View Full Version : Closed Loop Flow Control Necessary?
BiscayneA1A
01/06/2008, 09:24 AM
I'm designing a closed loop for my new 100g. I'm ordering a Sequence Reeflo Snapper (1,900 gph @ 4')
Before I began to cement the pvc parts together I had to pause a minute thinking that the flow nearest the feed line would be greater than those outlets furthest from the feed line.
Should I/do I need to add some sort of ball valve to control the output? I think I've read somewhere that in a closed loop set up the output equalizes at each outlet. Can anyone confirm?
Thanks.
dsanfilippo
01/06/2008, 10:30 AM
No it won't equalize from discharge to discharge... the water will aleays take path of least resistance... it is the pressure loss due to elevation that equalizes out.
BiscayneA1A
01/06/2008, 10:42 AM
Thanks. That's what I thought. I may have to re-think this a bit. In all the closed loop photos I've seen posted, none that I remember had any flow controls on them. I wonder if I put 1/2" fittings nearest the feed line and 3/4" or 1" fittings at the farthest point that would help to balance it out. Any thoughts on that?
BiscayneA1A
01/08/2008, 08:09 AM
There were a lot of posts related to closed loops a while back...I know you're out there...Anyone care to comment on the disparity of the flow and how you compensated. I'd hate to add a ball valve on each of the eight outlets. Any and all suggestions appreciated.
bluewatercandy
01/08/2008, 08:20 AM
On my closed loop with about the same flow as BiscayneA1A, I made a complete loop around the top of my tank with 1" pvc. The supply from the pump T's into this loop and all the nozzles T off from this loop... This allows the pressure to remain the same at each outlet.
dzeadow
01/08/2008, 08:30 AM
don't most CL's have ball valves near their outlets to be able to control the flow to each one?
BiscayneA1A
01/08/2008, 08:39 AM
Ok, so I'm confused. Bluewatercandy and dsanfilippo seem to be contradicting one another.
assiegordon
01/08/2008, 11:30 AM
To put it simple.
The only way to get away with not using any valves and still maintain the same flow at each outlet is to ensure that the pressure loss for each "path" is identical (no path of least resistance). Since this is a closed loop, there is no pressure loss due to head, it's all friction (through elbows and pipe).
Making a loop does not ensure the same flow at each location, you'd still need a valve.
Now, you don't need a valve on every outlet, just on the nearest. As you throttle the flow down, the flow at the other outlets will increase.
Have fun!
Jim.
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