What does depth of water do for skimmers?

[Rhodes19]

Hi All,

Now that I have a big boy skimmer (SWC 200) for my 180, I have become aware that I don't know everything about skimmers.

What does the depth of water the skimmer sits in have to do with proper/optimal skimmer operations? And, how do you determine the optimal depth for the skimmer? I'm thinking the depth has to do with the water level in the chamber. Not so much to do with the power of the pump as it does with the water pressure on the out let (skimmer sits higher = less pressure, skimmer sits lower = more pressure). But if you can regulate the amount of water in the chamber by adjusting the out let tube/gate valve, does the depth the skimmer sit in really matter?

Any way, if anyone can explain it to me I would greatly appreciate it. Thanks.

Chris

 

[JulesVane]

Excellent question...I'm following along...

 

[SubRosa]

Contact time between air and water. The longer the bubbles have to travel to get out the top the more scum they lock up and take with them.

 

[steved13]

You're close...It's not the water pressure on the outlet...it's the starting water level in the skimmer. If it's sitting in 8 inches of water you're starting with a 8 inch water level inside the skimmer so the pump has to increase the level the rest of the way. The way my skimmer works, and I believe your skimmer works the same way (but I'm just going by a picture)Once the starting level is fixed you adjust the output restriction to fine tune the internal level. Usually you start with it at the bottom of the neck and let the foam rise from there, and fine tune it for dryer or wetter foam.

The manufacturer recommends between 8" and 10" for that skimmer.

I hope this helps.

 

[Rhodes19]

Contact time between air and water. The longer the bubbles have to travel to get out the top the more scum they lock up and take with them.

Hi SubRosa,

Thanks. Yeah, I understand that part but what I want to know is how does the depth the skimmer has to sit in effect skimmer operations? For example, what is the difference in operations if the skimmer sits in 10" of water vs. sitting in 4" of water? What is the proper depth (given my the manufacture) and why is it the proper depth? Why does that depth make the skimmer work optimally?

 

[Rhodes19]

You're close...It's not the water pressure on the outlet...it's the starting water level in the skimmer. If it's sitting in 8 inches of water you're starting with a 8 inch water level inside the skimmer so the pump has to increase the level the rest of the way. The way my skimmer works, and I believe your skimmer works the same way (but I'm just going by a picture)Once the starting level is fixed you adjust the output restriction to fine tune the internal level. Usually you start with it at the bottom of the neck and let the foam rise from there, and fine tune it for dryer or wetter foam.

The manufacturer recommends between 8" and 10" for that skimmer.

I hope this helps.

Hi steved,

Thanks for the info. So the initial water level has to do more with how much the pump has to work to get the level where you want it? Or I guess in other words, how much power your pump has? If I had a stronger pump would that allow me to raise the skimmer higher out of the water and give me more bubble contact? Just trying to figure out the mechanics behind it.

 

[seabass]

Hi Chris!!When I got mine I already had my sump at 11 inches which wasn't going to work with this badboy so i built a stand which had it at 8 inches and i was wondering the same thing.Would it work better on the 10 inch side so i cut my legs and dropped it down to 9 1/2 inches and really didnt see any difference.I understand what your asking and it is a excellent question i'm sure alot of people are reading along for the answer.Including me lol.Here is a pic of mine.Nice brown scum.

 

[tnwillia]

I'm no help, I found with my SWC putting it in 14" of water (making a fuge think it was a sump) I got no bubble production. When I raised it in that 14" to equal their recommended 9" (from the base) I got great bubble production. I never understood this but it worked.

 

[steved13]

It's not just the strength of the pump. It's a balance. Your pump is flowing water and adding fine air bubbles. The whole idea is contact of air and water, finer bubbles = more surface area = more air water contact area. If you raise the skimmer your taking some water out of the equation, using a stronger pump may make up the difference but it may( probably will) add more air and you still won't have enough water, so you're back where you started with the water level. Also, to large of a pump may force the water through to fast and reduce the contact time, making the skimmer work poorly. To much water not enough bubbles, bubbles pop at the surface no foam. Not enough water to much air and the bubbles foam but can't travel far enough to the collection cup some pop and return the skimmate to the system very liitle to none make it to the cup for removal.

Are you running into a depth issue or just curious? If it's a depth issue give us some info and we can put our heads together and try to come up with a solution.

 

[Gfoot2000]

between the airline to your pump, you don't want water level too high or it'll be harder to suck air into the pump like what tnwillia mentioned with his 14 inches depth,

 

[Rhodes19]

Hi Chris!!When I got mine I already had my sump at 11 inches which wasn't going to work with this badboy so i built a stand which had it at 8 inches and i was wondering the same thing.Would it work better on the 10 inch side so i cut my legs and dropped it down to 9 1/2 inches and really didnt see any difference.I understand what your asking and it is a excellent question i'm sure alot of people are reading along for the answer.Including me lol.Here is a pic of mine.Nice brown scum.

Hi seabass,

Nice picture. I need to take a picture of mine and post it. I have a few friends hounding for some up dated pics. Right now I have mine set in 10" of water. I may play with it over the weekend and see what happens if I get a chance.

 

[Rhodes19]

I'm no help, I found with my SWC putting it in 14" of water (making a fuge think it was a sump) I got no bubble production. When I raised it in that 14" to equal their recommended 9" (from the base) I got great bubble production. I never understood this but it worked.

Hi Tom,

Thanks. I'll have to raise it up and see what happens. I know if I have it too shallow, it will lean/fall over because it's top heavy. I'm using an old 55 g tank as a sump/fuge. Well, sump anyway. I got rid of my cheato because I didn't see any change in nitrates plus, the cpf was causing algae and cyano growth in the sump. It seems to have reduced since I got the skimmer running and the light is no longer on.

 

[Rhodes19]

It's not just the strength of the pump. It's a balance. Your pump is flowing water and adding fine air bubbles. The whole idea is contact of air and water, finer bubbles = more surface area = more air water contact area. If you raise the skimmer your taking some water out of the equation, using a stronger pump may make up the difference but it may( probably will) add more air and you still won't have enough water, so you're back where you started with the water level. Also, to large of a pump may force the water through to fast and reduce the contact time, making the skimmer work poorly. To much water not enough bubbles, bubbles pop at the surface no foam. Not enough water to much air and the bubbles foam but can't travel far enough to the collection cup some pop and return the skimmate to the system very liitle to none make it to the cup for removal.

Are you running into a depth issue or just curious? If it's a depth issue give us some info and we can put our heads together and try to come up with a solution.

Hi steved,

Thanks. No its not a depth issue. I have it in 10" of water per the manufacturer's recommendation. I'm just curious on why and how it works. I know I need good contact time but I'm trying to figure out how the water level fits into the equation. I know if I want to raise the water level in the chamber all I have to do is restrict the out flow or if I want to lower the water level in the chamber is to open up the over flow.

 

[Rhodes19]

between the airline to your pump, you don't want water level too high or it'll be harder to suck air into the pump like what tnwillia mentioned with his 14 inches depth,

Hi Gfoot,

Thanks. I didn't think of that. Is that because of an increase in atmospheric pressure (used to be a diver) on the pump or does that have to do with the efficiency of the air injector/venture?

 

[JulesVane]

As this is an excellent question, I feel I (we) still don't have an (the) answer. We all understand the water level balance INSIDE the skimmer. But, what is the difference if the skimmer SITS in 6" of water or 10" of water? Not inside the skimmer, but surrounding the skimmers body in the sump. Maybe I'm missing something...

 

[steved13]

Not inside the skimmer, but surrounding the skimmers body in the sump. Maybe I'm missing something...

The level "surrounding the skimmers body in the sump" IS the starting level inside the skimmer?

As soon as you put the skimmer into the sump it fills to the level of the sump. When you raise the level in the sump the skimmer overflows...not because the pump got any stronger but because the starting level was raised.

 

[steved13]

Hi steved,

I know if I want to raise the water level in the chamber all I have to do is restrict the out flow or if I want to lower the water level in the chamber is to open up the over flow.

Correct that is how you fine tune it...by adjusting the output. But to further clarify the answer to your original question...if your sump level is to high, no matter how far you open the output, it will still overflow. If it's to low you could probably close it enough to get some action but then the flow would be so low you wouldn't be skimming enough of the system to make a difference.

 

[Rhodes19]

Correct that is how you fine tune it...by adjusting the output. But to further clarify the answer to your original question...if your sump level is to high, no matter how far you open the output, it will still overflow. If it's to low you could probably close it enough to get some action but then the flow would be so low you wouldn't be skimming enough of the system to make a difference.

Hi steved,

Ok, I think I got it. Because the pump is not strong enough to raise the water level to the proper height for skimming, we have to sink the skimmer to reduce the difference between what the water level that needs to be in the chamber for it to skim properly to the water level in the sump (less pressure on the pump). So basically, the proper depth for a skimmer comes down to the pump parameters/operations. I can see that.

 

[steved13]

Well, I'm not really comfortable with your characterization of the "pump is not strong enough", in a eall designed skimmer the pump is just as strong as it needs to be, much stronger or weaker it won't work properly. Plus remember the pump actually is strong enough but since most of it's job is to input air, it's not pumping all water. Try putting your finger over the air intake and watch how fast it fills with water.

It sounds like you've got the idea.

 

[nanoskim]

I'm no help, I found with my SWC putting it in 14" of water (making a fuge think it was a sump) I got no bubble production. When I raised it in that 14" to equal their recommended 9" (from the base) I got great bubble production. I never understood this but it worked.

Very simple...the higher the water level above the pump, the harder it is for the air to be sucked in by the venturie (atmospheric pressure vs water depth pressure on the pomp)...at one point you will just get water movement.

There are a lot of physical and chemical parameters involved in designing an efficient skimmer...about 12 that I have identified so far.

Hope this helps.