Gravity fed skimmer?

[pottsburg]

I want to have my skimmer gravity fed by the overflow box so that I can cut down on electricity/heat with the tank. This isn't about if it will make a difference, this is about how to do it lol.

I've got a coralife skimmer that is rated at 325gph. I'm expecting that my overflow is moving between 300-400gph down the tubes. Do I need to do anything besides stick a T with a ball valve on my overflow hose and run it into the skimmer? I had thought that with water evaporating, it might alter the GPH moving, but if my sump moves down an inch and the pump is still pushing the same amount of water up, then water level shouldn't affect the flow going through the overflow, should it?

thanks ahead of time!

[Keelay]

When I put together my first skimmer design it was completely gravity driven from the overflow - just like you are trying to do. It didn't work that well. I have a 100 Gallon tank, and it didn't generate enough bubbles to skim very well. I think this would have worked fine on a 30 gallon or so. Or if you're not looking for super skimming.

It's not about flow so much as pressure although you need to regulate the flow as well. To make a venturi of any type work you need pressure. This is what generates the suction of air into the water column. Sure you can guarantee that all the water the return pump pushes will go though the skimmer, but this doesn't mean you can create a lot of bubbles with it.

Gravity creates water pressure as you go deeper in any column of water. Actually .44 PSI per foot depth. So take your typical 5' aquarium. That is a potential 2.2 PSI of pressure. Since the venturi won't likely sit on the very bottom, you might have 4.5' = 2.0 PSI. That isn't much to work with in terms of pulling a lot of air. Compare with a MAG 5 pushes 4.6 PSI.

I have since modified it to make it gravity assisted (http://www.members.cox.net/kyledugger/reef/DIY_gravityassistpump.htm) to keep with accomplishing the same goal of reducing electricity. I am able to get more performance out of a lower wattage pump. This works phenomenally.

[Keelay]

You will also want to regulate the skimmer flow. The return pump will vary flow rate over time. This is especially true if you have a prefilter. As it clogs, or as gunk builds up in the impeller chamber, the return pump slows down. You would like to regulate the water flow into the skimmer.

This is easy to do if you have two drains in the overflow. Make one stand pipe lower without a durso and add a valve. Make the other a durso. See picture. Just ignore the pump and float switch setup - you're looking to do this without the pump.
http://www.members.cox.net/kyledugger/reef/images/systemsetupsimple.gif

When you set the valve so allow lets say 300 GPH through it and your pushing 350-400 with the return. So we are saying it varies 50 GPH between prefilter cleanings. This will shield the skimmer operation from these variances. The water column in the overflow will stay at the durso inlet height, providing constant pressure to the
air injection method of your choice. It also therefore provides constant flow as well. The extra "varying" flow will go down the durso (50-100GPH).

This will make the skimmer more of a set and forget setup. You won't have to adjust it as the return pump changes it's behavior etc. I've been pleased with mine.

[RandyStacyE]

This topic can be real complex or super simple.

Your skimmer should be fed approx 1.5 - 2 times your total system volume per hour.

What is your total system volume?

Your return pump should be putting out WELL OVER 1.5 – 2 times your total system volume per hour. If it is not, I assume that you are relying on power heads or closed loops for circulation in the display tank. To make this super simple … all you would need to do is rob 1.5 – 2 times total system volume per hour directly from your overflow, but in order to do this your return pump must be putting out more than this rate of flow.

I’ve been doing it THIS WAY (http://www.randystacye.com/feedingskimmer.htm) for over about a couple months now.

Another way to feed your skimmer would be by tapping into your return line, but keep in mind that by doing it this way you would be robbing flow to your display tank.

The simplest way to be to just use a feed pump. You could even use a NW/mesh mod pump for even more air!

[hogben]

For a 46 gallon tank you only need to be feeding the skimmer about 90gph which you can do from a T off the overflow and a ball valve.

Here is a lot of info and pics of feeding skimmers from the overflow when I asked:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=1088553

[pottsburg]

I've got a 46 bowfront with a 20 gallon fuge below. My return pump is a QuietOne (from petsmart; i know, i know) but it should be pushing somewhere int he ballpark of 300gph. The skimmer I've got has a little pump that says pumps up to 325gph. Should I run the drainline from the overflow straight to the skimmer with a T in the line and have a drain hose running off the T, so that most of the water runs straight to the skimmer? I'll put a ball valve in there before the skimmer to regulate flow of course. As for getting bubbles out of it, it's got an air line running off of it that sucks the air into it, so w/ 300gph coming down and getting air, it should operate fine, right?


The only way that the flow to the skimmer would change would be if the return pump were to change, correct? Evaporation wouldn't effect it?

[stugray]

I have a 125 Gal dual mega flow AGA tank.

My sump is in the basement. One of my overflows goes straight into my 5 gallon bucket skimmer and a hartford loop dumps the skimmer to the sump. However, my skimmer is a recirculating beckett so I dont rely on the head pressure from the display to actually drive the skimmer. I tried that with my EV-120, and it wasnt consistent enough. My total sytem volume is about 200 Gal, and a AGA megaflow is rated at about 500-600 GPH but I am guessing more like 400.

So, I should be right in the sweet spot ( 1.5 -2 times ) as Randy mentions above.

HTH

Stu

[hogben]

<a href=showthread.php?s=&postid=9709773#post9709773 target=_blank>Originally posted</a> by pottsburg
The only way that the flow to the skimmer would change would be if the return pump were to change, correct? Evaporation wouldn't effect it?

Evaporation shouldnt effect it.

So how do you actually plan to plumb the feed into the skimmer. You can see on many recirculating skimmers they have a feed connection in the upper half of the tower. Does your skimmer have one or do you plan to DIY?

[pottsburg]

I'll just fit a hose to go from the drain, at the T, to the skimmer.

It's a plain old skimmer, is there a bid difference between a coralife skimme and a recirc skimmer??

[hogben]

Well like see on this octopus right above the pump is a connection to the skimmer body for a feed:

http://www.aquacave.com/images/Skimmer%20DNW-110%201.jpg

What you wouldnt want to do is connect it directly to the intake of the skimmer pump, depending on the flow from the overflow it could cause the pump to cavitate.

There is a way to do it correctly if your skimmer is not recirculating, I dont think the coralife is. I'll try to find the picture I saw.

[pottsburg]

cavitate? because of too much air going into it??

[hogben]

They cavitate when the input is restricted and it cant get enough water.

Here is how he plumbed it to feed from the overflow:

<a href=http://reefcentral.com/forums/showthread.php?s=&threadid=898776&perpage=25&pagenumber=15 target=_blank>Originally posted</a> by Roland Jacques
Direct feed for a insump skimmer, (for people who dont want to do recirc mods)

Their a number of ways to do this heres a good one IMO.
Hope you can make this out . It works good for me when feeding a insump skimmer.

Tank overflow water goes in at the bottom, up the 1 1/2" pipe too the "Y" fitting. Most the water goes down the wye reduced to 3/4" pipe, then a ball valve, then to a tee attached to the venturi.

Adjust the valve so that no bubble are coming out the tee, then you just turn on your skimmer.

http://reefcentral.com/gallery/data/500/26018P1060028.JPG
http://reefcentral.com/gallery/data/500/26018P1060040.JPG

So its bascially the same thing except a T on the skimmer pump intake so that if not enough water is coming down the drain it can pull from the sump as well. Thats how I understood it.

[pottsburg]

okay. My skimmer is not recirculating, but why does it need to be if I still have water running into it at a good pace?

[pottsburg]

I got it, so put a gate valve on the outlet of the skimmer so that it reduces flow without cavitating. do I need to have a vent on it as well to keep too much air from going in?

If I'm doing this the way I think, it will have absolutely no pump on it, for water being pushed through or for recirculation.

[jmuscat2]

Just make your skimmer a recirculating type. It is an easy mod and it will increase your pump efficiency. Then just feed the skimmer with the overflow and control the water height in the skimmer with a gate valve mod.

[pottsburg]

so with a recirc mod, im still using a pump, why is it worth doing then?

[jmuscat2]

you'll never get enough pressure with just gravity to operate a skimmer IMO. You can use gravity to feed the skimmer but you need the needle wheel or mesh modded pump to get enough bubbles into the skimmer.

[skydvr]

I'm planning on building a counter current skimmer and was considering gravity feeding it.

Only problem is figuring out how much flow is actually going thru it. It will require about 50gph to get the proper 2x tank volume per day turnover rate in my 72. I was thinking I could probably calculate pipe size to regulate flow.

Other concern would be controlling backpressure on the outlet to make sure the level in the skimmer is maintained. not enough, the skimmer drains. Too much and not enough flow thru the skimmer and the collection cup would flood, making a mess on the floor.

I think tapping into the side of the sump (the skimmer won't fit under the stand) will provide enough backpressure to prevent excessive draining without causing flooding.

[Keelay]

<a href=showthread.php?s=&postid=9712276#post9712276 target=_blank>Originally posted</a> by skydvr
I'm planning on building a counter current skimmer and was considering gravity feeding it.

Only problem is figuring out how much flow is actually going thru it. It will require about 50gph to get the proper 2x tank volume per day turnover rate in my 72. I was thinking I could probably calculate pipe size to regulate flow.

Other concern would be controlling backpressure on the outlet to make sure the level in the skimmer is maintained. not enough, the skimmer drains. Too much and not enough flow thru the skimmer and the collection cup would flood, making a mess on the floor.

I think tapping into the side of the sump (the skimmer won't fit under the stand) will provide enough backpressure to prevent excessive draining without causing flooding.

Use a gate value on the outlet pipe. Dial in as much back pressure as you need.

[Keelay]

<a href=showthread.php?s=&postid=9712079#post9712079 target=_blank>Originally posted</a> by jmuscat2
you'll never get enough pressure with just gravity to operate a skimmer IMO. You can use gravity to feed the skimmer but you need the needle wheel or mesh modded pump to get enough bubbles into the skimmer.

I actually don't agree. I think it is possible. I didn't know he had a 46 gallon. You might get by with running it this way. In my experience. If you have something like a 5' drop from overflow to skimmer venturi you can generate enough bubbles to skim a smaller aquarium. The key will be the right venturi. If only they made a miniature beckett jet, that would be perfect. the larger ones wont do for this much flow/pressure. I was using spray injection at the time for mine.

[allykahn]

Is it ok to jump in? I have a few questions.

I have a 180g w/40L sump. I see from the pics that I can use 1 drain to supply the skimmer.

1. Will this be enough flow for the skimmer?
2. What about the other drain?
3. Are recircs only external?

[Keelay]

<a href=showthread.php?s=&postid=9720139#post9720139 target=_blank>Originally posted</a> by allykahn
Is it ok to jump in? I have a few questions.

I have a 180g w/40L sump. I see from the pics that I can use 1 drain to supply the skimmer.
1. Will this be enough flow for the skimmer?

2x flow through the skimmer is 360gph. 1" pipe will support up to 600gph. I think that you are fine

2. What about the other drain?

The other drain is used to regulate the water flow through the skimmer drain. That means the skimmer drain gets a fixed flow rate. An the extra drain takes up the variance.

3. Are recircs only external?
No, you can implement an internal recirculation skimmer.

[allykahn]

The other drain is used to regulate the water flow through the skimmer drain. That means the skimmer drain gets a fixed flow rate. An the extra drain takes up the variance.


Not sure if I understand this. I may need a visual.

My sump setup is skimmer/return/refugium. As of now, both overflows drain into the sump. With a RC skimmer, I could use a pump (360gph or so) to feed the skimmer from the sump or use 1 drain to feed the skimmer directly.

If I use the one drain for a direct feed, the water from the other overflow drain does not get skimmed and flows through to the return.

I'm trying to decide if I need to get a recirc or in-sump to replace the skimmer that I have.

Thanks

[RandyStacyE]

Some people simply dump their overflow right into the sump. In such a case, one can use any type of skimmer they want. Some prefer to feed their skimmer from their overflow BECAUSE that water contains 'scum' that typically floats on top of the water in their display tank.

Feeding a skimmer from the overflow is not necessary at all, but could be considered as 'ideal' since it will direct this 'scum' right into the skimmer to be skimmed.

A recirc skimmer is a VERY good candidate to be easily fed from any overflow. Many people feed their RC skimmers differently. Some simply use a small pump to suck water out of the sump and shoot it into the skimmer. Some use a small needle wheel/mesh mod pump (for more air and better control of the gph flow). Sucking water out of the sump to feed the skimmer will not pick up the display tanks’ ‘surface film’ as effectively as it would if the skimmer were gravity fed.

Allykahn, you should post a pic of your skimmer, maybe you can just modify the one you have.

[allykahn]

It is an ASM G3. I have read a few posts about modding it but even with that, I did not think it would still be enough for my bioload.

[hogben]

<a href=showthread.php?s=&postid=9711764#post9711764 target=_blank>Originally posted</a> by pottsburg
so with a recirc mod, im still using a pump, why is it worth doing then?

Gravity fed and gravity powered are very different terms. My fault for misunderstanding. Like many of the above posters have said I think there will be difficulties in trying to power your skimmer from the overflow drain.

If you want to modify your skimmer to be fed dirty water from the overflow but still be powered by a pump, thats a different conversation, but not one youre interested in. :D

[Lubu]

How about the AquaC Remora pro? If you connect the intake of the remora with your overflow box it may work pretty well.

[Keelay]

The other drain is used to regulate the water flow through the skimmer drain. That means the skimmer drain gets a fixed flow rate. An the extra drain takes up the variance.

If you are looking to power the skimmer bubble generation with the water from an overflow. The things you want are:

1) A fixed water height in the overflow. Changes in the amount of water the return pump feeds should not fluctuate the water level.

2) The pipe feeding the venturi, spray injector, beckett (or whatever bubble generation means you are trying) must be totally full of water.

3) You want a fixed flow rate through the skimmer feed pipe.

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You want 1 since this provides a constant pressure. This way bubble generation will be consistent and will contribute to a set and forget skimmer. Any other type of skimmer is a PIA.

You want 2 since if it's not full you aren't using the column of water to generate any pressure(you basically negate the meaning of #1). If you have a single drain in an overflow you do not satisfy #2. In fact the pipe is mostly full of air most of the time and provides no pressure on the bubble generator. Well I guess because of the constriction the water will back up some and create pressure, but you loose control over the water level of the backup.

You want 3 for that set and forget skimmer. Adding more and then less flow will cause the skimmer water column to vary in height making your skimmer hard to tune and require frequent tuning. Back to PIA.


Note it is important to remember that the flow rate of your return pump will vary. This is especially true if it has a foam prefilter. It will slowly clog causing less flow rate. The impeller will slowly gunk up and will slow the flow rate. Because of this we shouldn't depend on the flow rate of the return pump to be constant and therefore provide a good feed to the skimmer. The dual drain skimmer removes the return pump fluctuation from the skimmer operation.
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Having two drains in one overflow allows you to do just that. Have one drain a durso and the other an open ended standpipe. The open ended standpipe should be shorter by a few inches. The spray injector or a valve before the injector will control flow through the shorter stand pipe. Set it so that the water starts to go down the durso a little.

At this setting if the water flow rate coming into the overflow compartment varies, the excess will go down the durso drain. The water height in the overflow compartment stays constant satisfying #1. The constriction on the valve or venturi (bubble generator) will satisfy #2 & #3.