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Old 11/03/2016, 11:24 PM   #1
My reef tanks my wallet
Join Date: Dec 2011
Location: Portland
Posts: 498
Can SW reservoir line go below sump?

If the SW reservoir is 6' higher than the sump but the line drops 4' below the sump, will this cause problems? My line goes under the house. Once I fill the line with SW will dropping the first gallon result in slightly more than a gallon exiting due to a small siphon effect? And then the next gallon dropped will be slightly less (the difference from the first) and then alternate like that?

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Old 11/05/2016, 08:00 PM   #2
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Location: Simi Valley, Ca
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The metering bins can only hold 1 gallon. As such, the first dump may result in slightly less than a gallon going back into your sump assuming some remains in the line. The again, the siphon effect may just remove all the water from the line. Even if some does remain in the line the first run, after that, it should be fine because the line will only retain so much water and the end result is that a gallon will be passed into the sump. I think your setup will work just fine.

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Old 11/06/2016, 05:14 AM   #3
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Good morning Zalick,

Thanks for asking a great question!

While this might work with special considerations and setup, it isn't something I generally recommend - especially if the water can sit in the tubing for a long time. But the major reason I don't recommend this is because the water that remains in the tube can create an air lock in the tubing.

Our Metering Reservoirs - the bins that hang on the wall and make sure that exactly one gallon is removed and exactly one gallon is reintroduced into your aquarium system - drain via gravity. They have a little less than a foot of water column in them when they are full. The weight of that column of water is all that can push the water out of the tubing, and it first has to compress the air that is in the tubing, which then pushes the water. If the weight of the column of water that remains in the tubing exceeds the weight of the water pushing down from the Metering Reservoir, the Metering Reservoir can't drain its contents into the tubing. The water just sits there or just barely trickles out.

In many cases you can try a workaround to allow the air trapped in the tubing to vent. What we want is atmospheric pressure in the tubing - we want it to vent to the atmosphere so the water from the Metering Reservoir can push the air out and flow into the tubing. Then, as the water column in the tubing increases, it pushes the water that was already there out in an equal amount... One gallon in, one gallon out.

To vent the tubing and prevent it from pressurizing, I would add a tee to the dispense tube a couple inches below the valve on the Metering Reservoir. Then add a piece of tubing to the branch of the tee, and route it such that the end is higher than the top of the Metering Reservoir, and affix it to the wall. This allows air to escape from the tubing as water flows into it, and it prevents the possibility of water ever coming out of it. This tubing should be kept as short as possible, maybe 18" or so, and it's very important to make sure that water cannot collect in this short segment of tubing.

sleif is right: the first couple gallons (however many gallons it takes to fill the portion of the tubing below the end in your sump) will be removed from your sump but won't make it back in. You'll need to manually add that same volume to your sump when first starting the system and "priming" the tubing. Then it should begin to function as intended.

There may be a little (or a lot!) of trial and error to get this type of setup just right, but as slief indicated, once you get it dialed in it can work. Because of the added complexity and setup woes, I generally will strongly discourage this type of setup for most systems. However, as long as a person realizes it is not typical and is going to behave a little differently from most RENEW™ systems - I say "go for it!"

Please let us know if you have any questions, and please post pics of your installation!

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Last edited by GenesisReefSys; 11/06/2016 at 05:18 AM. Reason: I hate typos!
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Old 11/06/2016, 06:46 AM   #4
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Join Date: Dec 2011
Location: Portland
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Thanks Kevin and Scott!

I had not thought of the back pressure. This is my only option though, so glad it can work!

Kevin - thank you for the email too. The line will only have water sitting in it for 24hrs and my total system volume is about 380g, so I don't think bacterial buildup or anaerobic water will be an issue. I currently use the pipes but I have a valve that dumps the stagnant water down the drain first.

I plan do to do 3gpd through the system, so only 1gallon would-be stagnant. Do you think this would be fine?

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