It sits on top of our pool cover. If you have a really sturdy pool cover, I would think it would be ok. It weighs approximately 13 lbs. It works GREAT for us.
#4 Can i leave it on the pool cover in the winter?
I didn’t leave mine on the cover during the winter. But I believe you can only thing is if it is too cold water will freeze inside the unit and will have to wait until it defrosts to pump the water out. I only used mine when the water wasn’t frozen.