Herbie main drain noise

[RandomFactoid]

Hi all,

I recently bought a 2nd hand Aqua One 120Liter tank with a sump. It's my first sumped tank. It came with a Durso standpipe. Having done some reading, I've decided I want it quiet and drilled a 3rd hole in the weir. Everything seems to function well, however I am not getting air expelled from the drain pipe fully, resulting in bubbling. I think the air's trapped right under the Spears gate valve.

Video here:




Any ideas ?

 

[vetteguy53081]

I took best pic I could. I placed a pvc cap on mine and drilled a hole and siliconed a rigid tube to the hole and now dead silent

 

[RandomFactoid]

I took best pic I could. I placed a pvc cap on mine and drilled a hole and siliconed a rigid tube to the hole and now dead silent

Thanks for the reply. I'm not sure if we're talking about the same issue. The bubbling I'm getting is where the main drain goes into the sump. Feels like the air trapped in and below the valve just doesn't get expelled

 

[RandomFactoid]

Thanks for the reply. I'm not sure if we're talking about the same issue. The bubbling I'm getting is where the main drain goes into the sump. Feels like the air trapped in and below the valve just doesn't get expelled

I can't edit my 1st post anymore, but Ive converted the overflow to a Herbie style

 

[KStatefan]

How far below the water line in the siphon line?

 

[RandomFactoid]

How far below the water line in the siphon line?

1-2cm

 

[RandomFactoid]

This got me thinking. Is it possible that due to a not-so-big tank size, the amount of water that goes down the weir (pump is 1000L/h) is not enough to create fast enough flow through a ~35mm ID pipe (which is big for such a flow, hence I need to close the valve quite a bit, hence the flow velocity under the valve ends up being quite slow and air gets trapped ?
Which would lead to a thought that perhaps I need to use a reducer under the valve and reduce the diameter of the pipe to gain faster flow ?
As per this equation

...or am I overthinking this ?