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-   -   Air /water mix standpipe drain system (http://www.reefcentral.com/forums/showthread.php?t=1828891)

mbrady 04/07/2010 10:53 AM

Air /water mix standpipe drain system
 
I currently have a AGA megaflow standpipe in my reef ready aquarium.
I assume this is a air / water mix standpipe drain system. I read some where that it is really a Durso standpipe design (give credit were credit is due).

Can this drain system be split into two feeds into my sump with some type of control value conected to it?

jacksonpt 04/07/2010 11:06 AM

Probably could, just depends on how much room you have in the stand. Why would you want to?

uncleof6 04/07/2010 11:19 AM

It is nothing but a high priced "durso" modified standpipe. You can make your own for a bunch less, and yes it is an air/water mix standpipe system-- subject to the same flow restrictions (for trouble free operation) as one that is made from easily obtained pvc fittings.

Air/water mix systems are very touchy with restrictions in the lines, and geometry of the drain line. Angles, turns, 90's, valves etc., all cause turbulence in the lines, causing the air and water to mix, rather than remain separated. It is less problematic to feed other equipment or areas in the sump from the return line, rather than the drain line, and keep the drain line as straight and unrestricted as possible. I.E. no valves, no 90's, splits what have you. Valves are used in siphon drain lines, to set the water level in the over flow.

Jim

mbrady 04/07/2010 03:19 PM

Uncleof6---Follow up question
 
Drain pipe flow Rate

What is the megaflow standpipe flow rate?

I am currently running an external pump (Iwaki Model #30RXT) which is rated at 900 gallons per hour with an 8 foot head. It runs straight out with no flow control value.

I beleive my return pump is to strong. What do you think.

90 gallon Tank.

uncleof6 04/07/2010 05:08 PM

The flow rate it will handle without problems depends on numerous variables, however 1.5" standpipes (air/water mix) show symptoms as low as ~ 320 gph-- it can vary. Problems always include noise, bubbles in the sump, and often "toilet flushing." You have not stated any problem, but I would think there is some kind of problem: there should be if you have 900 gph going through an air/water mix drain. You said you believe your pump is too strong, I disagree that it is "too strong" for the system you have. I believe it is "too much" for an air/water mix standpipe. If there is a problem, splitting the drain line will not solve it, but splitting the return line (robbing some flow) will help with the problem-- if there is one. If it is merely should I split the drain line to feed "fuge", it is better not to split an air/water mix drain for reasons above. If it ain't broke-- that just might break it.

Jim

billdogg 04/07/2010 05:25 PM

1 Attachment(s)
Please refer to the attached chart to determine your approximate drain capacity.

As you can clearly see, a 1.5" drain can pretty easily handle AT LEAST 700gph BEFORE siphon effect.

1' drains, on the other hand, which I think is what the megaflow is, begin to have issue at ~300 to 350gph

uncleof6 04/07/2010 06:13 PM

billdog, the chart that you posted concerns blank bulkheads, and does not consider interaction with the standpipe. Max flow capacities for bulkheads, or even pipe sizes is relevant to the discussion, but not in the way you are presenting it. The issue is laminar vs turbulent flow. Laminar flow, that will be silent, bubble free, will be far below any max capacity of a given size bulkhead, OR given size stand pipe. The bubbles and noise annoy most people, and the number of threads on the subject far to numerous to ignore. There is a commonality, that can be seen even if the physics are not understood-- or even known. It is always because the flow rate is too high, and/or restrictions in the drain line. A 1" air/water mix standpipe will have problems way below 300 gph, and the inventor of the "durso" states clearly that a 1" durso, is of no real use-- except with extremely low flow rates. My comments have nothing to do with max flow through a bulkhead, through a particular size pipe, or with siphon systems. An air/water mix standpipe flow goes up, thinks about siphon, the "toilet flushes" = flow rate too high. Flow in the standpipe is not laminar (noise, bubbles with or with out "toilet flushing" = flow rate is too high. Laminar flow in a standpipe, is very low relatively speaking. The physics win.

I think before this gets too far, and the OP goes away, give the OP a chance to address the question of what the exact issue is, if there even is one. He stated "i believe my return pump is to strong," that is only telling to a point. :)

Jim

das75 04/07/2010 06:56 PM

I've split from one on my drains to feed a fuge and controls easy with a ball valve. Can't see splitting though giving more overall flow than a single line would.

http://i67.photobucket.com/albums/h3.../sump_fuge.jpg

mbrady 04/08/2010 09:01 AM

OP Response
 
My megaflow standpipe drains into a Megaflow wet dry now. The water falls through another PVC standpipe into a section in the wet / dry that is 13 1/2"L X 3"W X 17'' high. This section is enclosed except for two inchs from the top one one side. The water than flows over a baffle into a prefilter tray into the sump section. Yes there are air bubbles, occasionally a little toilet flush affect.The bubbles dispate after a short while and do not make it to the return pump. As far as noise the hum from the pumps is louder than the overflow.
If the suggestion was do not split the drain but split the return. I was concerned with limiting the flow back into the main tank. If as suggested the max flow on the drain side is 300 to 600 GPH than a return pump rated at 900 GPH seems to strong. What happens to the 300 GPH difference or does the pump only operate at what the drain pipe flow rate.

MY ultimate goal is to replace the Megaflow wet / dry with a DIY combination sump and refugium.

My concern is presently I can live with the current set up bubbles, occasional toilet flush and little noise.
If I change out the wet / dry with a DIY Sump will I create something I can not live with

mbrady 04/08/2010 12:20 PM

Uncleof6---response to flow rate
 
See my Original post response


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