Overflow Tuning Issue

[NotoriousENG]

Hi Everyone,

I noticed during leak testing this week that there is a bit of strangeness going on with trying to tune my overflow. The tank in question in s a 20 gallon long with a 10 gallon sumped powered by a Jebao DCP 2500 pump. The overflow box is an Eshopps eclipse S plumbed in a standard Herbie configuration with 1 inch PVC main and emergency drains. At low pump power (<40%) everything is fine, the overflow is very quiet and the water level in it is consistent. However, at higher pump levels (>40%) I am having issues with the inconsistent water levels in the overflow box. I am able to use the gate valve on the main drain to dial in the siphon rate so that there is just a trickle into the emergency drain. Everything seems to be good for anywhere from 10 minutes to an hour until the water level in the overflow box drops rapidly. If I let it keep running the overflow water level slowly creeps back up over the course of 5 minutes or so and is good for another half hour or so before it water level suddenly drops and the cycle starts over. Throughout this whole cycle, the water in the main display tank seems to be consistent so I am at a loss for what is happening.

I also have noticed a lot of splashing noise from the weir box at higher flow levels and am wondering if people have any suggestions on how to quiet it down.

 

[Mr.Shenanagins]

The main problem with the eclipse overflow is the difference in water level height in the tank and the overflow. The more distance the water has to drop, the noisier it is. I have my drain pipe quite high to combat this and mine is silent/near silent. The only reason you’d have a water drop is due to an interruption in the siphon or flow. For instance, when anything gets caught in the weir it will affect flow into the overflow. If you could send a picture of your overflow area and drains that would help, as well as the piping leading to your sump.

 

[NotoriousENG]

The main problem with the eclipse overflow is the difference in water level height in the tank and the overflow. The more distance the water has to drop, the noisier it is. I have my drain pipe quite high to combat this and mine is silent/near silent. The only reason you’d have a water drop is due to an interruption in the siphon or flow. For instance, when anything gets caught in the weir it will affect flow into the overflow. If you could send a picture of your overflow area and drains that would help, as well as the piping leading to your

I noticed that too. I have the water level right up to the included emergency drain stand-off at the moment. I was going to put a taller standoff in but noticed during clog testing (gate valve on main drain fully closed) that it's already so tall that at pump levels above 70% the overflow box floods since the emergency drain can't go full siphon due to drawing air from the surface. The overflow box really needs to be a few inches taller to allow a tall standoff that can still pull full siphon.

The weirbox shouldn't be getting clogged right now since the tank is empty with only water for leak testing. All in all a very confusing issue for me.

Here is the drains from the front. Both drains are 1" pvc. The main drain uses 4 45 degree elbows and the emergency uses two 90 degree elbows due to space constraints.

Here is the reactor and pump. The reactor is T'ed off the main line and uses two ball valves to control flow and back pressure. Plumbing is a mix of 3/4" vinyl tubing and 3/4" pvc.

Here is a full tank shot of the surface. The return is a hang-on back style using a split Loc line Y in the tank. I didn't drill the return in on this version of the tank since it lead to a crack on my version 1.

Here is the overflow box with the pump running at 40% (no issues at this level). The water level is a bit high right now since I'm getting more spillage down the emergency drain than I would like. The green sponge is a shrimp trap I am testing. The issue occurs with or without the shrimp trap so I don't think that is the issue.

 

[Mr.Shenanagins]

Please ignore the ugly algae and diatoms! The overflow faces a window. As you can see here my water level is much higher than than what it would be with that red pvc drain they provide.

 

[NotoriousENG]

Please ignore the ugly algae and diatoms! The overflow faces a window. As you can see here my water level is much higher than than what it would be with that red pvc drain they provide.

Do you issues with overflowing the box if the main drain clogs? I already can't run my pump flat out with the existing riser since it sucks to much air to pull full siphon. I would really like to use a taller riser like you are since I'm sure it would make the weir box way quieter.

Sent from my SM-G970U1 using Tapatalk

 

[Mr.Shenanagins]

No issues overflowing the box no, but I also have three drains. With your main drain wide open and pump full blast it will rise above your emergency drain your saying?

 

[NotoriousENG]

No issues overflowing the box no, but I also have three drains. With your main drain wide open and pump full blast it will rise above your emergency drain your saying?

With the pump full blast and the main drain closed (modeling a clogged drain) the water level rises so far its in danger of flooding the box. I think since the emergency drain is so tall it can't pull full siphon due to sucking air. Picture below is what I'm referring too.

The main drain can have the full pump flow with no problems. Even at max pump power I have to choke the main drain with the gate valve.

Sent from my SM-G970U1 using Tapatalk

 

[zozo]

The problem's cause and solution are rather simple... But not always that easy to explain in words what actually happens. If you would have used clear tubing you would see it, now you don't and have to imagine what happens in there. That's a tip I can give everybody building their first sump, use clear tubing.

But you have now is 1 piece of pipe from the overflow that goes submersed into the sump. Thus the only aeration this pipe has is the standpipe in the overflow.
What now happens is you fill this pipe up with water when the pump is running. Then the pipe also sucks in air bubbles, these bubbles get trapped into the water column in the pipe. Air bubbles want to float to the surface, but the falling water is dragging it down again. The air bubble grows bigger over time gets even more buoyant and it will be dancing somewhere in the middle of the route up and down in the tube. This is slowing the drain capacity down.

At one point it might shoot through or escape at the top it normalizes again but the process keeps repeating...

The solution is the drainpipe needs proper capacity and aeration to keep functioning at full capacity.

The other thing that actually makes absolutely no sense and makes the problem worse is the valve in the drainpipe. Why would you need to restrict its flow?
There is no need to do this. It should always be open at full capacity, it's the pump you should regulate with a shunt and a valve, not the overflow.

I'll try to make it more clear with a diagram. Below.

See? Divide the drain into 2 sections, the lower piece should be slightly bigger and aerated. In the sump put a T and a valve in the hose to the tank. With this valve, you can tune the water flow to the tank. The rest runs back to the sump.

Leave the overflow drain unrestricted there is non to regulate there. (I made it 25mm and 32 mm as example size it accordingly)

Below you see in a picture what I mean. Red arrow and open... It's the exact same principle overflow as yours just a Nano DIY version.

 

[Mr.Shenanagins]

https://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

This explains the purpose of the valve a bit more

 

[NotoriousENG]

@zozo Thank you for the informative reply! The reason the main drain has a valve is to restrict the drain in order to allow a full siphon to develop which is much quieter than running the drain open. Doing so with a single drian however, presents a flood risk, and thus a second drain is used that is unrestricted and run open to act as a backup in case the main drain clogs or is outpaced by the pump. I got this idea from reef forums where it is referred to as a Herbie style overflow and seems to be very common...

The gate valve only controls the main drain in order to develop a full siphon, the overall pumping rate is controlled by the pump controller which lets me vary the pump power from 30% to 100%. The main display tank level is fixed by the height of the weir box and is not adjustable due to the tank being drilled. There is a bit of variation in the water level depending on what power the pump is running but it is overall very small.

I am however wondering if trapped air in the main siphon drain may be the culprit of my cyclic overflow water level. On the reef forum, I haunt it was suggested to run the drain fully unrestricted for a half-hour to purge the drain before slowly closing it off till full siphon is achieved. I plan to give this a try and see if it helps.

 

[Mr.Shenanagins]

Your main drain in the sump shouldn’t go that deep, that is why your line isn’t purging! It should only be a few inches below where the sump max water level should be.

 

[zozo]

I am however wondering if trapped air in the main siphon drain may be the culprit of my cyclic overflow water level.

That cyclic level can only occur if the drain capacity is not constant. At one point it is restricted and the level goes up, once the restriction is gone the level goes down again.

I've had similar issues in the past, fortunately, I made my first from clear tubing and could see what happens in the tubes. And it was trapped air bubbles dancing up and down in the tube causing erratic drain patterns and hearing bubbles shoot through in the sump or burping and slurping noises at the top. Increasing the tube size and divide it into 2 sections where the last section functions as an open gutter. Made it running smoother and quieter.

Flood prevention is another very simple to achieve with a simple calculation. You should first calculate the volume you would need to flood the tank. That is the top rim glass to maximum water level. If your water levels 3cm from the top rim in a 100cm x 50cm tank that would make 3x100x50 = 15 litres

Now the pump is in the sump and if the drain blocks and the sump contains 50 litres of water with the pump on the bottom. Obviously, it will pump 35 litres too much to the tank and it will flood. Simply raise the pump on a platform so then it will run dry at less than 15 litres from the sump. Take a pump with a dry-running/thermal protection. This way it never ever can flood the tank.

https://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

This explains the purpose of the valve a bit more

Thank you, but still, the whole Herbie concept doesn't make much sense to me. I find it a tad over-complicated.

 

[zozo]

Your main drain in the sump shouldn’t go that deep, that is why your line isn’t purging! It should only be a few inches below where the sump max water level should be.

This actually doesn't make a difference, in both ways it will be submerged and closed at both sides, the top and the bottom. Thus the only aeration it has is at the top. Then if the pump capacity is rather too high the tube will kinda vacuum, then if an air bubble gets in it needs to travel all the way down to the sump. Small air bubbles slowly collect and gather and at one point it is big enough to restrict the flow through it constantly fights gravity because it is bouyant. Air wants up water wants down. And it actually doesn't need to physically suck in air, aquarium water is aerated and contains other gasses, it can and will degass in a drain pipe that is closed at both ends with water and actually the route it has to take is too long. It's a 24/7 process of flowing water that contains oxygen, CO², methane etc.

Not properly flowing drains that are not blocked have too little capacity or are badly aerated. This goes for sewages as well for sumps. That drain pipe is the aquariums sewage.

 

[NotoriousENG]

@zozo and @Mr.Shenanagins, Thank you both for the replies, I really appreciate all the information and advice.

I did end up cutting down the main drain so it doesn't extend as deep into the sump. I will try that and purging the main line before closing off the valve once the paint is try to see if that resolves the issue. If that doesn't, I might give the vented drain zozo suggested a try.

Flood prevention is another very simple to achieve with a simple calculation.

Thank you for the suggestion. I ran the calculations and to prevent flooding the display tank I would have to raise the pump to within an inch of the sump water surface. Being so close I feel like that would present a big issue for handling evaporation. With two drains and the sponge prefilter on the main, I'm comfortable with the level of risk of clogging a drian. However, clogging the weir teeth seems like a much more likely issue. Since the water level is quite high in order to have it above the bottom of the rim even installing a baffle near the pump likely wouldn't be enough to prevent flooding the display tank. One solution I am thinking about is to shave down the side edges of the weir box just enough so that if the teeth clog water can pour over the sides of the box before flooding the tank. Does anyone see any issues with this?

 

[zozo]

Good luck!... And we will see... It all comes down to the capacity of the drain pipe. To translate this into pipe size and gallon per hour is a rather complex theoretical formula. I don't want to say, nobody does this, all rather go with trial and error. Yet I've only found one article on the internet going into this and I skipped this part myself too and went on with experimenting. In the end, I changed my setup 3 times before I finally got it running smooth, quiet and safe.

And when I see this picture I see something obvious.

See the eddy at the top of the drain, the air column sucked in... This means you are running it at the edge of its max capacity the pipe is completely filled with water, both ends are submerged. All air bubbles sucked in have to get out somewhere. What happens to air bubbles trapped in the pipe I described above (the dancing ping-pong ball(s)). If you wait long enough you might hear blobs in the sump from bubbles shooting through.

And you describe you're experiencing it with erratic cycling/oscillating water levels in the box. I'm only using some logic here, as said above this can only happen if something is restricting the water flow in the pipe. And that can only be one thing if you are only sucking in water and air.

Sumps with drains are funny things, they work all with forces of nature the main force is gravity. And when it's not in sync water and air can play up in mysterious ways. All sumps are custom builds rarely you'll see 2 the same. All first builds will have their own issues to overcome. And it's hard to say what this all will be from a distance. It's often waiting for it and address it accordingly.

I had my first build run smoothly for several weeks and suddenly it started to play up in a similar way as you describe and I heard noises as bubbling, burping and gurgling. Then I had to stop the pump, drain the piping and start it over again. And it went on and on and it took days or weeks to act up again.

Anyway, there are 3 things to address these issues, this is lower the pumps turnover, increase the drainpipe size or increase the drainpipe capacity by venting it properly. In my case with venting, it worked a charm and it's running properly for over 5 years now.

Creating baffles in the sump can be a good idea... I designed my sump like this. It's a wet and dry concept. It has 3 trickle pipes trickling water over a sponge, it trickles down through the rest of the media and a perforated bottom and is polished by a second submerged sponge to the pump compartment.

The first compartment with the drainpipe is separated from the second with the pump. Water flows through the trickle pipes or over the baffle. Only the second compartment is affected and lowers its level by evaporation, about 1 litre per day.

This is my design, but there are many others out there.. Which is best? I can only say research as many ideas as you can find and make a pick that makes you feel best.

 

[NotoriousENG]

Well, I've been watching and the source of the problem is pump surging (or slight losses in power). I tuned it to have heavy flow down the emergency drain the lurked about to observe it. Water goes from heavy flow down emergency to none at all and slight drop in overflow box water height then back to heavy flow down emergency again. I can also see it in the amount of water coming through the weir teeth.

Outside of my return window on the pump so all around unfortuante.