Herbie drain won't siphon - air leak?

bronch · Oct 30, 2023

Hello everyone! First time reefer here, having some trouble with my new tank.

I decided to leak test everything before moving my aquascape into the tank but I simply cannot get my Herbie overflow drain to achieve full siphon. No matter what I do the drain shoots out a constant stream of rather loud air bubbles into the sump.

Using the gate valve, I have adjusted the main drain so that a small amount of water drips down the emergency drain. Even with the bulkhead completely submerged in the overflow, the primary drain still spews a stream of bubbles into the sump. I have also tried raising and lowering the flow rate on my return pump, turning the gate valve to match the increased/decreased flow, but it didn't solve the problem. Closing the primary drain completely (sending all water down the emergency drain) and then re-opening valve also did not work, and there were still tons of bubbles spewing out of the bottom of the drain even with the valve almost entirely closed and water pouring from the emergency drain.

I'm aware that it may take some time to purge air from my main drain and achieve full siphon, but the problem persists even after running the tank for ~3 hours.

I am also noticing a small "whirlpool" effect within the overflow located above the main drain.

I assume there must be some kind of air leak in my primary drain preventing the full siphon? I have slathered glue all over every joint on the drain but still the problem persists. Maybe the gate valve is leaking air? I have seen some people say 90 degree PVC elbows could be trapping air in the drain but my setup only has two 45 degree elbows on the way down to the sump.

My tank is ~50 gallons and my return pump is 800gph, if that matters.

Some pictures:

Any help would be appreciated...

Thanks!

BairCorals · Oct 30, 2023

Probably an air lock, try pulling the black pipe out from the sump water. Sometimes having the pipe submerged will keep that air locked in and won't allow a full siphon. Also, if you haven't already, try opening your gate valve all the way and see if it pushes the air out. Once the air is out, then adjust the flow

BairCorals · Oct 30, 2023

And welcome to r2r!

bronch · Oct 30, 2023

BairCorals said:
And welcome to r2r!

Thank you!

I suppose I could try shortening the black tube or running a new line down from the bottom union so that it terminates just below the waterline instead, but given that this black tube came stock with the sump I find it kind of odd that I can't find anyone else online having this issue. Wouldn't everyone have problems achieving a siphon if that black tube extends too far below the waterline? The sump is a Trigger Sapphire 26, by the way.

Opening the valve all the way to flush out air then closing it also has not worked.

Sisterlimonpot · Oct 30, 2023

BairCorals said:
Probably an air lock, try pulling the black pipe out from the sump water. Sometimes having the pipe submerged will keep that air locked in and won't allow a full siphon. Also, if you haven't already, try opening your gate valve all the way and see if it pushes the air out. Once the air is out, then adjust the flow

This.

If you terminate your pipe closer to the water line, you will be able to purge the trapped air easier.

The further down the pipe is, the increase of head pressure.

If you can get it to about 0.5‐1" below the surface, you should solve this issue.

bronch · Oct 30, 2023

Sisterlimonpot said:
This.

If you terminate your pipe closer to the water line, you will be able to purge the trapped air easier.

The further down the pipe is, the increase of head pressure.

If you can get it to about 0.5‐1" below the surface, you should solve this issue.

I removed the fitting that is screwed into the sump and only just now realized it's two pieces, not one long pipe...

Going to replace it with a shorter piece of PVC pipe and also glue it to the fitting, I guess? Maybe air has been leaking in through the seam.

I'm also realizing this drain pipe screwed into the sump has no teflon tape on the threads so maybe that could be allowing air in as well.

Sisterlimonpot · Oct 30, 2023

bronch said:
I'm also realizing this drain pipe screwed into the sump has no teflon tape on the threads so maybe that could be allowing air in as well

Are you talking about the union? That doesn't require Teflon on the threads.

BairCorals · Oct 30, 2023

bronch said:
I removed the fitting that is screwed into the sump and only just now realized it's two pieces, not one long pipe...

Going to replace it with a shorter piece of PVC pipe and also glue it to the fitting, I guess? Maybe air has been leaking in through the seam.

I'm also realizing this drain pipe screwed into the sump has no teflon tape on the threads so maybe that could be allowing air in as well.

Don't glue it, it won't spill anywhere. You can just cut the pipe smaller. Also don't use Teflon tape in the tank anywhere. It'll degrade and release into the tank over time, pipe putty works the best

BairCorals · Oct 30, 2023

Also you could just remove that pipe. Allowing a little bit of air agitating in the sump can raise your ph for free!

bronch · Oct 30, 2023

Sisterlimonpot said:
Are you talking about the union? That doesn't require Teflon on the threads.

Kind of hard to describe but this black bit goes inside the chamber beside the filter sock and screws onto threads on the bottom of the top black fitting. Not sure if air could be leaking in here either because there doesn't seem to be any kind of washer positioned on the bottom side.

I replaced the long black pipe with a smaller pipe so it now terminates a little less than 1" below the surface of the water now. Still have tons of bubbles and no siphon, but I haven't glued the piece of PVC to the fitting yet so that also might be the issue.

bronch · Oct 30, 2023

BairCorals said:
Also you could just remove that pipe. Allowing a little bit of air agitating in the sump can raise your ph for free!

Probably true but the sound of the bubbles rushing into the sump from the drain is extremely loud...

BairCorals · Oct 30, 2023

bronch said:
Kind of hard to describe but this black bit goes inside the chamber beside the filter sock and screws onto threads on the bottom of the top black fitting. Not sure if air could be leaking in here either because there doesn't seem to be any kind of washer positioned on the bottom side.

I replaced the long black pipe with a smaller pipe so it now terminates a little less than 1" below the surface of the water now. Still have tons of bubbles and no siphon, but I haven't glued the piece of PVC to the fitting yet so that also might be the issue.

Don't glue it, no need to. And you'll have to adjust your gate valve

BairCorals · Oct 30, 2023

bronch said:
Probably true but the sound of the bubbles rushing into the sump from the drain is extremely loud...

You'd be kinda surprised how quiet you can get it

BairCorals · Oct 30, 2023

The other thing you may need to do is lower the amount of water going into your tank, you may be pumping too much for your overflow to keep up with

EeyoreIsMySpiritAnimal · Oct 30, 2023

bronch said:
I am also noticing a small "whirlpool" effect within the overflow located above the main drain.

^^^This is the problem. The full siphon drain pipe is too high (or the water in the overflow box is too low...). If it's not far enough underwater, it will pull in air (the "whirlpool" you're seeing).

EeyoreIsMySpiritAnimal · Oct 30, 2023

bronch said:
I removed the fitting that is screwed into the sump and only just now realized it's two pieces, not one long pipe...

Going to replace it with a shorter piece of PVC pipe and also glue it to the fitting, I guess? Maybe air has been leaking in through the seam.

I'm also realizing this drain pipe screwed into the sump has no teflon tape on the threads so maybe that could be allowing air in as well.

Do not use Teflon tape. Use pipe dope.

EeyoreIsMySpiritAnimal · Oct 30, 2023

bronch said:
Kind of hard to describe but this black bit goes inside the chamber beside the filter sock and screws onto threads on the bottom of the top black fitting. Not sure if air could be leaking in here either because there doesn't seem to be any kind of washer positioned on the bottom side.

I replaced the long black pipe with a smaller pipe so it now terminates a little less than 1" below the surface of the water now. Still have tons of bubbles and no siphon, but I haven't glued the piece of PVC to the fitting yet so that also might be the issue.

The part with the threads is the bulkhead. Do not glue this. If there is not a gasket, it's possible that it could leak, but I doubt it's causing your current problem.

Sisterlimonpot · Oct 30, 2023

EeyoreIsMySpiritAnimal said:
The part with the threads is the bulkhead. Do not glue this. If there is not a gasket, it's possible that it could leak, but I doubt it's causing your current problem.

I tend to agree, the amount of flow that is needed to create a venturi is probably more than what can flow through that pipe using just gravity.

bronch · Oct 30, 2023

EeyoreIsMySpiritAnimal said:
The part with the threads is the bulkhead. Do not glue this. If there is not a gasket, it's possible that it could leak, but I doubt it's causing your current problem.

To be clear I was considering glueing the small piece of white PVC into the fitting, not glueing the threaded fitting onto the drain input bulkhead:

Still tons of bubbles and no siphon even with the smaller pipe terminating just below the waterline.

I'll take an updated picture in a bit once I have reattached the fitting.

Also, there whirlpool effect stopped after I raised the emergency drain pipe in the overflow. Still tons of bubbles coming out of the main drain, though, so I don't think it was related.