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spay bars and pond filters

M

morefirejules08

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Joined
15 Sep 2011
Messages
151
hi
i have mentioned in other threads that my 560l tank runs a pond filter and pump, the pump is rated at 4000lph and it all flows though 30mm ID pipe work. i have now been reading that a spray bar would give me goo circulation but what i would like to know is how to go about making a spray bar for 30mm pipe work! should i step the pipe down to a smaller diameter or just use 30mm solid pipe with equal holes drill along the length? how big should the holes be? the only draw back is the OD of the pipe is 36mm so its going to look pretty rubbish!
if i step down in size will i create a back pressure and reduce flow!!

sorry about all the questions :D
 
Hi,
What's the big deal? Just use clear acrylic tubing with near 30mm ID. Figure out what the cross sectional area of the pipe is and that will be arough guide as to what the sum of the cross sectional areas ought to be for the holes. Figure out how many equally spaced holes you'll have and divide that number into the total area. That tells you how much area each hole should have and then solve that equation for the hole diameter.

Cheers,
 
thanks for the reply, to get the cross sectionl area i need to calculate, pi x half the inside diameter squared?
if so then i get 3.14x15^ which gives me 706.5mm so i guess i then just divide that number b the amount of holes and equally space those holes across the lengh of pipe.
with that in mind would i need to take into account flow losses across the pipe?
with regards to CO2, could i diffuse it straight into the spray bar at the point before the first hole?

cheers
 
The first part of the calculation seems fine.

I think you now need to decide on the diameter of the drill bit you want to use, work out the cross sectional area (csa) of that using the same formula (pi x r^2), divide the csa of the pipe by that of the holes to the nearest integer.

Then take the length of the spraybar (might be worth taking a couple of cm off to account for the join) and divide it by the number of holes to give you the space in between.

Hopefully Clive will check this because i've probably oversimplified, I'm not sure whether it's a good idea to add a few extra holes to account for the extra pressure caused by forcing the water out of such a small exit.

That said i'd probably do the minimum amount using the above method, check to see if the flow agrees with your aquarium and add more if it's too strong. It will be easier to add than take away in this situation.

Joe
 
Well there are some frictional losses along the bar and some pressure losses across the holes, as well as the fact that the water has to turn 90 degrees to exit though the small holes, but we're not designing a rocket engine, just a simple spraybar, so these calculatios will suffice. Pi*R squared divided by the number of holes works fine. Then solve for R of the small holes and match that to a standard drill bit size. As mentioned, keep the axis of the holes perpendicular to the length of of the bar because the energy loss of the water turning is more significant than the skin friction loss along the bar. If you can smoothen the edges of the holes that helps a lot as well.

Cheers,
 
ok that shouldn't be a problem, what would be the best way to introduce CO2 into the water flow to ensure its gets distributed well?

cheers
 
I think you could reduce the pipe t0 25 ID with a straight reducer without too much flow reduction.
You can place the spray bar right at the surface level so it is not so noticeable as you might expect!
The problem might be getting the pipe over the top of the tank without using two pipe elbows as thatwill reduce flow.
As I dont know the tanks siting or how much room you have it is difficult to suggest the right approach but it might be possible to use some flexible 32mm suction pipe to carry the return over the tank lip?
As regards the Co2 - you might be able to T off your vertical return with some barbs & a loop of 16mm flexi pipe to catch one or two in line atomisers..or enlarge the pipe work for a sort section to 50mm & install a diffuser.
I could draw a diagram...
Or perhaps go down a completely different route & install a needlewheel powerhead connected directly to a spray bar = very easy - very efficient but, a little unsightly!
 
I'll have a look at the power head solution. The tank has been running for a few years with the pond pump/filter and it would just be a case of attaching the spray bar to the existing outflow pipe as it is just made up from a 90 degree flexi hose fitting at the moment. i may also messure the ID of the current outlet and find a pipe to fit inside rather outsite which should take away the need for a reducer and lower the cost of the pipe. All i would need to do then is figure out distributing the CO2
 
I use this one in my tank http://www.charterhouse-aquatics.co.uk/ ... -2701.html although it is fitted in my sump.
The ease of use, no maintenance, not ever any pressure required from the C02 source makes for a very easy & efficient gas distribution method - however they do produce a fine mist.
 
i think i may change my current flexi hosing and fit solid 25mm solid pipework with a home made inline reactor similar to the http://www.rexgrigg.com/diy-reactor.htm reactor.
i would need to instal it horizontally as my filter and pump are in a room behind the tank so i have no vertical outlet pipe work!
 
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