Main Drain Air Pocket During Startup

[Steelcube]

I have two drains on my aquarium and I set up one to be a perfect suction to reduce the noise (pictured) but lately it seems like it has trapped air during startup that prevents it from draining. I have to manipulate the gate valve and it eventually passes. I'm looking for insight on how to fix it. My only idea is to shorten the distance the pipe goes into the sump. It's only 4 or 5 inches down though. Otherwise I may reduce flow because I noticed it started happening when I increased flow from the return pump.

 

[KStatefan]

Do not submerge the siphon drain over 1 inch

 

[Lost in the Sauce]

I have two drains on my aquarium and I set up one to be a perfect suction to reduce the noise (pictured) but lately it seems like it has trapped air during startup that prevents it from draining. I have to manipulate the gate valve and it eventually passes. I'm looking for insight on how to fix it. My only idea is to shorten the distance the pipe goes into the sump. It's only 4 or 5 inches down though. Otherwise I may reduce flow because I noticed it started happening when I increased flow from the return pump.

The 4-5" drains are about 3-4" too long. This is the reason you are having difficulty purging air out of the line.

 

[Steelcube]

Thanks for the advice. I trimmed it back and it works much better now. It still takes awhile to clear all the air so I may reduce my flow a little bit still.

 

[ZombieEngineer]

Have you tested a power outage on this and make sure you don't flood. Your drain configuration looks like it is going to put 1/4 of your tank volume on the floor.

 

[Steelcube]

Have you tested a power outage on this and make sure you don't flood. Your drain configuration looks like it is going to put 1/4 of your tank volume on the floor.

Yes, I initially noticed the issue after a water change. It hadn't happened previously so I was surprised. Fortunately the back up drain prevented an overflow until the main drain cleared. I bought this tank used and it had two separate 1" overflow drains until I converted one to full suction and left the other as overflow.

 

[Lost in the Sauce]

Yes, I initially noticed the issue after a water change. It hadn't happened previously so I was surprised. Fortunately the back up drain prevented an overflow until the main drain cleared. I bought this tank used and it had two separate 1" overflow drains until I converted one to full suction and left the other as overflow.

I believe @ZombieEngineer was referring to this drain. Without a siphon break, it'll likely pull water all the way down to the bottom.

A 3/16" hole here, should be enough to stop the siphon on power down.

 

[ZombieEngineer]

Your water level is gonna drop to here the way you have this setup as soon as your return pump shuts off.

 

[ZombieEngineer]

A 3/16" hole here, should be enough to stop the siphon on power down

Not if there is a snail on it during a power outage or return fail. Even then, it will still drain down to the low level of the bulkhead (similar to the way a herbie or secondary drain of bean animal works). That 3/16 hole only buys 1 extra inch at most if it's not covered by a snail or algae.

 

[Lost in the Sauce]

Not if there is a snail on it during a power outage or return fail. Even then, it will still drain down to the low level of the bulkhead (similar to the way a herbie or secondary drain of bean animal works). That 3/16 hole only buys 1 extra inch at most if it's not covered by a snail or algae.

An extra inch in the display, is Often much more due to a smaller sump. A siphon break is best practice. You could use it in conjunction with a check valve as well, But regardless of a snail existing in that exact time at the exact point of failure or not, It should be installed.

 

[ZombieEngineer]

An extra inch in the display, is Often much more due to a smaller sump. A siphon break is best practice. You could use it in conjunction with a check valve as well, But regardless of a snail existing in that exact time at the exact point of failure or not, It should be installed.

Agreed it better than nothing, but OP would be much better off rotating the whole fitting 180 degrees so it points up or even better installing an overflow weir. This would limit water drained to 1" above the top of the bulkhead rather than the bottom of it (with your hole suggestion) or 1" below it (left as is).

 

[Lost in the Sauce]

Agreed it better than nothing, but OP would be much better off rotating the whole fitting 180 degrees so it points up or even better installing an overflow weir. This would limit water drained to 1" above the top of the bulkhead rather than the bottom of it (with your hole suggestion) or 1" below it (left as is).

IF op had room to rotate it 180°, as a full siphon, I've got a feeling it would be creating a surface vortex and pulling air down into the tube.

 

[Steelcube]

There's a glass ledge above that would prevent rotating fully though even partially wouldn't be a bad idea. I have a hole drilled in the front though. I might add another after the comment about a snail potentially being on it or rotating it 90.