# A hydraulics question. Spray bar how many holes?



## Freemann (Mar 19, 2004)

I am trying to run a spraybar all along the back of my tank near the bottom. This will be run from a power head which is 1500lt/h, Hmax 2.15m. I have been using this pump for some time but it moves the plants sideways and I don't like it the nozzle of the pump is 16 mm and the water goes all the way in the front side to the other side of the 149 cm tank and turns back again on the back of it when hitting the glass.
Now this is the question how many holes should I open to the 109 cm 16 mm pipe I have so the water will have just enough pressure to travel the 50 cm to the front side of the tank and what size should the holes be? Suggestions?


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## LilLou (Apr 23, 2006)

I would try to open 16 3mm holes in the pipe to start and then either:

Increase the size of the holes 
Increase the number of 3 mm holes

Both will decrease the pressure because you are increasing the area through which it is pumped. 
The actual flow may increase due to less resistance on the outlet.
Make the adjustments above till you get the flow you want. I hope I am close in my estimate.


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## furballi (Feb 2, 2007)

It depends on the depth of the spray bar (head pressure of water column). Start out with the desired number of holes and gradually increase the hole's diameter toward the end of the spray bar. I'd start out at 2mm and work up to 4mm at the other end.


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## Hashbaz (Apr 23, 2006)

Can you aim your spraybar differently? I used to have my spray bar mounted vertically and aimed so that the water came out parallel to the back glass. This resulted in the entire aquarium becoming 1 big water current. I then aimed the holes in the spray bar so that they hit almost straight against the back glass. This eliminated the high currents pushing my plants sideways.

Driling more/larger holes will decrease the velocity of the water coming out. Putting the holes in different dirrections will reduce the overall currents made by the spraybar.


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## Freemann (Mar 19, 2004)

Hi and thank you all 
So we have a number of alternatives:


> 16 holes


I was thinking in the terms of 30 but that was just a guess. Is your suggestion based on some calculations?


> It depends on the depth of the spray bar (head pressure of water column). Start out with the desired number of holes and gradually increase the hole's diameter toward the end of the spray bar. I'd start out at 2mm and work up to 4mm at the other end.


Well that sounds a credible suggestion as well, increasing holes size while pressure drops towards the end of the pipe, something else I have read as well concerning water flow through the holes when going towards the end of the pipe is setting barriers on the opposite side of the direction of the flow in each spray hole, which will be longer the further away from the water input they are so water hits on them and is directed upwards towards the hole. By the way depth is 35 cm


> Can you aim your spraybar differently?


This is a good suggestion as well maybe directing alternative holes in a different angle in relation to a horizontal line drawn on the pipe maybe a few degrees upwards and downwards alternatively.

So what is the summary of it all?
Do I still drill 16 holes and do all the rest as well?
I wonder


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## LilLou (Apr 23, 2006)

Freeman 

My estimate was based on area of tube and holes.

I like the idea of increasing the hole diameter towards the end and getting smaller near the pump source. That just makes for more calculations. 

a 3mm hole has an area of 2.35 sq mm

a 16 mm tube has an area of 12.56 sq mm

16X2.35 = 37.60 sq mm

By increasing the area by 300% should decrease the flow by the same.

500l/h / 16= 31.25L/hr per hole roughly.

That's where my numbers came from.


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## gibmaker (Jan 3, 2007)

Well I would not bust out the calculator for this one, I would just evenly place the holes and if the spray bar pops off from to much back pressure.........add more holes. It seems to me that people tend to over think certain processes. Start out with a smaller number of holes evenly placed and then add more if needed.


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