# A spraybar question



## Tomfish (24 Sep 2012)

I was under the impression that a full length spray bar gives you uniform flow along the full lenth of the aquarium. I have presently got a 1m long spray bar with 3mm holes placed 1.5 inches apart, centrally placed in a 4ft aquarium, powered by an fx5. What I am finding is that the velocity of flow is far higher at the furthest end than the nearest. I assumed that the velocity would equalise along the spray bar. This seems to bring into question the value of a full lenth spray bar from  one powerfull input. I have done a few searches and can't find any discussion on this. Any thoughts. cheers


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## ceg4048 (24 Sep 2012)

Hi Tom,
           If the output flow rate is low then there will be a pressure drop across the length of the bar. I think this unit has a 25mm hose. Is the spraybar a 1 inch tube or have you used a smaller diameter tube to fabricate the bar? If so then you will have killed your flow rate. The only way to improve the flow rate is to remove some of the filter media, especially the noodles if you are using those. Guys like Dave Spencer remove all of the ceramic media and use only chopped foam and a bit of activated carbon to improve filter throughput.

Cheers,


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## Tomfish (25 Sep 2012)

Hello Clive, cheers for responding. 
For the reasons you have stated I frabricated the bar from 25mm id tube. Am a right in assuming that the scenario you describe results in output reducing at the furthest end of the spray bar. If so this is not what I am experiencing. The flow from the furthest end of the spraybar is quite powerful (to such a degree that fish generally stay away from that end of the tank). It is at the start of the spraybar where the output connects to it that the flow is most reduced. I may well be wrong, but i would guess that if I increased the output, (by removing media) this would increase the flow from the spraybar, but not the disparity along its length.
l'm a bit unsure of why this is happening as it is a very powerful filter. I suppose my suspicion is that this is a normal property of spraybars that is not often appearent because of their normally shorter length.
cheers


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## dw1305 (25 Sep 2012)

Hi all,


> What I am finding is that the velocity of flow is far higher at the furthest end than the nearest


Don't quote me on this because I know zilch about engineering, but I think you need larger holes to equalise the pressure. 

My thinking is that the majority of the water is not escaping through the holes, but being dammed against the end of the tube. This back pressure will mean that the pump is capable of producing a lot more flow, if water escaped from the spray bar more quickly. Part of the problem is that the region of the bar nearest to the filter inlet will have non-linear flow as the water flowing in meets the dammed water from the end of the tube.

For the spray to be uniform along the bar you need the pressure to be equal at either end, with the amount of water arriving equalling the amount of water leaving without any increase in pressure along the bar. 

I think this makes sense and it would mean that if the velocity of flow is far higher at the furthest end than the nearest, you need:

Larger holes, more holes or a longer spray-bar (more area of hole for the water to escape from)
and if the the velocity of flow is far higher at the nearest end you need:
Smaller holes, less holes or a shorter spray bar (less area of hole).

cheers Darrel


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## foxfish (25 Sep 2012)

It is all about adjusting the spacing of the holes and the actual hole size, you may have to sacrifice this spray bar to use as a template!
Get some electrical insulation tape & your drill bit, either drill more holes where the flow is weak or tape up the holes where the flow is strong. It may take some experiment but you should be able to find the right balance - kept drilling & taping until you do then make a nice new spray bar with the correct spacing.
the chances of getting it right first time are pretty slim!!


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## Tomfish (26 Sep 2012)

Cheers Darrel and foxfish,
This is what I suspected. Nothing is ever as straight forward as one first assumes. It is surprising with the emphasised value of spray bars on this site that there is not more discussion on the nuanced nature achieving uniform flow.



			
				foxfish said:
			
		

> you may have to sacrifice this spray bar to use as a template!


I am hoping that won't be the case. what I'm thinking is to increase incrementally the size of the holes at the nearest end and combine this with lots of testing. Hopefully this way, I can find an equalibrium without doing away with my spraybar. Any thoughts? 
Cheers


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## Stitch (27 Sep 2012)

Firstly, I want to state that you're about to read advice from a guy that is only installing his first spray bar TOMORROW   

I have a thread in the DIY section and Clive (ceg4048) has been helping me too. He stated that the output size of all the holes needs to equal the output size of the hose, which makes sense.

I've tried to look online and it appears the FX5 outflow pipe has an Internal Diameter of 25mm. Is this correct?

How many holes do you have? I'm going to guess at 30.

Based on these values you're looking at the following (as a guide):

25mm diameter of the spray bar = 12.5 * 12.5 * 3.14 = 490.625 (square mm)
490.625 / 30 holes = 16.354
16.354 / 3.14 = 5.208 (radius squared)
square root of 5.208 = 2.282 (radius of small)
2.282 * 2 = 4.564

Therefore if you have 30 holes then you should be aiming for 4.5mm diameter holes. If I were you i'd try making the holes bigger.

This is as close as you're going to get without trial and error. Good luck.

I plan to keep my drill and tape handy for tomorrow morning.


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## MikeJojo (30 Dec 2013)

Stitch all that make sense and I just done my spray bar this way. My aquarium is 80cm long and spray bar is all the way on back wall. I read somewhere that diameter of all holes should be around 0.8 of hose diameter to be safe not getting bak pressure and maintain velocity. Having no many drills in my tool box I went for a drill to achieve just under 0.8 factor. Saying that I have spray bar producing equal streams along the length. The only problem I encountered was streams were not 90 degrees to spray bar as I drilled my holes holding drill in hand. I had one end of aquarium not really covered by streams because of that. What I did was to cut small pieces of co2 tubing maybe 5mm long and superglued right on holes not covering them of course but that gave streams a way to go straight out from all holes. It doesn't look pretty but it is my first spray bar. I will do next one using drill stand next time.

Hope that helps. 


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## Martin in Holland (20 Feb 2014)

I made a spray bar also just drilling by holding the drill in my hand, but I used painters tape on the tube to prevent the drill from slipping...all the streams are coming out straight from the holes 



even the fish seem to like it


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## MikeJojo (20 Feb 2014)

Hi Martin in China

Looks great but are you 100% positive all streams coming out straight? I wasn't aware until I had my spray bar tried in a bath. I undid shower head and used shower hose to provide water stream through spray bar. Try it and let us know  


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## Martin in Holland (20 Feb 2014)

MikeJojo said:


> Hi Martin in China
> 
> Looks great but are you 100% positive all streams coming out straight? I wasn't aware until I had my spray bar tried in a bath. I undid shower head and used shower hose to provide water stream through spray bar. Try it and let us know
> 
> ...


 
Yes I am positive....as I also tested it before using and with every WC I turn the filter on before the water reaches (about 5cm) the spray bar ...still looking good (if I remember it, I will take a picture next time)


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## MikeJojo (20 Feb 2014)

Good to hear you've managed to drill them by hand. I end up with kind of lily pipe. It worked better for me. It's kind of lily pipe because it's just bent acrylic tube with out lily pipe wide end. I never got that end right heating tube over the stove and do the blow to expand it.  

Regards 


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## sparkyweasel (21 Feb 2014)

It's not my branch of engineering, but I think Darrel's hypothesis sounds about right.


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## Martin in Holland (23 Feb 2014)

MikeJojo said:


> Hi Martin in China
> 
> Looks great but are you 100% positive all streams coming out straight? I wasn't aware until I had my spray bar tried in a bath. I undid shower head and used shower hose to provide water stream through spray bar. Try it and let us know
> 
> ...


 
Looks pretty straight to me


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## foxfish (23 Feb 2014)

Looks straight alright but not very powerful or perhaps too many holes?
I have found you need the spray to reach the far side to work efficiently.


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## Martin in Holland (23 Feb 2014)

It's not to many holes but I drilled the holes a bit to big I think also it's now only showing about an inch above the water


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