Who rates skimmers

[mr.wilson]

Originally Posted by sphelps

Comments like this make me question your design experience, while I wouldn't expect most hobbyists to understand pipe dynamics I would expect an experienced designer to understand some basics regarding flow mechanics in piping systems. Static head is only one part of head loss and even with correct pipe sizes and flexible pipe friction losses are large and plumbing the pump into the basement would add huge losses from friction. You can never completely avoid elbows, tees, unions, and ball valves. These all add significant losses. In addition adding systems to rotate flow will also add significant losses. But your major losses will always come from pipe length and over time your roughness factor increases adding more friction to the system.

I stated there was no head loss, not that there was no friction loss. I was responding to your comment about head loss with closed loop pumps being significant. If you use the RC flow calculator you will see that an elbow, two ball valves and 15' of pipe will drop a Blueline 70 from 1710 GPH to 1620 GPH. This is an example of a closed loop pump located in a basement below the tank, you would have less friction if it were located directly below the tank and of course you could add friction with other plumbing. I simply don't see this as a significant issue, and you never mentioned it in your comparison for likely the same reason.

A good power head like a controllable tunze or vortec is a far superior option. They can be controlled by microprocessors and tuned to a frequency that matches your tank dimensions resulting in maximum water movement with minimal power consumption. The flow control is electronic which allows for unlimited possibilities for both flow control and dynamics. To say a closed loop can do this better is just being closed minded. You're comparing a $1000 elaborate closed loop system to a $50 maxijet, try comparing apples to apples. They also produce much less vibration than most external pumps and will always come out on top in efficiency. Heat transfer through a Tunze is minimal wouldn't add sufficient heat to a system to require cooling. Vortecs have there motors external so they would add even less heat to the system.

What are you trying to accomplish with variable speed on the Vortechs or Streams? An intermittent reduction in output only reduces the volume of water you are moving (and electrical consumption). An Oceansmotions 4 Way maintains the same flow rate within the tank while offering a passive surge and allows detritus to momentarily settle for coral feeding, then pick up again before it reaches the substrate. If you time the ports properly, detritus can be passed from one end of the tank to the other using 50% less flow than four static effluents. A powerhead system is limited to side to side flow, and while one side is off, your flow is now at 50% capacity. A closed loop pump with a 4 way is always delivering the right amount of water to right location at all times. You would need twice as many powerheads to make up for the time they are not running for side to side motion.

The only real advantage to a closed loop is that intakes and outputs can sometimes be hidden better, however both Tunze and Vortec offer solutions for this as well. Closed loops can also be a better alternative for extremely large aquariums where you simply can't get power heads large enough but most hobbyists don't have tanks that large.

What are the solutions that they offer. The Dana Riddle article confirmed some of the flow claims so they got some points with me for that, and I would be happy to hear about more hidden benefits.

I've used Tunze power heads in my tanks and others I maintain for well over 5 years and the very few problems I have had where quickly fixed free of charge by the manufacturer despite the fact that the warranty was expired and I had no proof of purchase. I can't say the same for many external pumps I have used which have certainly proved to be less reliable than the power heads I've used. External pumps that use external motors are far from reliable, seals often fail which quickly leads to bearing failure.

Shaft driven pumps like Sequence are not suitable for marine aquariums so I'm not surprised you had problems, but that is like me directly comparing a maxijet to a Vortech, which I have not. The main problem hobbyists experience with external pumps is sumps running dry (which would also happen with a submersible pump), and saltwater dripping on the motor (which is negligence). To a lesser extent sand in the impeller or dust in the fan also occur, but once again these same people would be negligent with powerheads. I have experienced a 1% return or repair issue with external pumps, and although I don't use powerheads, I always see a mountain of them at local aquarium stores return bins and replacement parts are well stocked, while replacement parts for external pumps is a non-issue.

Closed loops are usually done as a cheaper alternative to expensive power heads, not the opposite. And the they slowly being phased out as more and more advancements are being made with DC power heads. An external DC pump could make a come back for CLs but so far something reliable and cost effective hasn't been made available to us.

Sequence makes a DC Dart. The only application I could see is a series of deep charge marine batteries for a backup system but personally I prefer air lifts.

Head Loss Info, FYI

Excel Sheet

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