Quote Originally Posted by MyBlueDog
Thanks.

Question for the engineers/scientists: Wouldn't a main drain suction blockage at 6' underwater, and a pump surface side 2' above cause the pump to pull oxygen from the water.

My thinking is since water contains O2, that any blockage in the main drain would restrict flow, causing the pump to work at the same rate, yet pull O2 from the water at a faster rate than it actually sucks the water.

Make sense?
I don't think you can "pull" dissolved oxygen from water with suction. If you could oxygen from water that easily, you probably would have been using a device that does that instead of a tank for your dives. (There are some devices for diving that allow you to extract breathable oxygen from water but I don't think the methodology is simple suction.)

Trying to think a little out of the box, is there any way you could drill a hole in the concrete chunk, insert a lead anchor, thread a lag bolt into the anchor, and pull the chunk out with a big pair of pliers?