Norwegian 530 gallon stainless steel

[keem]

No not the return. The overflow drains the tank too low. The problem is that my bulkhead pipes are 3" below my desired water level. I used a 45 degree elbow to get the correct water level. When i'm filling the tank, the water starts draining just before the 90 degree elbow connected to the strainer pipe. But when i shut the return pump off, the water siphons way lower, to the buttom of the bulkhead pipes. I drilled a hole on top of that 90 degree elbow, to prevent full siphoon on shut down, but that hole got clogged, and it drained way too much.
Complicated to describe, hope the pictures tell the story.

I have the second bulkhead with an elbow pointing upwards, for an emergency drain.

I can scrap the whole setup, if somewone suggest a better solution

 

[jjohnwm]

I'm not sure I am understanding this either. Are you using the elbow inside the tank to control the water level?

I also have a tank which has a side-drilled bulkhead that is just a wee bit lower than desired to keep the water level where I want it. In my case, it pours directly in a mechanical pre-filter that stands beside the tank, flowing from the bottom of that to the sump beneath the stand; I use a threaded union on the outside of the tank, which allows me to fine-tune the rotation of the elbow to adjust the water level in the tank up and down. It was easy to adjust and hasn't required required any attention since getting it set up. In your case, it might work but would require some re-working of your external plumbing, maybe replace the top part with some flexible hose to allow for adjustment of the elbow.

 

[TheWolfman]

I see what you mean now. A second hole and larger diameter holes would be the quick fix here the way you have it configured. Your especially running a durso stand pipe for your full syphon drain. This is why your having a hard time tuning the gate valve. Dursos aren't supposed to be restricted with valve but rather adjusted with the vents and airline tubing.They are one of the loudest drains, next to open channel.

 

[keem]

I can scrap the whole setup for better ideas

 

[TheWolfman]

Without adding a internal overflow box I don't see a way of reworking your current overflow. Did you drill the vent above the waterline? Because if it is drilled below the waterline the durso will go full syphon until it waterline drops below the vent hole flooding the sump.

 

[keem]

I drilled it below the water line, near the top edge of my strainer pipe. I redid the second drain, so the elbow is flush with the waterline and draining a small amount of water

 

[keem]

As long as my vent hole is not clogged, it works fine, not flopding the sump at shut down, but I have to check it now and then. Like i said, if the vent hole is clogged, it siphons the water waay too low (and flooding the sump)

 

[TheWolfman]

As long as my vent hole is not clogged, it works fine, not flopding the sump at shut down, but I have to check it now and then. Like i said, if the vent hole is clogged, it siphons the water waay too low (and flooding the sump)

Add a few additional vent holes, it can only help. I really like the way you have it setup. It actually takes the water from the lower part of the water, but still functions as a overflow and not a syphon.

 

[keem]

Is it ok to teach the urancopus and niger to eat at daylight? Ive seen them come out a couple of times during feeding, and i suppose they are not finding enoigh food at night, because of the rays enormous appetite

 

[TheWolfman]

I drilled it below the water line, near the top edge of my strainer pipe. I redid the second drain, so the elbow is flush with the waterline and draining a small amount of water

If I'm understanding this correctly the hole is below the water level? That's why your going full syphon on power loss. The hole needs to be above the water line to brake the syphon. Then the water will stop draining to the bottom of the elbow on power cut.