100% drain into skimmer

[fritz]

100% drain into skimmer / LOW Gph return

Ok so I just can't leave my sump/skimmer alone. I decided last night to cut my return pump back to about 10% and plumb 100% of my drain directly into the skimmer. Every drop of my drain water now passes gravity fed into my skimmer.

I thought of this because I was looking at my return pump. 65 Watts for about 900 Gph. My circulation pump pushes 3,000 GPH at 14 watts. I don't need to use my return pump for circulation and most of my drain water passes by my skimmer in the sump and goes back into the tank. My skimmer should only get about 125 GPH fed into it which conventional wisdom would say is crazy to have on a return pump. Really who uses a 125 GPH return pump! Well I decided to try it.

Upon first turning everything back on I instantly got some grey bubbles at the top of my bubble column. I'll report back tonight with how it is after 24 hours of running like this.

 

[pecan2phat]

Welcome to the "Gravity drain fed Skimmer" club

 

[fritz]

haha
So I guess the really low GPH return is more common than I thought. I always see people using these massive return pumps and "T"ing off a small piece of the drain to their skimmer.

 

[herman]

:beer:

 

[cali_reef]

Fred, I think you are the only one cutting back your return pump and draining 100% into the skimmer. Why don't you just put on a diverter valve and turn your pump back to full speed??

 

[fritz]

Because that would defeat the point!? Pshht.

I was thinking about how my circulation pumps move a LOT of water at low wattage but my return pump moves very little water at a much higher wattage. With my return at 100% most of the water coming down my drain rushes past my skimmer and goes back up into the tank (wasted energy IMO, plus it missed the skimmer, also a waste.) At this point my return pump is 80% circulatory and 20% return. On top of this the top layer of water being skimmed into my drain is being mixed with lots of extra water since I'm running 800 GPH through the drain. Since my skimmer only needs about 130 GPH only 1/7 of the drain water hits the skimmer.

Now if I run my return at 150 GPH I can send every last drop through the skimmer, have the outlet push water over some LR in the sump and then go to the return pump. In this scenario I'm taking a much finer slice off the top of my tank, hopefully getting more film and putting it right into the skimmer rather than only 1/7 of that film going into the skimmer.

In theory I think it makes much more sense to use a low GPH return and put 100% of the drain into a skimmer. (Only applies to the non beckett obviously ) So far so good, I had a problem dialing the skimmer in right the first day and flooded the collection cup but I got it right now. I haven't had it setup long enough to get good data but it appears to be running much more efficiently. I should be able to get a good guage in the next few days.

 

[ming]

Throttling the return pump doesn't save on electricity. You would have to change out the pump for a lower wattage return pump. If you're going to use the same pump, I would just let it go full on so at least the corals have more flow

 

[cali_reef]

In addition to having the water skimmed, you also have to make sure the flow rate thru the sump will be enough to "carry" heat back from the heater in the sump, the slower rate will cause your temp controller to cycle a lot more than a faster flow thru the sump. Summer evaporation cooling in the sump will not work as well with the slower flow. Dosing two part in there will also have to be spaced apart longer with the slower return.

I think 5-10x return rate are more optimum for typical tanks.

 

[PalmTree]

I'm having a real tough time visualizing this set up. Do you have a pic?

 

[herman]

I'm having a real tough time visualizing this set up. Do you have a pic?

Visualizing this particular setup? Or gravity fed skimers in general?

 

[Deanos]

I'm having a real tough time visualizing this set up. Do you have a pic?

Something like this:

 

[MO~IDOL]

some good info for gravity feed set ups

http://reefcentral.com/forums/showthread.php?s=&threadid=848756&highlight=gravity

 

[meschaefer]

In addition to having the water skimmed, you also have to make sure the flow rate thru the sump will be enough to "carry" heat back from the heater in the sump, the slower rate will cause your temp controller to cycle a lot more than a faster flow thru the sump. Summer evaporation cooling in the sump will not work as well with the slower flow. Dosing two part in there will also have to be spaced apart longer with the slower return.

I think 5-10x return rate are more optimum for typical tanks.

You often see return return pumps discussed in terms of total tank turn over, but if your concerned about the carrying of heat from the sump to the display and the dosing of 2-part wouldn't it make more sense to discuss the turn over in terms of # of times that the sump turns over as opposed to the main display tank?

I think to a certain extent that this is "old" thinking, not necessarly correct or incorrect, but almost dogmatic in that it hasn't been rethought through in terms of the newer technology that is available. It used to be that most of your tank circulation came from your return pump. But now that there are a number of low wattage "power heads" available that move alot of water, for a lot of people circulation is not dependent on tank turn over.

 

[cali_reef]

The 5-10X I am thinking of is to make sure enough water is circulated through the heat(or cool) source in order to have a stable temperature, the slower flow passing the heat source can cause the main tank's temperature to drop while the heater's sensor and heating element in the slower moving sump takes effect. I am not thinking this in terms as total waterflow\movement in the tank..

 

[meschaefer]

The 5-10X I am thinking of is to make sure enough water is circulated through the heat(or cool) source in order to have a stable temperature, the slower flow passing the heat source can cause the main tank's temperature to drop while the heater's sensor and heating element in the slower moving sump takes effect. I am not thinking this in terms as total waterflow\movement in the tank..

Absolutely, all I am saying is that there is a minimum flow rate that will allow the heating/cooling element to keep the tank temp stable. And while the math of fluid dynamics is beyond me, I think :scratchch that it might be alot less than 5-10 times turnover.

The problem of the sensor described above could be overcome by placing the sensor/heater directly in the path of the water coming from the display tank. Even better, for those of us that are using a seperate controler place the sensor in the display tank.

Perhaps it is better to think of this in terms of total tank turn over, rather than sump turn over (never said it wasn't just wanted to re think the idea).

 

[Deanos]

Since my skimmer only needs about 130 GPH only 1/7 of the drain water hits the skimmer.

If you remember yesterday, I mentioned we need to determine what skimmate is made of. If it's predominantly particulate matter, your method will give your skimmer the best chance of removing these items. However, if skimmate is mostly dissolved organics/saltwater, you may not need to skim 100% of your drain water to efficiently remove these organics. :scratch: I'm hoping someone better versed in chemistry can shed some light, but I imagine dissolved organics diffusing equally throughout the tank's water volume, like the calcium/magnesium additives some of us use. When measuring calcium levels, a few ccs of tank water tells you the state of the entire tank.

 

[herman]

Well this is of course another case of many ways to skin a cat. 100% into the skimmer is a good thing and in this case the skimmer requires less then 200gph. I think its been at least 10+ years since Cali has used a skimmer that requires less than 600gph. The setups will differ depending on the plumbing. Fred relies on streams for flow within the tank but Calis setup is a bit more complicated. Its a case of scooter vs jetbike. They both get the job done.

The problem with 100% water into the skimmr is controlling the surge and turbulence in the pipe which is an absolute no go in the world of gravity feed.

Im more in the middle. My skimmer requires 610gph and no surge. I rely on my return pointing to the back of my tank for flow in that area while the streams take care of the rest. I have 2 1.5" drains. One drain goes straight into the sump and controlled by a ball valve to regulate flow to the other drain. The other has a T fitting followed by a ballvalve. Any surging and gurgling gets taken care of and excess water goes into the sump via the T. At least that ensures constant flow.

 

[meschaefer]

If you remember yesterday, I mentioned we need to determine what skimmate is made of. If it's predominantly particulate matter, your method will give your skimmer the best chance of removing these items. However, if skimmate is mostly dissolved organics/saltwater, you may not need to skim 100% of your drain water to efficiently remove these organics.

If it is made up of both, then skimming 100% of your drain water would be reccomended...no? If it is T'd off, a percentage of particulates is diverted away from the skimmer. If all the water sent to the sump passess through the skimmer, then you get all the particulates entering the sump (assuming 100% efficency by the skimmer-I know don't assume, something about being an ass). The lower flow has no effect on removal of dissolved organics, as the same amount of water is being skimmed.

 

[fritz]

So far I'm not seeing any issues with temperature or temperature readings. I think this is due to my temp probe being (as meschaefer stated) directly in the line of flow. I keep my temp probe and ph probe inbetween my baffles so that I can visually guage how much water is rushing past them. Even though 200 GPH of return flow seems small for a 58 gallon tank it is a lot of flow for a 20 high sump with a 10" water level. Looking at my baffles there's a good 1/4" of water flowing through them which I think is plenty for my temp and PH probe to get a good reading. I dose 2 part into the display and it does of course take longer to register in the sump then with a higher return rate but it gets there.

As to Dean's points, well I have no idea. I expect that if we were able to test drops of water from different layers of the tank (left stagnent) the surface (near the film) would be the worst. My thinking was that less return would also equal more concentrated, or at least more effecient, skimming of the surface slime. As meschaefer stated above I'm still skimming the same amount of water as when I had a 900 GPH return I'm just not letting any of the water rush past the skimmer and go back into the tank anymore.

 

[meschaefer]

I have taken a particular interest in this thread beacause I need to redo the plumbing, since I got my recrirc skimmer (DAS-EX2), and a new sump in the last month. I want to plumb the skimmer off the drain and I also wanted to slow down the flow through the sump as I am having micro bubble issues. I always had them, but thought it was due to the jury rigged sump. It has been suggested to me that I may have to much flow through the sump, and the bubbles are carried along with the water over the baffles.

That being said, I am planning on about 5x total tank turnover compared with teh 10x turnover that I currently have. I am picking up my nano streams this weekend to pick up the slack. I will not be running all of my tank water through the skimmer, but will have the more traditional 'T'.