increase in air that is pulled allows the impeller to spin more freely. Less resistance due to more air. I pull air from outside, so during a typical 60 degree day i would think the water/air mixture around the impeller would be cooler than the tank water, or at least very close. Cooler air mixed with water cools the water. This alone would do enough to keep the pump at the same temp it would be if it were only pulling water i think (i have not tested this theory). But on top of that, its pulling half the wattage. So its working less to do its job. These combined tell me that this should increase the life of my pump.

 

But if it does create more friction in the volute, then that would increase heat. Then again, we are pulling half the wattage. Round and round we go!! (laugh)

 

Plus we haven't even touched the pinwheels.

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We're gonna have to agree to disagree then. I encourage Jay to research this more deeply himself' date=' there's a lot of information on this available out there.[/quote']

 

Not trying to be combative Andy. Do you anything that backs up what you are saying? I am interested. It just goes against my thinking on this.

 

I've googled it and cannot find any data to back up the idea that the life of the pump is shortened, only hearsay.

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There are some good posts at RC, written by people with chops. I don't have anything bookmarked, but IIRC one of the better threads started off with a discussion of the effects of calcium build up blocking the special cooling channels inside Red Dragon skimmer pumps. I may try to Google it later, I'm at work right now.

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Unless the mesh significantly increased the weight of the impeller i don't see how it would reduce the life of the pump. In contrast, the mesh should be helping pull more air in, which in turn would make the impeller easier for the pump to spin, which would INCREASE the life of the pump IMO.

 

Jay just to clarify. With the airline plugged it runs full bore no problems. Then when you open the airline it cavitates?

 

Sometimes its not what is said its how its said.

 

The gentleman who told me this information had no stake in doing so. He has modded many skimmers and told me that the pumps wont last as long, he did side by sides with mesh vs pinwheel. The only reason I spoke up was to let the original poster know about this. I didn't think it would get side tracked into what you believe or don't.

 

If you go to RC you will find that the some of the biggest supporters of mesh modding have since gone back to pinwheels after using them for 6-12 months.

 

I have to rely on what others tell me. If they are not trying to sell me something or don't stand to gain anything it holds more weight with me over someone who has an agenda.

 

But you all need to read my tag line again, because its true.

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You could be over drawing air with the mod, creating an inefficient mix. Try putting a valve on the air intake and dial it back just a tad, see if that makes a difference. Pumps are engineered to work with specific ratios, just like car engines. If you get outside those tolerances, you may find a drop back in efficiency.

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Sometimes its not what is said its how its said.

 

The gentleman who told me this information had no stake in doing so. He has modded many skimmers and told me that the pumps wont last as long, he did side by sides with mesh vs pinwheel. The only reason I spoke up was to let the original poster know about this. I didn't think it would get side tracked into what you believe or don't.

 

If you go to RC you will find that the some of the biggest supporters of mesh modding have since gone back to pinwheels after using them for 6-12 months.

 

I have to rely on what others tell me. If they are not trying to sell me something or don't stand to gain anything it holds more weight with me over someone who has an agenda.

 

But you all need to read my tag line again, because its true.

 

Well i'm someone who uses my brain to understand why things work instead of just taking in what i'm told as fact. This does not make complete sense to me. I never said i was 100% sure i am right. I was even explaining my train of thought that brought me to a conclusion. This is how you create discussion. In turn, you may learn something from a discussion.

 

You just went with the quick personal jab and no explanation. Touché.

 

So are you just broadcasting you are not a nice person? Is that the point?

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Well i'm someone who uses my brain to understand why things work instead of just taking in what i'm told as fact. This does not make complete sense to me. I never said i was 100% sure i am right. I was even explaining my train of thought that brought me to a conclusion. This is how you create discussion. In turn, you may learn something from a discussion.

 

You just went with the quick personal jab and no explanation. Touché.

 

So are you just broadcasting you are not a nice person? Is that the point?

 

Did OIAB post in here?(naughty)

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Well i'm someone who uses my brain to understand why things work instead of just taking in what i'm told as fact. This does not make complete sense to me. I never said i was 100% sure i am right. I was even explaining my train of thought that brought me to a conclusion. This is how you create discussion. In turn, you may learn something from a discussion.

 

You just went with the quick personal jab and no explanation. Touché.

 

So are you just broadcasting you are not a nice person? Is that the point?

 

 

Your right. I am sorry.

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Well i'm someone who uses my brain to understand why things work instead of just taking in what i'm told as fact. This does not make complete sense to me. I never said i was 100% sure i am right. I was even explaining my train of thought that brought me to a conclusion. This is how you create discussion. In turn, you may learn something from a discussion.

 

You just went with the quick personal jab and no explanation. Touché.

 

So are you just broadcasting you are not a nice person? Is that the point?

 

Dude, not a very political post or stance to take from a board member, maybe things have changed since this group was formed, but I would think you as a board member would tread with a little more caution as a public representative of the non-profit. I am disappointed to see remarks like this, and I think he deserves an apology, and move on by you in this thread.

 

Take the high road here.

 

Reporting this for a lock before it gets ugly.

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Mesh mod now for a few years, output was visually the same after mod and have had no issues with pump over the years other than much better performance. Your theory may be true but after a few years with mods and pump still running like new I would mod every skimmer with needle wheel I come across if it has the capability to pull the mod mesh. Lets move on with more facts.

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Unless the mesh significantly increased the weight of the impeller i don't see how it would reduce the life of the pump. In contrast, the mesh should be helping pull more air in, which in turn would make the impeller easier for the pump to spin, which would INCREASE the life of the pump IMO.

 

Jay just to clarify. With the airline plugged it runs full bore no problems. Then when you open the airline it cavitates?

 

Exactly. I removed the mesh and it does the same thing. Runs full bore then when I put the hose on it cavitates and rattles. I even tried to limit the air and find a happy medium but as soon as it gets bubbles it quits almost completly. I can even see water almost to the top of the skimmer neck where it should have lots of foam.

 

Jay

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