Main Drain No Bubbles when closing pool

[digue]

Can anyone please help me diagnose, I've tried to close the pool, however when I tried to blow the main drain there is no bubble coming out from the bottom. I used a shop vac and there should be enough air blowed out.

Should I suspect any problems? if I leave the main drain like that for winter, will I have problems for extream cold icy days?

Thanks all.

 

[JamesW]

A shop vac won't generate enough pressure to blow out an 8 ft deep main drain. As long as the water in the pipe is pushed below the frost line, you should be fine. But, that's hard to verify.