Flow Rate Through My Sump
 

So I switched out my return pump yesterday on my 70 Gallon FOWLR tank. Here’s my setup and questions. Maybe someone can help

70 Gallon Tank w/ 20 Gallon Sump
Pump: Simplicity DC 1000
Skimmer: Reef Octopus 150

I tried to use a head loss calculator for head loss. I’m getting conflicting information from the one on Reef Cerntal (the pump isn’t listed there). I’ve got 5 feet of 1” tubing going back into the tank with two 90 degree elbows. My calculations tell me I should be somewhere in between 500 and 700 GPH after head loss. Can anyone pin down a more accurate number for me?

Once we get that number nailed down what kind of flow rate should I run through the tank with the skimmer I have? I’m thinking around 350 GPH possibly? The DC 1000 is adjustable so I need to know an accurate flow rate so I can adjust it down so the skimmer works the best it can

Thanks!

The skimmer performance should not be affected by the turnover rate as long as it is reasonably high. There is no advantage to turning it down for skimmer performance. The. DC1000 will only deliver about 500 gph at 4 ft so I would think something like 400-500 gph is what you could expect at full speed which should be good for That size tank.[

I think there is no correlation between skimmer and sump flow. Worrying about matchin sump turnover to skimmer processing is, I think, to fundamentally misunderstand how a skimmer works ..... or doesn't work.

The whole point of the recommended flow rate though a sump is so that the water is processed by whatever equipment in the sump at close to that same rate..

Flowing water through the sump faster than it can be processed is just a waste of energy IMO..
In the perfect world a skimmer would state "250GPH" or whatever is capable of processing and you simply match your sump flow rate to that..

Unless someone can tell me what other reason one would have for the flow rate through a sump..

You’re overthinking this. Buy the biggest pump you can afford and fit, use the biggest plumbing possible, install the plumbing with the least number of angles, then set your skimmer to max. That’s it. You don’t need to optimize, you won’t be correct and you’ll drive yourself crazy. The only way to be right is to measure with an FMM or other flow meter.

The tank has been set up for about 10 years now. The only thing that was swapped out was the return pump

I did some calculations. It looks like my skimmer runs about 200 GPH and I’ve got the return pump running at about 270 GPH. I’m going to wait a few weeks to see how my skimmate looks

So many conflicting opinions in regards to high flow vs. low flow out there. lol

Believe it or not I used to have a handle here under Killagoby but it’s been so many years away from the forum that I couldn’t retrieve that account. Hence the 2 posts instead of the few thousand I used to have

Few think about exactly why they are draining water down and pumping it back up.. Just pumping it is useless/inefficient if its not being treated in some manner or another..

I asked Randy Farley Holmes this same question in a diff forum, as I am tinkering around the idea of Triton or ATI Essentials and can't wrap my head around why 10x flow through the sump. He stated (much more eloquently than I will be able to regurgitate) that from a chemistry perspective nothing will happen in 10x turnover that wouldn't happen in 5x. Stated differently what would happen in your sump every 6 minutes versus 12 minutes?

exactly..
I can't see how any more than a 1 time an hour turnover is needed as far as water chemistry is concerned.. and 1 time and hour is probably more than needed to keep parameters stable enough between display and sump volume.. I just picked 1 hour for discussion sake really as its typically far lower than the normal 3x-5x-10x display tank size in GPH recommendations floating around.. I too throw out those numbers but usually state "the commonly accepted answer" or something to that effect..


Thats why to me you match skimmer performance and anything more is just a waste of energy..
Or whatever "filtration" you have down there..

Skimmer performance/processing rate should be fairly easy to calculate and usually known (all though the air injection does not allow one to use the pumps stated rate).
Flow rate through a canister or reactor is known (for the most part based on the pump used for it)

But I haven't seen any studies on the processing rate of macro algaes,etc.. they are likely out there I just haven't come across them easily yet..
IMO triton just pulled that 10x right out their butts.. 10x is cooler than 3-5x ;)

I’ve also got a large media box with 2 cups of carbon and about 4 inches of filter floss on top of it. It is right underneath my overflow so the water in the tank is dropped directly onto it.

Any thoughts as to if higher flow vs. lower flow would be better for that?

The difference as far as those is concerned is negligible..
Unless a toxin exists in the water then the faster you can mitigate it the better..

Faster flow through carbon will process more in less time but it will also exhaust the carbon faster..
Same with filter floss..

Thank you for stating this.
I've had discussions with alot of people about rules of thumbs (skimmer size, sump volume, gph, water change) and I always boil it down to: "Why do we take the actions and follow the methods we do?" I don't think it gets asked enough.

I'm in the 'turn the flow rate up until there is no more marginal benefit' camp because if I don't need to expend kW....

I've almost taken my sump offline because I run skimmerless but I realize my sump is filled with macroalgae and they work hard. My turnover is determined by my heater in the sump (2x the display).
My build in progress is just one display tank over another. The bottom one just happens to have more macroalgae. Everything that might be hidden in a sump wll be externalized including heaters, return pump and reactors. The return pump is DC as well so if I want to pump up flow for some reason (e.g. a quick water polishing), I can do so.

Just my 0.02.

There's very little science behind any of these claims. It usually come down to whatever a particular individual thinks is 'right'. In my view, turnover between the sump and tank must accomplish two things: ensure even heating (easy to verify) and effect proper surface skimming (not as easy to verify). I accomplish both by running about 3X. Everything else is immaterial.

Pretty much how the whole debate goes in everything I read. lol

True ....

I don't believe flow rate has much effect at all over how efficient the protein skimmer is.
Let's say you are sumpless and your skimmer is in your display tank... is that completely non-effective? Wouldn't that be a closer scenario to having a high flow through the sump vs a low flow?
Does it matter if the same water is possibly sucked through the skimmer multiple times while in the sump or wether it travels back to the display and then back to the sump before being processed again? Doubtful.

What you do want is enough flow in the tank to keep things stirred up and sent to the surface so it can make it's way to the overflow and down into the sump to be skimmed.
As long as that's happening, it doesn't matter.

Don't think anyone said that a system without a sump that has a skimmer is ineffective.. Of course its not..
Nor was there any real discussion of flow in the main tank..
This is all about flow rate through a sump..

My point was if we are just using energy just to circulate water down to the skimmer and back up if 90% of the water is being untreated thats inefficient.. and if we simply slowed the water down we increase the efficiency of the system as the water is being treated at the same rate (set by the skimmer) while using less energy to get the water there to be treated..
The treatment rate isn't changing but we aren't using more energy just to move water up/down untreated..

The efficiency of the skimmer isn't changing based on your return pump.. Its set by its own pump..
The efficiency of the entire system is increasing if you are closer to matching the treatment rate of your skimmer with your return pump..

The skimmer is most efficient the dirtier the water its in. The faster the flow through the sump the dirtier the water in the skimmer section will be. The question then is how fast does the skimmer remove proteins from the water and at 3x vs 5x vs 10x is there a significant difference in the protein content in the skimmer section at steady state. My guess is that it would be insignificant.

For me I like to run less water as it keeps the whole system less stressed so 3x is good for me and I just adjust the skimmer to get a good skimmate. Matching flow rates to me is a useless exercise.

I'm responding to the first post.
And then your first post, which talks about the flow through the sump being too fast to process. I call B.S. on that one. ;)

It's all one volume of water, whether it's split into two tanks or is just one tank. It will all process the same as long as water is actually getting sucked up into the skimmer.

I do agree that faster flow through the sump does not make the skimmer any more (or less) efficient, so yes, no reason to spend more energy (money) on faster flow. BUT, one may find other benefits to more flow through the sump besides water treatment.

Poor wording on my part..
Faster than it can process it "all" was my intention..

Just meant its moving faster that it can process the entire volume of water being transferred past..

I totally can see and understand the logic behind both low and high sump flow. What I have done on my setups for sump return pumps is to take the display gallons multiply by 10 and find a pump rated at about that gph range, then after head loss I figure I end up with around 5-7x turn over in the sump. This is what I have done and it has worked for me and this is for a sump located in a stand with under the 5ft head height. Obviously this would not work with a remote sump.

I'm totally with you - been arguing it for years. If matching flow rate to skimmer was important, recirculating units wouldn't work :lol:

And you 'know' these things, how? Or you just 'think' they are. I don't actually think either is true :)

This has long been my argument about why water flow through the sump has no relationship to the amount of water the skimmer can ingest. Even the best pass though skimmer does not skim all of the removable proteins in just a single pass (which is why recirculating skimmers exist). It's easy to observe that this is the case. Even if we could suspend fluid dynamics for a moment, and have 100% of the overflowed water run through the skimmer, the output water would still contain some removable proteins. Since we cannot suspend fluid dynamics, the reality is that some water in the sump never gets processed and some gets processed multiple times. I'd argue that at 10x the latter is less likely, but it still happens; so unless you believe that you skimmer magically removes everything in just one pass, that extra flow really gains you very little.

This seems obvious to me but maybe I'm missing something. For sure the skimmer is taking stuff out of the water and every system I've ever seen for cleaning and removing material from one place and moving it to another does so at a higher rate the higher the concentration of contaminants are. With no flow the protein skimmer would eventually scrub the skimmer section and there would be little to skim out. Poor efficiency.

At very high flow, the skimmer compartment is at the same contaminant level as the whole tank. So the only issue for the skimmer efficiency is whether the skimmer section has enough flow that the contaminant level isn't noticeably less than the rest of the system. I would bet it doesn't take much flow to accomplish that but I've never calculated what that rate would need to be.

Certainly the higher flow isn't going to hurt the skimmer and having a higher flow through the sump than the skimmer pump isn't an issue. It's not going to make the skimmer less efficient.