PLEASE help me tune my overflow

[wsanley]

I need help tuning my overflow. I can't seem to get it right and was getting frustrated with it last night so I decided to just turn off the return pump for the night and try it again today.

Our 125gal display tank was not reef-ready so we purchased an overflow box (https://www.bulkreefsupply.com/eclipse-l-overflow-box-1000-gph-eshopps.html) and had our tank drilled for the box and returns. The box is rated for 1,000 GPH. We have the primary and secondary drains piped with down-turned elbows and small holes drilled on the top of each. The primary drain is maybe an 1/8" from the bottom of the overflow box, with the secondary drain approximately 1" above the primary drain. Both drains go to the sump, terminating about 1 1/2" below the sump water line into socks. The primary has a gate valve and is the only drain with a valve. The emergency drain is just a stand-pipe that is slightly higher than the top of the secondary drain, but not higher than the overflow box (it has a lid). We originally started out with a hole on the secondary drain only, then were advised to drill a hole in the primary as well. We also changed the height of our secondary drain to where it is now. We also added an airline to the hole that's drilled to the top of the secondary drain so when water rose in the overflow box it didn't create a full syphon in the secondary drain.

We have a LOT of flow into our return box. After watching some videos, it appears that this is not what you want and a steady, easy flowing, thin "stream" is more of what you want to strive for. With the amount of water we have in our system now, the depth of the water that goes through the weir is about 1/2". I'm not sure if reducing the amount of overall water in our system or using that ball valve to redirect some of the flow from our return pump is the best way to achieve the slower, steady stream.

When we tried to tune it in last night, we started with the gate valve on the primary drain only about 1/4 of the way closed and completely closed the ball valve for the pipe on the return line that went back to the sump. We closed the gate valve on the primary drain in small increments until the hole on the top of the primary drain in the overflow box was underwater, creating a full syphon. After a few minutes of the air purging from the system it appeared to be leveling out, but then a few minutes afterwards water would rise and then the secondary drain kicked in and would empty the overflow box. I observed most of this from the sump so I could tune it with the gate valve on the primary drain, which is about halfway between the display tank and the sump and is located on the section of the drain in our basement. Water was coming out into the sock primarily out of the primary drain, with some water and bubbles coming out of the secondary. Then, without being able to pinpoint why, water would rush into the secondary with a lot of bubbles for a few seconds, then the same would happen in the primary. Our flow rate from the return was about 670 GPH. I thought maybe this was happening due to too much flow coming from the return so we opened the ball valve a 1/4 turn to allow some of the flow back into the sump. This lowered the return flow to about 625 GPH. Fired it up again and it did the same thing, maybe even worse. At that point we shut it down for the evening.;Blackeye

 

[Ron Reefman]

Remove the elbows off one of the drains and if there isn't one already, install a gate valve. Set the top of that drain lower than the emergency drain.

Once you have it ready, run the gate valve wide open. Then slowly start closing it until the drain with the elbows starts to flow. You may have to play with the air hose in the top of the elbow, but not much. The gate valve does most of the work.

My tank during the test phase. The pipes turned out the sides are for return from the sump.

 

[Water Dog]

Judging by the water level in your exterior drain box, it doesn’t look like you have a full siphon. The full siphon (the shorter U pipe) line should be fully submerged. The water level also shows me that you aren’t even getting a trickle on the secondary drain. Also, you should move the gate valve on the full siphon closer to the sump. Where you have it, there still remains quite a long run going through a couple of elbows and that horizontal run, making it more difficult to prge out all the air.

How are you determining the 625 gph flow number back up into the tank? Are you using a Flowmeter to get that number? Based on the picture of the water levelin the external drain box, what should be your full siphon is only acting as a trickle so to speak. Once that ”trickle” of water reaches your overly restricted gate valve, that line starts to fill up. Once it’s full, the water level in the tank slowly rises. That excess water eventually raises the water level in the external drain box and that’s when the secondary drain gets triggered. Once that excess water is flushed out of the secondary, the process will slowly repeat itself. Open up the gate valve on your full siphon line as noted above and then slowly close it to achieve your full siphon. Again, it would really help to move that gate valvecloser to where the full siphon line enters the sump.

 

[wsanley]

Remove the elbows off one of the drains and if there isn't one already, install a gate valve. Set the top of that drain lower than the emergency drain. I'll remove the elbow from the primary. There's already a gate valve on the primary drain.

Once you have it ready, run the gate valve wide open. Then slowly start closing it until the drain with the elbows starts to flow. You may have to play with the air hose in the top of the elbow, but not much. The gate valve does most of the work. Yes, this is what we did last night. What do you mean by "play with the air hose on the top of the elbow? Do I need a valve on it?

 

[Jason777]

Adjustments need to be done slowly because once you close the gate valve enough to start raising the flow toward the secondary drain level it will most likely need to be reopened a little once it reaches the secondary and starts to "trickle". You have to sort of "creep up" on the secondary drain level. I remove the last piece of piping of the secondary drain in the sump so it's not underwater and that allows you to know exactly when the secondary drain "trickle" starts and makes it much easier. You also have a long run which will make it difficult because by the time the water from the secondary drain makes it to the sump the level has kept rising in the overflow at the rate you used to get it up to the secondary.

Once you get it tuned also realize that it will have to be changed every time you change flow rates.

The airline tubing you added to the secondary drain should not be to prevent it from achieving a full siphon. People usually add tubing there to help lessen the noise a little and to adjust the height where the full siphon occurs but you want it to go to full siphon should the level ever get that high.

 

[wsanley]

Judging by the water level in your exterior drain box, it doesn’t look like you have a full siphon. The full siphon (the shorter U pipe) line should be fully submerged. The water level also shows me that you aren’t even getting a trickle on the secondary drain. Also, you should move the gate valve on the full siphon closer to the sump. Where you have it, there still remains quite a long run going through a couple of elbows and that horizontal run, making it more difficult to prge out all the air. This is the water level with the return pump turned off. I just wanted to show how it's piped.

How are you determining the 625 gph flow number back up into the tank? Are you using a Flowmeter to get that number? Yes, there's a flow meter installed on the return line.
Based on the picture of the water levelin the external drain box, what should be your full siphon is only acting as a trickle so to speak. Once that ”trickle” of water reaches your overly restricted gate valve, that line starts to fill up. Once it’s full, the water level in the tank slowly rises. That excess water eventually raises the water level in the external drain box and that’s when the secondary drain gets triggered. Once that excess water is flushed out of the secondary, the process will slowly repeat itself. Open up the gate valve on your full siphon line as noted above and then slowly close it to achieve your full siphon. Again, it would really help to move that gate valvecloser to where the full siphon line enters the sump. I'll move the gate valve closer to the sump.

 

[Jason777]

Just to clarify, I remove the piece of pipe at the sump to make it easy to tune and once it's working I put it back on so it's back underwater and quiet. I just found that I couldn't tell when the trickle started while the end of the secondary was underwater and I was chasing the right level, which is what is sounds like you're doing.

 

[Mirkus]

did you get it fixed? i had an issue like yours when I first setup my overflow. The fix is quite easy... reduce the depth of your drain pipes into the sump. You said they were at 1.5 inches, make them .75. Also the hole in the top of your primary u drain makes it more difficult to start siphon.

 

[wsanley]

We got it fixed. I removed the last section of the secondary drain as suggested above and that helped immensely. We also rerouted some more of our flow from the return back to the sump and that helped with the noise from the flow to the overflow box being so fast. I took out the airline on the secondary drain as well.
Thanks for everyone’s help!

 

[Rylan5d]

Im running the exact same box. I tossed the elbow from the secondary drain, and just adjusted gate valve so water just trickled down the straight pipe. Silent, and haven't touched it in 4 months.