Why is my Herbie overflow not pulling full siphon?

[ShanePike]

I can't get my Herbie overflow to pull full siphon, and I can't figure out why. I thought maybe it wasn't enough flow, but even ~600gph didn't change anything (except the amount of air bubbles). I also can't figure out where all the air is even coming from! I'm absolutely stumped.

Here's what it looks like running the Neptune Cor-15 return pump at 50% (which would be 750gph minus head pressure):

And here's what it looks like running it at 3% (45gph minus head pressure):

Here's how the overflow is set up:

And here's what my plumbing underneath looks like:

I know it would have been great to avoid that horizontal span as much as possible, but I read that a short one wouldn't make much difference. Plus, even if it did, wouldn't it just prolong the time it took to achieve full siphon? This thing ran for almost 24 hours and there was no change in the amount of air bubbles.

The gate valve is dialed in to where the water level is right at the top of the emergency pipe. (I get a trickle down it every time the powerheads make the water wave just a little too much.)

Every single joint is cemented thoroughly. Only the connections at the sump bulkhead aren't cemented. I did put a little caulk around the top (that's what the white stuff is) to see if maybe air was getting sucked in that way. It didn't make any difference.

I just can't figure out where that constant supply of air could be coming from. The DT and overflow are both 100% free of air bubbles.

I appreciate any wisdom you have!

 

[MnFish1]

I can't get my Herbie overflow to pull full siphon, and I can't figure out why. I thought maybe it wasn't enough flow, but even ~600gph didn't change anything (except the amount of air bubbles). I also can't figure out where all the air is even coming from! I'm absolutely stumped.

Here's what it looks like running the Neptune Cor-15 return pump at 50% (which would be 750gph minus head pressure):

And here's what it looks like running it at 3% (45gph minus head pressure):

Here's how the overflow is set up:

And here's what my plumbing underneath looks like:

I know it would have been great to avoid that horizontal span as much as possible, but I read that a short one wouldn't make much difference. Plus, even if it did, wouldn't it just prolong the time it took to achieve full siphon? This thing ran for almost 24 hours and there was no change in the amount of air bubbles.

The gate valve is dialed in to where the water level is right at the top of the emergency pipe. (I get a trickle down it every time the powerheads make the water wave just a little too much.)

Every single joint is cemented thoroughly. Only the connections at the sump bulkhead aren't cemented. I did put a little caulk around the top (that's what the white stuff is) to see if maybe air was getting sucked in that way. It didn't make any difference.

I just can't figure out where that constant supply of air could be coming from. The DT and overflow are both 100% free of air bubbles.

I appreciate any wisdom you have!

Unfortunately - can't see the videos - YouTube links are better for R2R if possible. where are the bubbles exactly in the tank?

 

[Dburr1014]

I can't get my Herbie overflow to pull full siphon, and I can't figure out why. I thought maybe it wasn't enough flow, but even ~600gph didn't change anything (except the amount of air bubbles). I also can't figure out where all the air is even coming from! I'm absolutely stumped.

Here's what it looks like running the Neptune Cor-15 return pump at 50% (which would be 750gph minus head pressure):

And here's what it looks like running it at 3% (45gph minus head pressure):

Here's how the overflow is set up:

And here's what my plumbing underneath looks like:

I know it would have been great to avoid that horizontal span as much as possible, but I read that a short one wouldn't make much difference. Plus, even if it did, wouldn't it just prolong the time it took to achieve full siphon? This thing ran for almost 24 hours and there was no change in the amount of air bubbles.

The gate valve is dialed in to where the water level is right at the top of the emergency pipe. (I get a trickle down it every time the powerheads make the water wave just a little too much.)

Every single joint is cemented thoroughly. Only the connections at the sump bulkhead aren't cemented. I did put a little caulk around the top (that's what the white stuff is) to see if maybe air was getting sucked in that way. It didn't make any difference.

I just can't figure out where that constant supply of air could be coming from. The DT and overflow are both 100% free of air bubbles.

I appreciate any wisdom you have!

Lots of bubbles coming out.
As it was running, did you slowly close the valve? That valve is used to tune it. Close it until a trickle of water comes out the emergency.

 

[Asm481]

You need the gate valve closer to the sump in that last vertical section. Air can build in the horizontal run and come out in tiny bubbles for a long time. With the valve close to the sump the bubbles, if any, stay out of the drain.

 

[Rjukan]

Is this diagram accurate? Your drain is at the bottom of your overflow?? Your sump holds all that water when your return pump is off?

 

[Rjukan]

Here's how the overflow is set up:

This is what I was talking about

 

[MnFish1]

I would want to make sure that the primary drain is not obstructed by something.

 

[ShanePike]

Sorry for the late replies! Been out of town. Thanks for the help!

I would want to make sure that the primary drain is not obstructed by something.

It's definitely not. Water is flowing fine.

Unfortunately - can't see the videos - YouTube links are better for R2R if possible. where are the bubbles exactly in the tank?

Zero bubbles in the tank; only in the sump coming from the primary drain line.

Lots of bubbles coming out.
As it was running, did you slowly close the valve? That valve is used to tune it. Close it until a trickle of water comes out the emergency.

Yes. The gate valve is dialed in to where the water level is right at the top of the emergency pipe. (I get a trickle down it every time the powerheads make the water wave just a little too much.)

You need the gate valve closer to the sump in that last vertical section. Air can build in the horizontal run and come out in tiny bubbles for a long time. With the valve close to the sump the bubbles, if any, stay out of the drain.

It's been running steadily for several days now, and the level of bubbles is consistent. It's pulling air from somewhere.

Is this diagram accurate? Your drain is at the bottom of your overflow?? Your sump holds all that water when your return pump is off?

It's not much water. The volume of the overflow is pretty small.

Right now, the only place I know isn't airtight is where the bulkhead attaches to sump. There is an o-ring on the top piece sealing it to the red acrylic, but the bottom piece is missing an o-ring. There is a fine seepage of water coming from there and dripping down into the sump. I need to get an o-ring for there and see if things become airtight then.

If not, I may end up having to remove the bulkhead altogether and just drop the pipe straight into the sump. We'll see.

 

[MnFish1]

Sorry for the late replies! Been out of town. Thanks for the help!



It's definitely not. Water is flowing fine.



Zero bubbles in the tank; only in the sump coming from the primary drain line.



Yes. The gate valve is dialed in to where the water level is right at the top of the emergency pipe. (I get a trickle down it every time the powerheads make the water wave just a little too much.)



It's been running steadily for several days now, and the level of bubbles is consistent. It's pulling air from somewhere.



It's not much water. The volume of the overflow is pretty small.

Right now, the only place I know isn't airtight is where the bulkhead attaches to sump. There is an o-ring on the top piece sealing it to the red acrylic, but the bottom piece is missing an o-ring. There is a fine seepage of water coming from there and dripping down into the sump. I need to get an o-ring for there and see if things become airtight then.

If not, I may end up having to remove the bulkhead altogether and just drop the pipe straight into the sump. We'll see.

However (and apologetically, I'm not sure I totally understand your sump set-up - but if water is leaking out - thats never good and agree you should fix - however, if water is seeping out, that also suggests that that is not the source of your bubbles.

 

[ShanePike]

However (and apologetically, I'm not sure I totally understand your sump set-up - but if water is leaking out - thats never good and agree you should fix - however, if water is seeping out, that also suggests that that is not the source of your bubbles.

Thank you! Turns out, I was wrong. Water is not seeping out of there once it gets going. I was wrong about that. The water I'm seeing dripping down the pipe is actually from a fine spray that is being caused by the air bubbles rising out of the water and popping. I couldn't tell that until I shined a flashlight at just the right angle to catch it.

I have tightened the bulkhead as tight as I dare tighten it (pretty good crank with a monkey wrench), and it is not airtight on the bottom part. When I first turn on the return pump, water seeps out from there until it gets going.

I took the union apart and checked it, and everything seemed fine. I also removed the grout where the pipe connects to the bulkhead and cemented it instead. Let it dry 6+ hours and turned everything back on. Nothing has changed. Still a significant, steady flow of air coming out the primary drain.

Tomorrow I think I'll see if I have some sort of gasket I can put between the lower part of the bulkhead and the rim of the sump. I can't think of anywhere else that air could be coming from.

 

[sfin52]

Thank you! Turns out, I was wrong. Water is not seeping out of there once it gets going. I was wrong about that. The water I'm seeing dripping down the pipe is actually from a fine spray that is being caused by the air bubbles rising out of the water and popping. I couldn't tell that until I shined a flashlight at just the right angle to catch it.

I have tightened the bulkhead as tight as I dare tighten it (pretty good crank with a monkey wrench), and it is not airtight on the bottom part. When I first turn on the return pump, water seeps out from there until it gets going.

I took the union apart and checked it, and everything seemed fine. I also removed the grout where the pipe connects to the bulkhead and cemented it instead. Let it dry 6+ hours and turned everything back on. Nothing has changed. Still a significant, steady flow of air coming out the primary drain.

Tomorrow I think I'll see if I have some sort of gasket I can put between the lower part of the bulkhead and the rim of the sump. I can't think of anywhere else that air could be coming from.

Try opening it all the way let it run like that and slowly start closing the valve.

 

[Dburr1014]

Thank you! Turns out, I was wrong. Water is not seeping out of there once it gets going. I was wrong about that. The water I'm seeing dripping down the pipe is actually from a fine spray that is being caused by the air bubbles rising out of the water and popping. I couldn't tell that until I shined a flashlight at just the right angle to catch it.

I have tightened the bulkhead as tight as I dare tighten it (pretty good crank with a monkey wrench), and it is not airtight on the bottom part. When I first turn on the return pump, water seeps out from there until it gets going.

I took the union apart and checked it, and everything seemed fine. I also removed the grout where the pipe connects to the bulkhead and cemented it instead. Let it dry 6+ hours and turned everything back on. Nothing has changed. Still a significant, steady flow of air coming out the primary drain.

Tomorrow I think I'll see if I have some sort of gasket I can put between the lower part of the bulkhead and the rim of the sump. I can't think of anywhere else that air could be coming from.

Where exactly is your gasket?

You should not glue your bulkhead.
Only a gasket is needed. The gasket should be on the flange side in the tank.

 

[bobbykoz]

Had similar issues in the past. Get rid of the 90s and do 2 45s. Also I understand people using those screen fittings but it’s restricting water flow. You already have a weir, the screen isn’t all that necessary but take that piece of advice with a grain of salt. But I guarantee the 2 90 bends are root cause. Water needs to flow in a smooth path not rush to a sharp bend, pick speed back up where the gate valve is and then hit another sharp bend.

 

[ShanePike]

Progress! I have determined where the air leak is. Now I just need to figure out how to fix it.

I decided to tape up every joint and wrap the union and gate valve in plastic bags and tape them off. Even though I had cemented every joint and sure hoped that the brand new union and gate valve were airtight, I wanted to be sure that no air was getting in.

Well, that made zero difference. The volume of air bubbles flowing out the primary drain didn't change at all.

At that point, the only two joints that I had not taped up were 1) where the bulkhead met the top of the rim of the sump and 2) where the bulkhead met the flange below the rim of the sump.

So I turned off the return pump so I could make sure those two places were good and dry. Then I taped them as well as I could. (The bottom one is incredibly difficult to maneuver tape around.)

When I turned on the return pump I saw a trickle of water from the underside of the bulkhead right where I had taped it up, so I knew I hadn't gotten it completely sealed.

However, once things got flowing there was a significant reduction in air bubbles coming out the primary drain. And when I placed my fingers around that seal to make it more airtight, the bubbles instantly decreased.

So it looked like the place I suspected all along really was the culprit, but I needed to be sure. So I removed the tape and bags from every joint, leaving just the taped up place below the rim of the sump. Zero change in the level of air bubbles.

Success!

TL;DR: I confirmed that the air leak is coming from the place where the bulkhead meets the flange below the rim of the sump.

Now the question is: How do I fix it?

• Find a gasket that will fit there? (I have one that's the perfect inside and outside diameter, but it's too thick. The threads on the bulkhead are barely long enough to connect with no gasket at all.)
• Put some grout around the edge of the bulkhead where it meets the flange?
• Put something else around the edge of the bulkhead where it meets the flange?

How do I create an airtight seal there?

 

[Dburr1014]

Progress! I have determined where the air leak is. Now I just need to figure out how to fix it.

I decided to tape up every joint and wrap the union and gate valve in plastic bags and tape them off. Even though I had cemented every joint and sure hoped that the brand new union and gate valve were airtight, I wanted to be sure that no air was getting in.

Well, that made zero difference. The volume of air bubbles flowing out the primary drain didn't change at all.

At that point, the only two joints that I had not taped up were 1) where the bulkhead met the top of the rim of the sump and 2) where the bulkhead met the flange below the rim of the sump.

So I turned off the return pump so I could make sure those two places were good and dry. Then I taped them as well as I could. (The bottom one is incredibly difficult to maneuver tape around.)

When I turned on the return pump I saw a trickle of water from the underside of the bulkhead right where I had taped it up, so I knew I hadn't gotten it completely sealed.

However, once things got flowing there was a significant reduction in air bubbles coming out the primary drain. And when I placed my fingers around that seal to make it more airtight, the bubbles instantly decreased.

So it looked like the place I suspected all along really was the culprit, but I needed to be sure. So I removed the tape and bags from every joint, leaving just the taped up place below the rim of the sump. Zero change in the level of air bubbles.

Success!

TL;DR: I confirmed that the air leak is coming from the place where the bulkhead meets the flange below the rim of the sump.

Now the question is: How do I fix it?

• Find a gasket that will fit there? (I have one that's the perfect inside and outside diameter, but it's too thick. The threads on the bulkhead are barely long enough to connect with no gasket at all.)
• Put some grout around the edge of the bulkhead where it meets the flange?
• Put something else around the edge of the bulkhead where it meets the flange?

How do I create an airtight seal there?

Where exactly is your gasket?

You should not glue your bulkhead.
Only a gasket is needed. The gasket should be on the flange side in the tank.

As I said, gasket, no grout? I think you mean RTV. No RTV. Doesn't matter how thick I guess it is long as you can thread the nut.

 

[ShanePike]

I had no idea RTV existed! Looks like that might be the ticket.

 

[Dburr1014]

I had no idea RTV existed! Looks like that might be the ticket.

No, I'm saying don't do RTV. It will fail at some point.
Gasket and only a dry gasket. OMG

 

[bobbykoz]

Yea man rip this out and redo it 100 percent.

 

[ShanePike]

It's working like it should now. All I had to do was seal the area where air was getting sucked in. Dead silent now.