There are many ways to maintain a pool, you can do it manually by cleaning and filtering all the floating dirt on the water, use chemicals to keep the water clean, hire a maintenance person to preserve it regularly or either use or install pool covers.
Obviously, most owners maintain their swimming pools to get rid of the dirt and debris falling on it but in some countries, they have to keep it clean especially during winter when nobody is using the pool unless you want to freeze.
But which maintaining method should be used on winter? Of course, the pool covers. During the cold months, bacteria and other micro-organisms may grow and spread fast on cold stagnant water and that could be really dangerous.
Another thing, when it is winter then the pool is unattended and uncovered, there is a big risk for kids to fall on the pool when playing nearby and not supervised by any adult and will result to drowning. Pool covers are used to for protection and safety, not only from ailments caused by organisms on cold old water but also from drowning accidents that may occur.
Although some pool owners believe that it is better to drain and remove the water on their swimming pools when not used for a long time, still, it will not guarantee safety when left uncovered. Pool covers especially the automatic ones made of hard plastics also serve as safety cover even if the pool has no water.
Additional safety devices can installed at the pool area aside from the covers. You can put fence /gate and alarm system to detect if someone is on the pool to prevent fatal drowning that happens even in their own houses.