Coverstar suggests, as all automatic cover manufacturers do, that you only cover pool water that you would swim in. If the water is temporarily out of balance due to chemical additive, covering the pool will shorten the life of the fabric. Use a good test kit frequently to maintain proper chemical balance. You must avoid a build-up of chemicals in the pool water that can result in serious damage to pool walls and equipment. Such build-up can also create an improper water balance which may cause deterioration of the vinyl cover. After adding any chemicals to your pool, allow the chemicals to circulate before closing the cover. If you are unsure if it is safe to close the pool cover, test the water at the surface with your test kit. Some pH adjusters may create harmful levels of alkalinity (high pH) if not allowed to mix with the water before the cover is closed. The same is true with chlorine shocks.
Some chlorine shocks require as long as 12-24 hours to return to swimmable range. Since safety is often the major reason people purchase a cover, we recommend the use of a non-chlorine shock. With this type of shock the cover may be closed in 30 minutes or less. Check with your pool service company for proper usage. The use of floating chlorine feeders is not recommended because they vent chlorine gas that can burn the cover fabric and often remain trapped in the same location.