Question: Return Line w/ Vivid Creative Aquatics Random Flow Generator

Emerson

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I have a split return line with two 3/4" loc line lengths slightly below the surface on my 90 gal tank. I swapped out 3" flare tips on loc line extensions with the VCA Random Flow Generator nozzles. These things are a little pricey, but work great at what they're supposed to do: create random flow, and lots of it (see the link at the end of post).

My issue is this: if the nozzle is too close to the surface, it frequently draws a little air vortex/tiny whirlpool at the collar near its base, almost like a bypass on jet engine, and creates micro bubbles and a slurping noise. To prevent this, I have to keep the nozzle further below the surface than I'd like, creating a back siphon hazard that could overflow my 20 gal sump. I have Fischer wye check valves on both return lines which used to be the redundancy against back siphoning. In this configuration they end up primary, and a failure waiting to happen.

Is anyone else using the VCA RFGs having similar issues? Any recommendations? I don't want to push the nozzle any deeper. It's not practical to fit a bigger sump to accommodate the nozzle. I've thought about using some epoxy putty to plug the top of the nozzle bypass to disturb the Otherwise I think I'm just back to the flared nozzle. Sorry, I know pictures would be good, but can't post any right now.

Thanks for any input.
@ Vivid Creative Aquatics, your insight especially valuable!

(https://vividcreativeaquatics.com/product-spotlight/random-flow-generator/)
 

ca1ore

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This is the major flaw to these kinds of things (penduters, educators, etc.). They have to be submerged low enough that they don't suck air. You could try blocking the openings that are closest to the surface to see if that helps. Otherwise, you need to plan for more drain down. FWIW, I use mine on a closed loop return where being submerged lower is not a problem.
 

Bayareareefer18

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I actually posed this exact question to them yesterday. Even my flare nozzle can cause this issue. I was curious how close the RFGs could be to the surface without having that issue....
 

Kyl

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Is any portion of the loc-line higher than the bottom of your overflow weir? If so, drill a small hole in the underside of the loc-line above that level, and the siphon will break as soon as it's exposed to air from draining.
 

drtrash

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I think the nozzle will continue to draw water even with hole in pipe but i could be wrong, will lower my locline flare before going the rf route
 

Kyl

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If the hole is exposed to air and the height of it is above the lowest point of the weir, it cannot draw water.

What size hole do you recommend?

I believe the hole I made was 1/8". If you screw up, it's just a single piece of loc-line to replace and not a whole pipe :)
 

drtrash

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Most weirs are only 1" below surface so maybe chasing a sweet spot of 1 1/2" below surface for nozzle
 

Fishfinder

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it can be above or below the weir. The higher you drill will have less drain down. I had to drill a hole in my loc line also. I drilled it in my first link because that is my highest one.
 

Bayareareefer18

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I think the hole I drilled was maybe 7/64. I had been running my nozzle really close to the surface. After drilling the hole just below water surface and lowering the nozzle that really cut down on the noise at the weir
 

Vivid Creative Aquatics

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Sorry for the slow response here and thanks for everyone chiming in - all great suggestions.

@Emerson, at the higher flow rates the RFG nozzle definitely need to be lower below water's surface. Depending on the flow rate, you will need to have the nozzles anywhere from .25" to as much a few 1.5" below the water surface - as measure at the educator end.

There are a few tricks can sometime help minimize them sucking in air:
The goal should be to minimize the educators (the holes near the back) exposure to the surface of the water.

  • You can try rotating the nozzle so that one of the fins that separates the educator channels is pointed straight up. This sounds minimal but it sometimes is just enough to reduce the chance of a vortex forming.

  • Next -you can make sure the nozzle is parallel with the water surface. Again, this serves to push the educators just a bit further from surface.

  • Instead of parallel, you can also run the nozzle pointed slight upwards - like 5 degrees. In this case however, make sure you measuring the depth from the educators if you're worried about too much siphon back to the sump - since that's where the siphon will break.

  • The other suggestions such as drilling a small 1/16in hole in the underside of the Y or in one of the loc-line knuckles to break the siphon earlier is good. Also, reducing or adjsuting the flow rate (if you have a DC pump) just a bit can help as well.

Other things to keep in mind - if you run wave makers in your tank, the water level over the nozzle may not stay consistant since the wave may raise and and lower the water level as the wave travels across the tank. In this case, you'll need to account for the drop when deciding how deep to run the RFG nozzle.

Hope that help and if you anyone has any questions, please do not hesitate to ask.
 
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Mark Gray

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Interesting glad you posted this yes maybe I am too, tomorrow I will add a piece of lock line, I kind of thought it was my return lines sucking are I am running about 1000 gallons an hour, but I will give this a try

Thanks for posting
 

Mark Gray

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Interesting glad you posted this yes maybe I am too, tomorrow I will add a piece of lock line, I kind of thought it was my return lines sucking are I am running about 1000 gallons an hour, but I will give this a try

Thanks for posting
VCA told me about this and like I said I thought it was sucking air from my return line somewhere but I think it fixed it. I will post late tomorrow after I let it run 24 hours Thanks again
 

Bob Tiffany

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VCA told me about this and like I said I thought it was sucking air from my return line somewhere but I think it fixed it. I will post late tomorrow after I let it run 24 hours Thanks again

Mark, any update on your progress with this? I’m experiencing the same issues and was just wondering what your fix was.
 

Mark Gray

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Mark, any update on your progress with this? I’m experiencing the same issues and was just wondering what your fix was.
Man that was a long time ago. If I remember right I had to add a couple peices of the lock line and get them a little lower in the water. Love them though. They do a great job
 

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