Square Skimmer

[andywg]

I am looking into setting up a marine pred system for a bunch of 6-9" preds that will encompass a tank around 150-165imp gallons (currently thinking of a 42x30x32H) plus around 50-70 imp gallons of sump.

Obviosuly, skimmers for this size tend to be large and very expensive. However, I have thought of making my own (After all, I will be making almost all the LR in the tank myself, why not the skimmer?). The cost of acrylic, or wide PVC, is putting a dampner on this.

Then someone suggested a square skimmer made of glass.

I can get the glass cut more than easy enough, and having made tanks and trickle towers that should not be a problem. Also, the flat sides would allow for a far better join of bulkheads to connect piping.

Obviously there will be some loss of performance as the corners would allow some dead zones of reduced flow, but if the thing is large enough, and has aenough circulation and air in it, this should work out ok, yes? I would use a venturi air injection throught he use of a couple of eheim 1260s as recirculating pumps (main system pump would be a Sequence 10,000 pumping over 9,500 LPH for only 95W).

I guess I am basically looking to see if there is any catastrophic reason why I should not do this. Also, could I just use two Sequence 10,000s and have one more for circulation in the tank, and one more for the sump return and skimmer (I seem to recall reading that sumps do not need a huge flow through them).

Any thoughts people?

Cheers

Andy

 

[SkiFletch]

Well, without knowing the engineering challenges myself... I'd say BIG pump and LOTS of air. Might work, might not. A key for SURE will be to design your inlet to the skimmer that it comes in and points to a right angle directly to simulate turbulent flow inside the skimmer. pointing it straight at the opposite square wall will probably not be good for bubble fractionation and mixing.

 

[andywg]

Thu huge Deltecs for shops seem to rely on 2 or 3 eheim 1260s with a normal 6mm airline on for recirculation and air flow. I make that around the 6,500 LPH mark. I doubt I would want quite that much, so around 5,000 LPH for the recirculation and then 4,500 LPH for pumping into the skimmer should be enough.

I hear what you are saying on the inlet, though my aim would be to have a couple of "closed loops" so that the pump sucks half of its water from the skimmer and half from the sump. This would then allow for around 3 outlets, all with venturi on.

 

[SkiFletch]

Interesting concept on the closed loop... slight overengineering but should work

 

[andywg]

One of the more important factors when designing a skimmer is the "contact time" that the water is in contact with the bubbles. Re-circulating helps lengthen this time by taking water from the bottom of the skimmer (that would soon be about to leave the cylinder) and putting it back at the top.

If I had a large flowrate going into the skimmer then a lot of the water could just flow straight through, doing it this way allows for the water to spend more time in the skimmer.

I guess the real trick will be in how to get the airline onto the piping in a safe way that prevents any chance of it failing.

I suppose I could plumb in a T piece and then reduce the pipe from the tee and run the pipe up far enough that it just sucks air in that way...

 

[SkiFletch]

I suppose I could plumb in a T piece and then reduce the pipe from the tee and run the pipe up far enough that it just sucks air in that way...

That's totally the right way to do it... Keep it simple

 

[Matthew5664]

Could drill a 5mm hole and solvent weld a 6mm air line straight conector in.

As for the rest of it the only problem I could see is the dead zones you talked about. However I have a cunning plan. Using two recirculating pumps with venturis on opposing sides of the skimmer with 45degs conectors on the inside wouldss help eliminate these. as for the output of the pumps this would not matter as they are only recirculating the water in the skimmer the troble comes with the input pump. Too fast and all the bubbles get sucked out too slow and you only use half the body of the skimmer for dwell time. To allow for this you could use a powerfull input pump with a bypass through a ball vale to the sump. This way you can regulate the flow through the skimmer without hurting the pump. If this is all to fuzzeling for the brain I would be happy to draw you up some plans?

Hope this helped.

 

[andywg]

I will use one large pump for both recirc and power. The wattage of most pumps is so bad it's not funny.

I have an eheim that pushes 3,600LPH at 80W, the Sequence 10000 I have planned pushes 9,500LPH for 95W. However, I plan on splitting the inlets and outlets into 3 so that two inlets to the pump will come from the skimmer and one from the sump and the outlets can all be placed into the skimmer I would be trying to have all three (or possibly 4 so that I can point in all directions at once) with elbows pointing somewhat down and somewhat towards the corners but after pushing throught he centre. Through the use of ball valves I can ensure that most of the water into that pump will come from the skimmer and not the sump.

My main aim is to obliterate the worst of the dead spots through the use of large circulation of the water. I don't see there being too much flow as I was looking at larger skimmers by deltec and they have extremely beefy recirc pumps (one has 4 eheim 1060s each pushing 2,200 LPH purely for recirc and venturi). Considering this will be a larger marine pred tank the skimmer will take a far more prominant role than it would in a reef tank. I will be growing very few, if any corals and inverts, so I have no nutrient levels to worry about. I aim to create a skimmer that in a reef setup could handle around 500 gallons of water so as that I am 2.5 times overskimmed (and if I can get it larger, so much the better). I don't think an actual through flow of 3,000 to 5,000 LPH on a skimmer for a 200 gallon setup will be too quick.

My fear with drilling and then solvent welding is that the circular pipe may not form a good surface to weld onto, the pipe is not very thick, and I have seen first hand the floods that can be caused by less than perfect joinings of pipes. I have tried solvent welding airline connecters to drinks bottle lids (for DIY CO2 in FW) and had very mixed success. I would definately not trust this in a large setup with huge amounts of water going through.

I wonder if it would massively detract from the venturi effectiveness if the air inlet was wider. Anyone have any knowledge of this?

 

[andywg]

Hmm, it appears that extremely large (multiples of thousands of gallons) setups will often have square skimmers and these outperform the round ones. So my idea isn't entirely stupid, just that it is easier to create more turbulence in a cicular one.