Sump Flow Rate Debate.

[wrightme43]

Ok here is the question.
How does flow rate thru the sump effect SKIMMER efficency and Heater effecency?
Here is my opinion
I believe all of the water in the system can be looked at as one piece of water. It is a closed system. Bear with me. If I set a skimmer in my tank (not the sump) and I have a flow rate of 5000 gph in a 100 gallon tank or I have a flow rate of 500 gph in a 100 gallon tank. I believe the skimmer will opererate the same. I may remove more stuff in the 5000 gph tank because of particle supension but that would be the only change, as I see it.
If I have a flow rate of 5000 gph thru my sump or 500 gph thru my sump I cant wrap my brain around the concept that it would change the effency of my skimmer all of the water in my mind is the same water. I can not see how it would effect it.
The same goes with a heater. It is a closed system. Any heat I put in will be spread thru the system in a equal manner. If I slowed the sump flow down enough to get a actuall temp. differential between the tank and the sump, that is the only way I can see it to cause a problem.
I want to see peoples opinion and ideas on this concept. Some of us have been discussing it on another thread but that is not the topic, and it is my fault it got off topic.
So here it is. What do you think?
Steve

 

[moonpod]

I personally advocate 5 turnovers or so through the sump. That gives the skimmers and heaters/chillers, whatever plenty of "face time" with the tank water. Minimizes pump size. Makes overflow noise and flow easier to manage. Get the rest of your flow in other ways.

 

[mojoreef]

It really has alot to do with what you have in the sump. Most of the sump restrictions are related to removing bubbles from the skimmer or from the drain out puts, if you run the water to quickly through it you wont be able to get rid of them. If your run calurpa or a refugium in the sump its all about contact time so the slower the better their to. As per you skimmer analogy the more particulate you can have in suspension the better chance you have at removal (depending on how you skim) .
Personally I like to run the sump slow and worry about flow from CL's in the tank.


Mike

 

[les]

I flow 4000GPH throughout my sump for my 175 tank.
The skimmer seems to do a good job, the heaters rarely come on, (due to two 400 watt MH) and cooling isn't much of a concern.

I have a few points to make here, DonW stated that flow rate through or around a heater has a greater heating capacity of slowed down. The analogy used was hold your hand over a candle, the faster you move your hand the lower the burn rate. While thats true, a better analogy would be to put that lit candle in a closet. If you wave it around real fast is there less heat going into the closet? I think not.
On the sump/skimmer flow rate question, the link provided was less then clear on what is the best flow rate through a sump. I felt that the only thing they found was the DOC levels were reduced when flow rate was matched to the skimmer. To me this seems to be more a question of skimmer efficiencies rather than flow rates. To follow the advice/conclusions of that study a person should purchase a skimmer that is big and then match the sump flow rate with the skimmer flow. If I were going to do this then I think I would go one step further and cut the sump flow to about half of the skimmer flow. That would ensure that your are getting the lowest concentrations of DOC returned to the tank.
The one person I asked that had tested their water for DOC and noticed changes in DOC concentrations based on sump flow also stated that they could see to effect of the tank critters. This seemed to be true of both levels of DOC, high or low. There may or may not be any long term harm to corals and fish living in elevated DOC environment, that will have to be tested by experts.

 

[fishermann]

The water is not a closet that is not moving with a heat source being moved around fast. The water is the thing flowing or moving fast with the heat source stationary as with the hand analogy and the water is loosing heat to the air also and the faster it moves the more heat transfer you well lose to the atmosphere. As for the DOC's being harmful to the corals and fish, they can within reason take the little spike that was noticed in the different flow rates, but the algae is going to love getting a second chance at getting to eat that detritus.

 

[forsaken541]

Its funny that this came up because I recently without knowing it put this to a test. My sump has about a 5 gal rubbermaid on top of it that I plumbed with a 1 inch inlet twords the bottom and a 1 inch gravity outlet to the sump below. My skimmer and return pump are in the sump. Now the fuge on top has more flow through it being a smaller volume (about 1/4) than the sump below. I took my 300W heater and moved it from the sump where I had it between the baffles and moved it to the fuge. The tank temp when the heater was in the sump stayed at 80 almost all the time but when I moved it to the fuge the tank temp dropped to between 76 and 78. So I think that having your heater in a lower flow environment makes it more efficient. I attached a crude drwing of my sump setup to help with the visualization.
Erik

 

[DonW]

While thats true, a better analogy would be to put that lit candle in a closet. If you wave it around real fast is there less heat going into the closet? I think not.
On the sump/skimmer flow rate question, the link provided was less then clear on what is the best flow rate through a sump. I felt that the only thing they found was the DOC levels were reduced when flow rate was matched to the skimmer. To me this seems to be more a question of skimmer efficiencies rather than flow rates. To follow the advice/conclusions of that study a person should purchase a skimmer that is big and then match the sump flow rate with the skimmer flow. If I were going to do this then I think I would go one step further and cut the sump flow to about half of the skimmer flow. That would ensure that your are getting the lowest concentrations of DOC returned to the tank.
The one person I asked that had tested their water for DOC and noticed changes in DOC concentrations based on sump flow also stated that they could see to effect of the tank critters. This seemed to be true of both levels of DOC, high or low. There may or may not be any long term harm to corals and fish living in elevated DOC environment, that will have to be tested by experts.

I think John put it better than I, your tank is not a sealed closed. After ruducing my flow my second heater never comes on. This saves me the electricity of a second 250w heater (more efficient).

As for matching the skimmer to the flow. Most skimmers are rated in tank capacity. I dont really believe that most people take flow into considerartion. By not doing so you are lowering the efficency of the skimmer. I for one do not have a rated skimmer so I adjust my flow to match the skimmer, in turn lowering organics (more efficient).

Do elevated levels of DOC's effect tank critters? I thought this was the whole idea behind the skimmer, reducing DOC's. I dont think we need a so called expert to tell us the long term effect of elevated DOC's. The goal is a nutrient poor enviroment attempting to match that of the ocean. Making the skimmer more efficient helps to accomplish this.

Your tank for example. If you decided that you must have all 4000gph through the sump, then went out to buy a skimmer to match this flow rate. You would have to buy some real monster skimmer that probably doesnt fit in the living room.

The idea behind the conversation is increasing the efficiency of the system. Keeping in mind that the pennies add up to dollars. The dollars equate to more coals I can buy.

 

[les]

So Don,
In my new 400 gallon setup, with a skimmer rated at 800 GPH, would it be advisable to reduce the sump flow to 400 GPH?
If I were to do this then what about the refugium? would that flow be "tee'd" off of the 400 GPH line or should it be a separate feed?
The more I think about this the more inclined I am to try it. I already have the 4000 GPH pump and the skimmer, (ETSS Gemini 800) but would need to purchase a lower flow rate pump.

On second thought, I have in the shop a Dolphin DP900, this won't give me "half" the flow of the skimmer but will be alot slower than the 4000. With head loss of the DP900 I should be around 650-700GPH.

 

[les]

And then what about the refugium? Should I skim the water to it or from it or just pump back to the tank?

 

[DonW]

And then what about the refugium? Should I skim the water to it or from it or just pump back to the tank?

Les,
I really know nothing about refugiums, never had one. I think a 1k gph would be a good return pump. This way you can turn it down a little at a time to see what works best. I assume you have a closed loop planned. I'm with mojo in the sump is just for water processing and closed loops are for in tank circulation.

Don

 

[mojoreef]

Ok I am kinda lost in this. What would the sump gph have anything to do with the skimmer??? The skimmer is going to skim based on the pump that feeds it and the efficiency of the skimmer itself. It doesnt matter. You have to take the total water for the system. If its a 1000 gallon tank and the skimmer does 1000gph then its going to take an hour to run the tank through the skimmer. If you sump is only pushing 500 gph it also wouldnt matter as no skimmer can completely skimmer the water on one pass. Or am I missing something here?? lol

On the Refugium Les its a completly different animal, this also applies for remote dsb's and Mud systems. In this case its all about contact time, biological process happen alot slower, so the slower the water flow through it the better.


Mike

 

[Scooterman]

I was just itchin to jump in here but I don't see the argument, The only reason I use a sump is to locate equipment, I think Mike took care of the rest about the skimmer. So with that said, why would a higher flow rate through the sump be necessary?

 

[wrightme43]

The reason I brought it up, is some people think that high flow rates thru a sump hurts the performance of the skimmer and the heater. I do not think it can. The discussion was started on a different thread that was unrelated. So, I started one here. My point is flow rate thru a sump has no bearing on tempreture transfer from a heater or skimmer performance. In a refugium it makes perfect sense to slow it down, In a sump which could be located along side, below, in the basement, out in the garage, in your neighbors house, wherever, the skimmer is still going to do the same thing, the heater is still going to put the exact same amount of heat into the water. I brought it up because some people can not afford to, or have a set up glass tank, or for any other number of reasons, can not put in a closed loop and use thier return pump to power sea swirls, spray bars, and any other number of flow devices. I have seen people be told that they cant do that because thier heater wont work, or thier skimmer wont work right. I do not believe that. So I want to know what you all think. Steve

 

[DonW]

Steve,

I put your theory to the test. Yesterday I increased my sump by about 400gph.
At 10 last night heater 1 one was on when I went to bed. This morning heater 1 and 2 were on. Usually only heater 1 comes on sometime during the night and is off soon after the halides come on.
My skimmer produces about 12 fl oz. per day has done this for months. Yesterday at 6am the cup had 12oz and was emptied. Today the cup had less than 6oz. I'm gussing at this rate the ozone should fire up in the few days since orp is also falling for the first time in weeks.

Could you explain why this would happen?

Don

 

[les]

Ok All,
Here is what I decided to go with. After testing the closed loops systems on my new tank last evening (I shot waves over the opposite wall).
I will rely on 3 closed loops pumps for tank flow/current. I will use a Dolphin DP 900 for the sump return pump that I can close down to app. 1/2 to 3/4 the through put of the skimmer. At 800 GPH skimmer rating, that in theory will see the tank water through it 1.5-2 times an hour.

By the way, the two closed loop systems tested last evening are only plumbed with two tank jets each from the end my 8 foot long tank. It not only shot waves over the opposite end, the tank looked like a jacuzzi on steroids. I can't wait to see it with the third pump in place.
If anybody wants to see pics of that, then contact Ed Hahn.

 

[Scooterman]

DonW do you feed your skimmer from the same return pump?

 

[wrightme43]

No, Don. I dont understand it. My brain just can not see how that would cause that. I am not saying in way that is not the case. I just cant understand it. That is why I brought it up. For me I have 75 gallon tank and flow 1000 gallon a hour thru a 20 long sump. I have no problem with heat, or my skimmer. I know every tank is different. Please dont think I am attacking you. I like you alot Don. I think you are a great guy. I just dont understand and want to, get this hashed it. If it effected my tank the way you tank is being effected. I would have problems with mine too. I think anyway. That is what my brain is telling me. Maybe it has something to do with another componet that one of us is using and the other isnt. I just dont know. Steve

 

[DonW]

Steve,
Really my tank has no problems. I am simply pointing out that sump flow will cause changes in the system. For me decreasing flow improves performance of both the heater and skimmer. Big difference between a problem and efficiency. Works fine, temp stays stable. Just cost more electricity to do it. Could get more skimmate by raising the water level in the skimmer. This would just be a patch for the lower efficiency.

Scooter,
My skimmer is just a needle wheel diy knock off. Its fed by its own pump.

Don

 

[wrightme43]

Sorry That is not what I was meaning to say. I dont communicate well sometimes. My apoligies. I was not meaning that you have any problem with your tank at all. I was trying to say that I would probley slow down the flow rate or change something too.

 

[Scooterman]

At a slower flow rate my tank actually runs cooler, either longer water surface to air or maybe the pump has less strain. Skimmer produces the same regardless. Heaters coming on or off may mean that the water flowing faster requires them to work together but doesn't mean that your actually requiring more heater times. So, what does this mean, It means if we want more information, we will need to test under stricter conditions & see the results.