Safety pool covers can be a great choice when it comes to choosing a pool cover because it avoids the whole mess of he water bags, the duck pond hat winds up on top of the pool cover after a long winter, and most of all they are much safer then the traditional swimming pool cover.
Just like any other high end swimming pool product there is the goods and then you have the bad. The reason that the pool safety cover can be sagging is for a few reasons.
If the cover is just sagging by itself with no leaves , snow or debris on it that would mean that your loop loc cover is not properly adjusted or it could even be missing hold downs or anchors.
The first step would be too walk around the swimming pool and make sure that all the springs are connected to the anchors. If all the springs are connected to the anchors then you might want to loosen some of the cover straps with you bar and then tighten and reinstall them and your cover will be tighter.
If you have leaved and snow on your cover and its sagging big time, that would mean that the water in your swimming pool is to low. This can be caused by a leak in the liner of the pool or because the pool was improperly closed.
Many pool guys think that you have to drain huge amounts of water from the swimming pool when you really don't. You see the reason you would even drain any water from the pool in the first place is so that when it does snow or rain the drained water in the pool will make room for that new source since the safety pool cover is mesh. The downside to thinking and actually draining your pool 18" or more like some pool guys do because there lazy is so that they don't get a call in the winter from the how owner saying that there pool is over flowing. When in fact they should just tell the customer that they need to keep a pump handy just in case the pool water gets high.
The amount of water that should be drained on an in ground swimming pool closing is about 6 - 8 inches of water and no more, if you drain it any lower you pool cover will sag and then it could possible do damage to the cover or even the deck.