Is there any way to make a single bulkhead overflow with a strainer quieter?

[The Opinionated Reefer]

I put together a custom nano 45cm x 45cm x 45cm cube nano tank with a sump and it has worked out well apart from the drain.

The tank is an Amtra nano tank 90 and the stand is a red sea max nano stand. I got the tank drilled and a custom sump built for it.

I used the Lifeguard Aquatics 1" bulkhead as the main drain and then hard-plumbed it.

This here:

I used a 1" downpipe for better flow.

I know this type of overflow will never be totally silent as I have used it before but with flexible tubing. It was okay once the tubes slimed up. The issue I am having this time is that air seems to be getting trapped in the pipe and every so often there is a large belch of air that comes up through the main drain. The longer it's on the more frequent it becomes. When I used this same style of overflow in the past I used flexible tubing and although there were air bubbles coming out in the sump there was not this large belch of air.

So I wondering if there is anything I can do to make this quieter. Or at least get rid of the belching?

The last time i did this with the flexible tubing I put a tiny air hole on the U-bend out the back of the drain but this caused it to lose surface skim.

Here are pics of the setup

 

[The Opinionated Reefer]

Here's a video

 

[CBonito]

I put together a custom nano 45cm x 45cm x 45cm cube nano tank with a sump and it has worked out well apart from the drain.

The tank is an Amtra nano tank 90 and the stand is a red sea max nano stand. I got the tank drilled and a custom sump built for it.

I used the Lifeguard Aquatics 1" bulkhead as the main drain and then hard-plumbed it.

This here:

I used a 1" downpipe for better flow.

I know this type of overflow will never be totally silent as I have used it before but with flexible tubing. It was okay once the tubes slimed up. The issue I am having this time is that air seems to be getting trapped in the pipe and every so often there is a large belch of air that comes up through the main drain. The longer it's on the more frequent it becomes. When I used this same style of overflow in the past I used flexible tubing and although there were air bubbles coming out in the sump there was not this large belch of air.

So I wondering if there is anything I can do to make this quieter. Or at least get rid of the belching?

The last time i did this with the flexible tubing I put a tiny air hole on the U-bend out the back of the drain but this caused it to lose surface skim.

Here are pics of the setup

replace the elbow coming off the bulkhead with a tee, a short section of pipe that will go above the water line, cap it and drill a hole in the top of the cap. That will let the air in/out as needed to eliminate the noise.

 

[Wasabiroot]

There are devices called "Maggie Mufflers" that are fairly cheap and accomplish this, but I agree that drilling a hole may help. You can also try reducing flow to sump or adjusting return pump speed, but I'd be cautious unless an emergency overflow is present.

Maggie Muffler - Most innovative Aquarium Silencer Ever Made

It looks like you're in the UK though, not sure how that changes things.
It doesn't appear you have a valve down there though - ensure if you install one that it is a gate valve and NOT a ball valve as they are much harder to fine tune or adjust long term. I would strongly advise either an emergency overflow or changing your drainage to a "Bean Animal" or at least a "Durso" style overflow. Consider what happens if your main overflow becomes clogged - your return pump will continue to pump water into your display and empty your sump. This is essentially what is being described above.

 

[The Opinionated Reefer]

I ended up drilling a small hole in the u-bend in the pipe that leads into the filter sock and this stopped the belching. It's now much quieter although not totally silent. I'm not to worried about the drain clogging, I pay close attention to the tank and it would take a lot to clog it. I'll just live with some noise.

 

[Ben's Pico Reefing]

I agree what others have said. Replace 90° elbow with a t cap and you can even find some with screw on cap. You can drill hole and adjust as needed making hole bigger or tightening cap. You could also add airline tubing down pipe to allow air to freely escape where trapped.

 

[SteveMM62Reef]

Put a Piece of ABS Sheet above the Strainer to stop the Whirlpool. If the Strainer is at the water level, put a “T” Vertically in the Bulkhead Fitting, install a Strainer pointing down and one pointing up.