Spray bar with 2 canister filters? - Page 2 - The Planted Tank Forum
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post #16 of 19 (permalink) Old 04-04-2010, 08:04 PM Thread Starter
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WOW! Guess I should have paid attention in physics class!
Thank you wkndracer, you gave me a clear and easy to understand answer. Does what Landau said make a significant difference? Will drag effect the flow that much? I cant imagine making the holes smaller then 1/8". If I wanted to start off with less, could I do a 1/8" hole, every 1" instead of every 1/2"? Help me out guys! I'm drowning in mathmatics!!
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post #17 of 19 (permalink) Old 04-05-2010, 12:41 AM
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Quote:
Originally Posted by Guns286 View Post
WOW! Guess I should have paid attention in physics class!
Thank you wkndracer, you gave me a clear and easy to understand answer. Does what Landau said make a significant difference? Will drag effect the flow that much? I cant imagine making the holes smaller then 1/8". If I wanted to start off with less, could I do a 1/8" hole, every 1" instead of every 1/2"? Help me out guys! I'm drowning in mathematics!!
Actually what he posted was you may need larger holes then 1/8" and yes what he said makes sense but at an engineering level. I work in a dual 750 megawatt power plant with steam boilers. Boundary layer effect is why the inside of the tubes in the water walls have a spiral winding very similar to rifling in a gun barrel. But enough of this and that. What your doing is making a spray bar for an aquarium filter discharge. Start with 1/8" holes and just try it. If the water sprays out with too much force or you feel it's bogging down your filter flow just re-drill to larger size holes. (I would not start 4x larger then the simple math first)
I've verified flow on my canisters simply by observation on water change day. With the tank a few inches short of filled (spray bar above the water line) crank up the filter and see how far and with what force the discharge sprays. If you feel like it's stronger flow then you want drill the holes bigger.

I purchased one of the Tom Aquarium Products Flow Meters when I was putting my sump system together but never used it.Sump pump keeps up with the drains and the tank stays clean so I don't care. (never opened the packaging so it was money wasted)

Landau, agreed there's more to it but what the heck, if the OP doesn't hit it spot on the first time we're talking about 42" of 3/4 PVC (cheap) and at worst case scenario a Saturday afternoon spent tuning the flow by re drilling the holes. I have here on my desk the McGraw Hill eighth edition Engineering Formulas by Kurt and Reiner Gieck. I'm not opening it for this post either so you can keep your text books I have enough heavy reading as it is. (but thanks for the offer)

IMO, (as all posts are) I'd drill that sucker and try it.

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post #18 of 19 (permalink) Old 04-05-2010, 07:37 PM Thread Starter
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Sound good to me. Thanks for the help. I'll give it a try and let you know how it goes.
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post #19 of 19 (permalink) Old 04-13-2010, 08:25 AM
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Wow. I built my spray bar several years ago and just guestimated like I described. It has been working great since I built it. My pump is still working good and I have even upgraded to a bigger pump without changing any of the holes. Maybe I just got extremely lucky the first time around and drilled the exact number of holes at the exact size needed and the exact length needed... all on a guess. Or Maybe it just isn't as precise as said and you can get away with pretty much whatever you put on there as long as there is not to much back pressure.

You can call my advice poor advice if you want, but I can say the same about yours. You are way over thinking this project. A pump will pump a certain amount of water based on the amount of back pressure applied to it. Back pressure can be caused by multiple factors including the height of the tank, the size of the hose, the number and size of the outlets and the amount of debris in the filter. If the number and size of the holes were so precise, then manufacturers would have to sell a different pump for tanks of different heights. You would also see alot more pumps burning out faster because of the tighter tolerances. Pumps are designed to handle a wide variety of scenarios. Don't believe me, look at the back of a pump next time you are at a store and you will see a chart on the back with the gps at different heights.

This is not rocket science. Grab some pvc pipe, start drilling till you find something you like. If you think my advice is poor advice, piss off and don't read it.
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