External v.s. In-sump skimmers

[5pacey]

I am building a 90 DT w/a basement sump setup and originally was planning on using just a in-sump skimmer (SWC 160). But... since I can do whatever I want in the basement I started thinking that maybe doing an external skimmer would have some benefits. For one I don't have to deal w/water levels and the sump can be smaller. etc... that said, I've been looking at PM's and AquaC's ... but I am confused by one thing. Say Bullet 1 or 2 or AquaC 180, they seem to require monster pumps to run! A Mag 18 for example is rated at 1800 GPH! That's monster flow, and it's all going into the skimmer! So going by the flow it sounds like that skimmer is calculated at a 360 G system assuming the standard 5x sump water throughput! But it's a small skimmer relatively speaking... so what's the deal? Not to mention that those pumps require small electric plants to run.

To contrast this w/in-sump ... for example a SWC 160 has a 20W pump whereas Mag 18 is a 140W pump!

Incidentally, I plan to use Mag 18 for my return pump from the basement (rougly 12' head and 25' horizontal run). So I am having an issue w/the concept of running the same pump w/no vertical head pressure just to power the skimmer.

Where am I getting lost here... ? Are EV180 or Bullet 2 for example really aimed at >300 G systems or they are just dinosaur skimmers (or perhaps all external skimmers are like that) that require little nuclear power plants to run?

Spacey :eek1:

 

[sirreal63]

Instead of looking at skimmers that use downdraft or injection that require large pumps, you should be looking at recirculating skimmers. Recirculating skimmers are the same as regular skimmers except the recirculate the water in the skimmer, can be internal or external. No need for large pumps to run them and they work. Here is a link to get you started, there are many brands out there, this is just a quick look.

http://coralvue.com/category/products/protein-skimmers/skimmer-types/external-skimmers/

 

[5pacey]

Instead of looking at skimmers that use downdraft or injection that require large pumps, you should be looking at recirculating skimmers. Recirculating skimmers are the same as regular skimmers except the recirculate the water in the skimmer, can be internal or external. No need for large pumps to run them and they work. Here is a link to get you started, there are many brands out there, this is just a quick look.

http://coralvue.com/category/products/protein-skimmers/skimmer-types/external-skimmers/

Jack,

Thx, the re-circulating skimmers did not escape my attention. I guess I started looking from the "roots" so to speak since Precision Marine and AquaC have been around forever and the skimmers in question seem to have really good ratings. Other than AquaC's "injection" system and the main stream venturi I am not all that familiar w/all skimmer designs. Recirculation skimmers, at least to me, appear to be relatively new. Idea sounds good. Also, speaking of wattage consumed, they too have at least 2 pumps (in case of the simple ones) - 1st feeder pump, 2nd recirculation pump. The larger ones, have two or more recirculating pumps so that's even more wattage.

But lets say in my case I could get away w/a relatively small model. So I am going to need looks like a 20-30w feed pump and then the recirculating pump is probably about twice that size. so total of 90w or so to run the skimmer. I guess that's better than 140w (mag 18) to run Bullet 2 or ev-180, but still way more than 20+ watt to run my SWC 160...

Again... why is this? Is it because those are just more powerful/better performing designs (at the cost of more wattage)? Are there no external skimmers w/the traditional feeder pump + venturi design that work well?

Spacey :hmm5:

 

[sirreal63]

Recircs have been around at least 10 years, maybe more. It is what Deltec, H&S and other top performers have been for a long time. I use a small feed pump, a MJ works great or you can feed from overflow. Downdrafts process a lot of water and fast and make sense for large systems, for a 90 I would use a recirc rated for 180 gallons and it will do the job, though you could use a smaller skimmer as well. I have used an ASM G3 since 2004 or 2005 and have zero complaints.

You can also convert your SWC to a recirc, it isn't hard, just a plumbing thing.

 

[chuckreef]

Again... why is this? Is it because those are just more powerful/better performing designs (at the cost of more wattage)? Are there no external skimmers w/the traditional feeder pump + venturi design that work well?
Spacey :hmm5:

These types of skimmers use the pressure head of the water (produced by the pump) to produce the air bubbles for the skimmer. Although they have high flow ratings at lower head values, when plumbed to an injector or other device that applies a significant backpressure (i.e., headpressure) on the pump, the flow drops significantly. Look at any pump curve for a centrifugal pump and compare the flow at high and low head pressure values. The smaller pumps on modern skimmers do not rely on head pressure to create air bubbles; they (very efficiently) create a lot of air bubbles using a venturi/ pin wheel (or mesh or needle, etc).

The older designs are not necessarily better becuase they use more power, they are just less efficient.

My suggestion would be to use your modern cone skimmer, located in a separate shallow pre-sump elevated above the main sump. This pre-sump would be only ten to twelve inches deep and would provide easy acesss to the skimmer, and could be easily bypassed.

 

[viggen]

yea... RC'd skimmers have been around for a while I think most just do not want to spend the extra money on them.

Like mentioned the Bullet, AquaC, ETTS are all excellent skimmers however like stated they usually pay off more when they are put on very large setups. The reef devil from etts (or is it eets... I dunno) I used years ago on my old 90g reef. It worked but like mentioned needs a pretty strong pump to get it to do anything... just the nature of the beast.

On my larger ER I do not have a feed pump but I ran the dirty water line directly from the overflow box. If you go the RC route you only need 1-1.5x's a hour turnover through the skimmer so on your 90g you would only want 90-150 ish gph of actual flow... thus a pretty small pump.

Like mentioned you can easily modify a existing skimmer to be a RC skimmer. Just drill a extra hole or two in the body... a little plumbing & your good to go. I did this on my ASM G3 (which replaced a reef devil) & my ER 12-2 which I converted to a RC500. I sold my G3 a while ago & purchased a used ER rs250... going to convert it to RC as well since I do not have a proper sump on either tank to maintain 8or so inches of water depth.

 

[viggen]

sorry about that.... double post