Re: Number of Holes for Spray Bar

["S. Hieber" <shieber at yahoo_com>]

Greger Lindstrand made a few comments about this topic,
saying in part:

> I have to ask because I don't really understand the
> hydrological debate on number of holes etc. in a
> spraybar.
> 
> I have manyfactured my own spraybar 140 cm long and
> drilled 4 mm holes about 10 mm apart over the entire
> length.
> The spray is evenly distributed along the entire length.
> Now, did I get the number of holes correct by chance? Or
> is there another explanation to this?
Getting the flow level and pressure to be about equal, for
practical purposes, is not so hard if you don't care about
the amount of flow.  The fewer the holes the higher the
pressure, up to the maximum head pressure the pump can
build.  On most pumps two holes will pretty much the same
flow.  The trick is getting an even flow *and* minimizing
restriction of the flow.

> 
> Well, I thought about it and came up with something that
> may differ from most setups and maybe this is the trick.
> You tell me, I'm just guessing.
> 
> The bar; The spraybar is built in a L - shape. The short
> part (60 cm) stands in the corner and is open to air on
> top. Right beneath the cover glass. The other part (140
> cm) is burried in the gravel over the length of the tank.
> Water from the pump (Fluval 404) enters at the top. There
> is also a tube comming from the reaktor-S (CO2 reaktor
> driven by it's own Ehiem 2252 pumphead) and it enters the
> same opening.
> Should all holes be covered at the bottom of the tank,
> the water would surely overflow the open opening where
> the pumps deliver their water. 
> Otherwise it don't overflow at all, inspite there beeing
> only 1 cm from the tube top to the waterlevel.
> 
> Question: Could it be that the open to air top, equals
> out all hydrological pressures, thus giving an even flow?
> Or have I just been lucky and got the number of holes
> right?
> 
> The pipe is an ordinary plastic plumming pipe, used under
> the bathtub and so on. Diameter is 30 mm.

In a large tube open to the atmosphere, you are relying on
gravity to create your water pressure, not the pump.  With
a very tall column of water and many holes, then the holes
at the bottom (the end) of the bar would have the strongest
flow.  If you had a really tall column of water and only a
few holes, the flow coming out of each would be about the
same.  
> 
> The trick: The open to air top. I assume that most ppl
> connects their Ehiems & Fluvals directly to the spraybar,
> wherefore the pressure inside the spraybar is direcly
> linked to the output of the filter pumphead's capacity.
> Please tell me if my assumption is wrong.
> 
> How did I come upon such a brilliant idea? I didn't. I
> was just beeing lazy and in a hurry to get the tank
> going. Hooked things up and thought I'd fix that later.
> But it works perfectly! And following the device; If it
> works, don't fix it! I continue to let it be :-)

You'll never invent a better light bulb if you never try to
improve what works ;-)

Scott H.

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