Enhanced Sump Design - Baffle Configuration

[abcha0s]

We've been experimenting with a slight variation on the way in which traditional baffles are installed in a sump. I have a theory as to how they work, but wanted to hear what others think of the idea. If it's generally accepted as a "good idea", we will probably incorporate it into all our builds - if not as a standard feature, at least as an option.

Here's a traditional baffle design:



The third baffle will always sets the water level. With the first baffle set at the same height, there is only a thin layer of water going over the top. This creates a strong undertow as the water concentrates and is then forced downward. This current can (and does) pull micro bubbles with it. There is also a small residual current that travels back potentially pushing micro bubbles into the downward current.

Here's a modified baffle design:



The idea behind a shorter baffle is to allow the micro bubbles to collect on the surface and to create a gentle downward current so that the force is insufficient to pull the bubbles along with it. A wider flow produces a weaker current.

Here's how this might look:



In many of our sump designs, the water does not follow a standard end-to-end flow. This sometimes means that the channels are narrow thus increasing the velocity of water flow.

Any thoughts? Does the theory hold up?

- Brad

[banditpowdercoat]

That is how I make my sumps too The thinking is correct. The 1st baffle being shorter so the water doesnt 'tumble' over it and add more bubbles. Working great for me as I have a lot of bubble entering my 1st sump chamber, but none get past the baffles

[reefwars]

ive always been curious and i could be wayyyy off here but if you were to take your first baffle and create knotched teeth kinda like an overflow has with maybe 1/8" spacing between knotches ,would the small spacing help in bursting or dissapating the small bubbles?? or would it create more bubbles??

was just curious as ive thought about doing it before but never ever tried it

[banditpowdercoat]

If there is no waterfall through the teeth, then it wouldnt create more bubbles. But breaking them up, no. If the bubble is under the water, nothing other than it coming to the surface, will get rid of it. Larger bubbles rise and 'pop' faster than tiny bubble. Tiny bubbles can be carried down with the current much easier. That's why Microbubbles can fill a tank so easy. So, if the teeth were to chop up the larger bubbles into smaller ones, then in effect, it would make it worse.

[mark]

might expect the extra turbulance in the first drawing would help microbubbles being driven out and also increase aeration of the water. Really though don't think there would be a huge advanage of one over the other.

[Lampshade]

I have that setup right now in my sump. I needed to raise the water level in my skimmer chamber a bit, so i added an extra 3/4" to the last baffle. You are very right with no turbulance in the first chamber, seemed like a good idea, didn't notice a change because i had no bubbles before and none after. When i had low flow it worked great, I now have 2500+gph going there, and have micro bubbles everywhere... but no hair algae.

If you have the water level close to that height in the return chamber then the raised baffle is great, mine lifted the flowing water another 3/4", creating more waterfall, creating more bubbles. If you had another "down" baffle you could get rid of this. It's what i plan on doing shortly, but need to figure out how small to make it so that it's functional

[lastlight]

Brad I like that idea. I think the downward suction is also due to the distance between baffles 1 and 2. The area of that gap determines what sort of pressure is created there I think. I'd use a greater distance between 1 and 2 and then experiment with lowering baffle 1. I think the horizontal distance will have more effect. As it is you are letting the bubbles get farther away from the surface as well so in my opinion a combination might be more effective.

[Skimmerking]

i ran my baffles the other way Brad. I went for length in stead of up and down. I get alot more crap building up too and its easier for me to clean.

[RedCoralEdmonton]

Im no sump builder, but Id have to agree with Lastlight, making the baffles farther apart will slow the velocity...

Steve

[abcha0s]

Wow. Awesome feedback guys. Thank you.

Dan - I think your right about the effect the teeth would have. As you suggest, micro bubbles are hard to deal with because they rise very slowly.

Originally Posted by Lampshade

If you have the water level close to that height in the return chamber then the raised baffle is great, mine lifted the flowing water another 3/4", creating more waterfall, creating more bubbles. If you had another "down" baffle you could get rid of this. It's what i plan on doing shortly, but need to figure out how small to make it so that it's functional

Lot's of good information here. I will elaborate on this in my clarifications below. I do have one question though...

Wouldn't the water level in the return chamber be set by the placement of your ATO level sensor? - To avoid this, the sensor for my ATO is about 1/3" above the baffle hieght. I get some ripples over the 3rd baffle, but no downward current.

Originally Posted by lastlight

Brad I like that idea. I think the downward suction is also due to the distance between baffles 1 and 2. The area of that gap determines what sort of pressure is created there I think. I'd use a greater distance between 1 and 2 and then experiment with lowering baffle 1. I think the horizontal distance will have more effect. As it is you are letting the bubbles get farther away from the surface as well so in my opinion a combination might be more effective.

Brett - You're right. The height of the 1st baffle is only half of the story. The distance between baffles is also a factor. However, in most sump builds, the distance between the baffles is already sufficient (generally between an 1" and 1.5"). This depends on the rate of flow of course.

Originally Posted by asmodeus

i ran my baffles the other way Brad. I went for length in stead of up and down. I get alot more crap building up too and its easier for me to clean.

Hi Mike - If you have the space, your approach works well. The challange is that our sump designs are often space limited. It's a bit of a game to see how much functional space we can fit inside. The result is often a narrow baffle section.

Let's work the same design but with the new ideas being discussed:

The first thing that we need to consider is the effect of "gph" through the sump. It stands to reason that the perfect baffle height and distance between baffles could only really be determined if the exact gph was know before designing the sump. It's easy to imagine that if only 10 gph was moved through the sump, this whole exercise would be moot.

Consider a traditional sump design (same height baffles) with 3000gph moving through it:



In this configuration, the water level will rise considerably above the height of the baffle. The downward force will be substantial.

Now consider that only 2000gph is moving through the sump:



... and finally, consider 1000gph moving through the sump:



As the gph decreases, the water level will also decrease. At 10 gph the water level may only be 1mm above the baffle.

In consideration of Brett's point, let's move the 1st and 2nd baffles closer together:



The water level will rise and the downward force will increase. However, the height of water above the third baffle will remain unchanged.

The perfect design - IMHO

First, you must know the height of point A. This is purely a factor of gph.



The measurement for distance B requires a little bit of guess work. It is also a factor of how wide the baffle section is. I would speculate that for most sumps a measurement of 1" or 1.5" would be sufficient. You could work this distance out experimentally by positioning a fourth baffle to the right of the 3rd baffle. With the sump running, move this fourth baffle closer to the 3rd baffle until the water level starts to rise. The point just before the water level rises is the ideal distance at point B.

B - A = C and is the height by which the 1st and 3rd baffles should differ.

The measurement for distance D is the optimal height at which to place the ATO level sensor if the intent is to minimize micro bubbles.

Note: The only problem with keeping the water level so high in the return section is that a protein film can build up on the surface. A little bit of a water fall and some agitation might not be a bad idea.

- Brad