Will increasing spray bar adjust filter flow?

BoneyT

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Hi All

Firstly apologies if I have posted this in the wrong section I am new to the forums...

I have a 5 foot tank, my filters spray bar is 80 cm's if I created an extension to cover the length of the tank would this have a) an impact on the flow rate of the filter? b) a positive effect on the tank?

The logic behidn this question is as follows

I have a eheim skim 350 at each end of the tank so the tank isnt struggling for water flow, but I plan to move my co2 outout to inline so the extended spray bar will hopefully circulate the co2 more evenly at its initial output

Thanks for reading!
 
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Simon Cole

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Spray bars are affected by Bernoulli's principle. This means that you may reduce pressure on the motor if you increase spray bar length, but more water will always come out from the end nearest the filter due to the pressure differential. Theoretically it is possible that this could increase overall flow, but it will never be even across your tank. I think the premise of using spray bars is to minimize surface flow so that less carbon dioxide in tank water is lost to the air. If you already have good surface flow rates around you tank then I cannot see this having a positive advantage over a standard outlet. Pushing carbon dioxide rich water downwards towards plants and away from the surface is a very good idea, but then it would make more sense to have the spray bar positioned at plant height.
 

BoneyT

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Hi Simon, thanks for taking the time to respond, seems like the results would be minimal if any, Unfortunately I don't have the parts to reduce the spray bar to plant level but they are all at different heights anyway, I will position the bar to hit the plants at a 45 degree angle and see where it goes from there.
 

Simon Cole

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Sounds spot on. My Dad has been working with me on the physics of filters and a while back he pointed this out. If the flow is backing up in the spray bar then an extension would help but this does feel minimal. The thing is that carbon dioxide flow is so important that you might find even a small change could reduce algae and improve plant health, so don't rule it out. It seems like you have the best arrangement possible anyway with the water kinda going from the outside in and down.
 

foxfish

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Well there is more to it than that but the main advantage of a spray bar is that is causes a circular flow within the tank.
So the flow is projected across the the top layer towards the front pane, then down the front glass across the bottom and back up toward the spray bar.
In theory this flow should pass the C02 enriched water right through the plant mass over and over again.
On that basis a full length spray bar would be the most efficient .
There are some formulas that calculates the number and size of the holes but I am dubious if they actually work. I much prefer to use sacrificial cheap tube and experiment with an drill and electricians tape to find the best configuration!
However a full length spray bar with 2mm holes every 50mm is always a good start from my experience.
 

ian_m

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You can experiment making spray bars with different hole sizes and locations by buying a length of say 16/18mm (thinwall) PVC tubing. 3 meters cost me £1 at local water feature/pond shop.

Tape it to a piece of wood, to keep it straight and stop it rotating whilst fiddling, mark up with a permanent marker say every 30mm, and drill say 1.5mm holes. If you accidentally drill out the back, tape the hole over. Use this as test spray bar.

Easy to modify, by increasing hole size, blocking off holes with tape etc. If not really happy just start again with another piece of pipe say 50mm spacing and 2mm holes. Some people have messed around with 21mm PVC overflow pipe as only £1.50 odd for 3 meters, issue with this is connecting non standard 21mm to standard 16/22mm piping.

Some people quote a "theory" that the total area of all your holes (using pi * R2) eg 2mm hole = 3.1mm2 should be same as cross sectional area of your pipe eg 16mm pipe is pi x 8 x 8 = 200mm2, so as to not affect "flow".

In the end I proved the the Juwel internal pumps can't really power a spray bar and the the JBL supplied spray bar bits were perfectly adequate even when I extended the supplied spray bar.
 

BoneyT

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Thanks for the response @ian_m and @foxfish (ps this spray bar issue is the precursor to me setting up your co2 reactor so expect to hear more from me soon!!)

So I can test this, by seeing the water output from the current solution, and then adding a longer custom piece to the tank, to not have a loss in flow the water wants to be hitting the tank wall at the same height?
 

Andrew Butler

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Some people quote a "theory" that the total area of all your holes (using pi * R2) eg 2mm hole = 3.1mm2 should be same as cross sectional area of your pipe eg 16mm pipe is pi x 8 x 8 = 200mm2, so as to not affect "flow".
All just my opinion but I completely disagree with this theory from experience.
I've made a few spraybars now and after using this theory a few times looked to the spraybar that came with my filter and wondered why there were so few holes and decided to experiment more with the amount and size of holes that came with my filter. I was using Fluval G6 filters which also come with a flow display so I would know if the holes were too small also. (I wanted to make a spraybar that filled the width of my aquarium a bit better which was the reason for making them)

I found feeding the spraybar from a tee made flow more even whereas feeding it all from one end meant the end could lose flow or the jets shot in the flow the spraybar was being fed from moreso.

I have a eheim skim 350 at each end of the tank so the tank isnt struggling for water flow
Do you mean the small separate skimmers? - I'm unsure I'd rely on these for creating flow as it could end up fighting your spraybar.
 

BoneyT

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Hi Andrew, unfortunately a T junction isn't possible, the installation room isn't there to fit it. I have brought a length of PVC tubing at lunch, if it doesnt work its only £3 wasted

Do you mean the small separate skimmers?
Yes.

As of the moment the output from the eheim's come underneath the spray bar so there isn't any interference, I use two to push the co2 about the tank more, the end plan is to get rid of the diffuser and use an inline solution for co2 output so I can reduce the skimmers down to one if the extended spray bar helps with distribution
 
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