Overflow water level fluctuating with herbie drain

temple2101

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I just finished setting up an 80g tank that has an overflow with a 1” and 3/4” hole in the bottom. I used the 3/4” for the main drain with a gate valve and the 1” for the emergency drain. I’ve been wrestling with maintaining a consistent water level in the overflow. It will lower below the emergency drain and then eventually rise to a bit more than a trickle into the emergency. Then it repeats over and over…

I’ve been reading and thinking and I’m wondering if it’s air in the full siphon. My sump has 2x 1” bulkheads. I used a reducing coupler from the 1” bulkhead to the 3/4” pipe from the drain. I’m thinking that may have been a bad idea now. could that be the cause?
 

John08007

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You only put a valve on the full suction, the emergency drain is higher. I think my emergency is about 1" below the top of the overflow. It took a bit to dial it in but I slowly tweaked the valve shut till just a trickle goes into the emergency drain.
 

DeepintheReef

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Your return pump just needs to be turned down or you need to open the main drain gate valve slightly
 

JumboShrimp

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No, I follow you. A valve on the emergency is more of a convenience for initial set up, cleaning, etc., and occasional tweaks. But for any drain, a gate valve will allow much more subtle adjustments than a ball valve— that was the main thing I wanted to be sure you knew. :)
 
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temple2101

temple2101

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Gate valve is only on the main (3/4”) drain. I’m running 2 return pumps, both Jebao DCP-4000 with 1 on the lowest setting and the other (through UV) on the 2nd lowest. I have a flow sensor on both but haven’t hooked them up yet. Here’s a pic of the setup almost complete.

F5770EFF-578E-4B5F-8249-4CED6B9D1B98.jpeg
 

Shirak

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When it drops on the low side is it sucking any air in like a whirlpool effect? If so it could be slowing the syphon and causing the overflow to rise which will then force the small amount of air out once it gets high enough to put a but more pressure on the syphon.
 

John08007

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Maybe turn one of the pumps off and see if you're able to get it tuned and then turn off that pump and try it with the other. I am thinking maybe one of the pumps are not pumping a consistent amount.
 
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temple2101

temple2101

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Thanks for the replies so far! I’m hoping to get my flow sensors going today to see where I’m at there. I’m also going to try starting over on my full siphon and opening the gate valve all the way and then dialing it back in. Will also try with 1 pump on at a time if needed. I haven’t timed it yet, but the up and down cycle seems very consistent (maybe every ~2 minutes).

No one has commented on the reducing coupler, so I assume no one thinks that could be the cause?
 

JumboShrimp

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I have reducing couplers on my 3-drain system; with or without they you should be able to tune things in / reach the state of equilibrium you’re seeking. Keep up the good fight! :)
 

Shirak

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Not sure what reducing coupler your talking about but if you need to close the gate valve on the main drain to slow the flow and keep water in the overflow then there is no problem there
It usually takes a minute for air to completely purge from the main drain to create a steady siphon. If some air is getting sucked in periodically afterwards it will change the siphon flow and mess with the level in the overflow until it is purged again.
 
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temple2101

temple2101

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OK, I think I found the issue. I have a Nero 5 on the opposite end of the overflow pointed towards the overflow (4 foot tank). It's on random mode right now set to 85% max. When the flow goes somewhere over 2000gph is when I notice the water level change and the sound of the water falling over the overflow gets louder. So given that, I assume I should tune the drain to trickle at the "max" level the overflow gets to?
 

Shirak

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Not sure I would really worry too much if the level in the overflow goes up and down slightly. Even a the occasional trickle down the emergency drain shouldn't be an issue. As long as you are keeping a full syphon going on the main drain so that it doesn't suck air and get noisy and cause a lot of bubbles in the sump.
 

nereefpat

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OK, I think I found the issue. I have a Nero 5 on the opposite end of the overflow pointed towards the overflow (4 foot tank). It's on random mode right now set to 85% max. When the flow goes somewhere over 2000gph is when I notice the water level change and the sound of the water falling over the overflow gets louder. So given that, I assume I should tune the drain to trickle at the "max" level the overflow gets to?
I was going to ask about powerheads.

If you don't want any noise from the trickle/emergency, then you'll have to do it like you say in your last sentence, or even set it lower. If you don't mind a little noise, you can set the level a little higher.
 
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