You may be considering using an in ground winter pool cover this year. It could be a great idea, but as with most things, there are benefits and drawbacks to the different types of covers. First, we need to be clear on what a winter pool cover is and what it is not, and second, you should have a clear idea of what your objective is in choosing a winter cover.
Pool covers for winter are primarily used to keep leaves, twigs and debris out of your pool and to keep your water and winter pool chemicals from evaporating throughout colorful chair covers the off-season. They are not pool safety covers because they do not meet the weight-bearing standards of the ASTM for safety covers. In fact, you should always have a pool safety fence in use if you are using this type of cover. Neither are they solar covers which are used during the swimming season for retaining heat in the pool, but do not keep out debris as well or deter algae formation.
Inground winter pool covers are made of polypropylene vinyl (solid) or polyethylene (mesh) fiber that is resistant to deterioration from the sun’s UV rays. Better quality covers are made from multiple layers of materials that add strength and deter the growth of algae. Once you put on an in ground pool cover, it generally stays in place until you reopen your pool in the spring. This type of cover is held on the pool deck using water bags (tubes you can fill with water and lay along the edge of the pool), Aqua Bloks or some other weight that will keep the wind from blowing the cover off and keep accumulated rain, snow, ice or leaves from sinking it. The cover then lies on top of the water, so it is below the level of the pool deck. They are available as solid or mesh covers.
The advantages of solid covers are that they keep the pool water clean through the winter season, prevent virtually all evaporation of water and chemicals and save time and money when you open the pool in the spring. They are relatively affordable and the better quality covers can last a long time.
The disadvantage is that solid covers are maintenance intensive. Because they are solid and rest atop the pool water, a reservoir is created where leaves, twigs and other debris will accumulate and where rain, snow and ice will be trapped. Throughout the winter standing water needs to be regularly removed using a pool cover pump. If it is not, the water and the accumulated debris can create a slimy mess that is dangerous to wild animals, pets and any creature that happens onto the pool. They may be unable to gain a foothold to get off of the cover and can drown. Furthermore, in the spring, this mess will have to be removed prior to taking the cover off or the weight of it will make it nearly impossible to remove the cover without dumping contaminated water into the pool.
There are two ways to avoid this maintenance headache. Adding a leaf net to the top of the solid cover will make it easier to remove leaves and other solid debris before it can begin to decompose. Simply lift off the leaf net, empty it and put it back on. You’ll still need a cover pump to remove the standing water and dirt.
The other alternative is to use a mesh cover. The mesh will allow water, snow and ice to slowly drain into the pool, keeping the leaves and other debris on top where they can blow away or be swept off. This makes winter maintenance and pool opening much easier tasks. A mesh cover, however, is not as effective at preventing algae, because it is not light-proof, or evaporation, though much of the evaporated water is replaced by the rain and melted snow and ice that drain through the cover. You will most likely have to do more chemical correction in the spring if you use a mesh in ground pool cover.