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Old 05-05-2006, 04:33 PM   #11
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I don't see how you are going to prevent a siphon break on the water out tube, therefore I predict a tank flood if RO input is greater than tank evaporation? Or perhaps I do not unterstand your system? Unless it is designed like an overflow box or with an overflow box in it ,how does it work?

Otherwise, you could just send the RO output to a holding tank. Then use pumps to get water out of the aquarium, and back into the aquarium with the flip of a switch. Sure, its not a gradual, continual thing, and it will require you to flip the switches, but it works.



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Old 05-05-2006, 04:58 PM   #12
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I think the setup is like this: in which case there is no syphon - just a long overflow to his sink

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Old 05-08-2006, 05:23 PM   #13
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Quote:
Originally Posted by hashbaz
It is normal for the water to rise as it builds enough height difference to drive the siphon.
Alright I had figured that the differential would be negligible but perhaps it is not. I will lower the output height and use post-its to track the rise and fall; perhaps it is working as intended.

In regards to the next post, there is no siphon break because the amount of water below the tank level is greater than the small amount of water above the tank level at the beginning of the siphon. For a break to occur all the water below the tank level (and also below the output level) would have to flow out, and that will never happen, because that would mean that the waterline in the tank is below the waterline at the output. After the tube leaves the tank it never rises above the waterline until the exit point.

In regards to tbone's post, there is a siphon. It is not merely an overflow.

Code:
drain     tank            
.__        --
|  |      |  |
   |      |   
   |______|


. = airhole
The waterline is equal to the height of the airhole.

That explanation is not very good. But I can say: it does not happen in my tank. And I refuse to use pumps, only physics. 8)

~perle
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Old 05-08-2006, 07:02 PM   #14
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What I can't understand, is that if there is a siphon hole to stop the outflow of water once the water level drops, then the siphon will be "broken." Then, when the water level rises again, the outflow will not start back up unless someone goes and sucks on the end of the tubing. There lies the risk of tank flood. If it is not noticed that the outflow has ceases, yet the RO water continues to go in, you can overfill your tank.

Take a look at how a HOB overflow box is constructed. There is not one continuous enclosed path the water takes, this is in order to prevent the sipohon from being broken by a drop in water level and/or a reduction or stopage of water flow. With HOB overflow boxes, there is always the risk of air entry into the inverted "J" tube that goes over the tank rim with loss of siphon, but this is rare. I believe it is rare because the water flow through the J tube is brisk, tending to flush bubbles out. Built in corner overflows have no risk of siphon loss, and can only cease outflow if clogged.

So I guess I just don't understand how your set-up works. But, I like your idea of slow continuous water exchange, and commend you on your dedication to improve your fish's environment.
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Old 05-08-2006, 07:22 PM   #15
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Quote:
Originally Posted by TomK2
What I can't understand, is that if there is a siphon hole to stop the outflow of water once the water level drops, then the siphon will be "broken."
This is not true. The left loop of the "m" shape of the siphon is the key. It is the same principle that lets you temporarily pause the use of a gravel vac by raising the exit end just above the waterline of the tank, and then resume it when you lower it to your bucket again.

hashbaz, would I get more output pressure if the intake of the exit tube was lower in the tank? Since there would be more water pushing down above it?

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Old 05-09-2006, 01:04 AM   #16
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No, lowering the inlet to the outtake tube will not increase the flow . But it might make it less likely for bubbles to into your system, and ruin the siphon .

If it helps, Perle's tube works just the same as an overflow box. - it keeps water in the "" over the side of the tank. Water will stay in the "U" outside the tank, keeping air from getting into the "."
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Old 05-09-2006, 01:07 AM   #17
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Hmmm. I see tbones diagram, and I understand it and see how it would work. With no airholes, water only comes out of the sink end when the tank level rises above the sink end, and the tank level is determined by the height of the sink end. But what is the purpose of the airhole? I would assume it is to allow air in to break siphon when the water drops below the desired level in the tank, thus preventing too much water from going out. Everything works fine as long as the water stays above the airhole, and air doesn't enter the tubing. But like you say, if the tube empties of water, like would happen when the water level drops below the airhole and air is let in, then no more siphon?

Ah well, I guess I just won't get it. But I would test my theory, and drop the tank water level below the airhole and see what happens. And please forgive my lack of understanding !

edit: uh, so you saying that since only a small amount of air gets into the tubing on the tank and sink side when water drops below the airhole, compared to the larger volume of water in the loop below the water line, the siphon will restart with just a rise in water level and no other intervention? Well toast my buns.
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Old 05-09-2006, 12:30 PM   #18
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I guess the issue with the syphon breaking all depends on how low the input tube for the exiting water is in the tank.
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Old 05-09-2006, 12:34 PM   #19
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Quote:
Originally Posted by tbonem91
I guess the issue with the syphon breaking all depends on how low the input tube for the exiting water is in the tank.
No, that is unrelated. As long as the tip of the input tube is underwater the siphon will not break.

In other news I am running the system 24/7 now with no problems. Still waiting for my R/O Right salts (should be any minute now!). According to my quick and dirty measurement attempt I am cycling ~6 gallons a day.

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Old 05-09-2006, 01:16 PM   #20
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Quote:
Originally Posted by perle
Quote:
Originally Posted by tbonem91
I guess the issue with the syphon breaking all depends on how low the input tube for the exiting water is in the tank.
No, that is unrelated. As long as the tip of the input tube is underwater the siphon will not break.
yeah - thats what I mean - all this hypothetical talk of overflowing deals with IF your input stops, the water level drops below the input, then it starts back up again. I guess that could really only happen in a situation where you were gone for a while, the power went out, water evaporated like crazy to the point where it fell below the inlet, then the power came back on and your RODI overflowed.

I think that is the only real hypothetical situation where this would fail - and could be remedied (unless you already have this) by an inside overflow box that always keeps the inlet submerged regardless of the tank water level... then the tank level would flow into the interior box, etc.

This is actually a really good idea as a water turnover system - so long as your tank has a place for the water to go on the same level as it and the outlet tube has no way of ever being displaced as that would either drain the tank to the level of the inlet (outlet fell/dropped/etc), eventually causing an overflow of the tank via broken syphon or directly cause an overflow of the tank (outlet was somehow raised)

when and if I ever move into my own place and set up my planned big tanks, I might utilize this method depending where I put them... it could also work in a sump setup - the drain hose would just have to be much lower... and would work really well in a basement
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