Submersible pump drawing air

[Hslobo]

Im trying to completely drain the pond to fix a leak and my submersible pump is drawing air as the water level drops below the pump itself. I think its coming from the faceplate that goes over the impeller as I just replaced the impeller and one of the screws just spins in place and wont tighten. IWas there a gasket of some sort that goes under the faceplate?

Any suggestions on how I can rectify this problem. its the mushroom factor, try and fix one problem and expose another. Thanks in advance for any info

 

[Tula]

If I'm understanding your description correctly, a submersible pump must be submersed to pump water. When the water level is too low, they will such air. I used to have to bail out the remaining amount with a small pan.

 

[Stephen Noble]

A couple of options...the @Tula bail out method which is 100% effective (I use that), get a cheap sump pump and it will get all but about an inch or so of water out or if your yard allows, use a siphon. But before continuing, could you share a little information about your pond? How large is your pond, is it a liner pond, preformed or concrete and is the leak on the bottom? Getting back to what @Tula suggested, there are benefits to just 'scooping' out the last inch or two of water and gunk.

 

[Hslobo]

It's pre formed, leak is transient occurring during winter due to contraction from the cold. When it warms up it will hold water. This has happened 2 straight winters now. I believe the leak to be on the bottom as it drains down to less than an inch in spots.

Has anyone used flex seal on this type of pre form? I'm questioning whether it would be toxic for fish

 

[GBBUDD]

I question if there is not just a vortex one that is creating like a tornado and your not seeing it and it draws in the air