Vinyl protectant’s have ingredients designed to protect your hot tub cover from the sun’s rays so that your spa cover will look great for many years. But beneath the vinyl, when conditions are right, mildew can appear on, or inside, spa covers.
The underside of the hot tub cover is made to withstand the harsh chemical environment it is exposed to but should be removed weekly from the spa to allow it to dry. It is also important to keep the hot tub water balanced, and, with proper sanitizer levels. These two things will inhibit growth of mildew on your spa cover. You should also leave the hot tub cover off the spa for a minimum of 30 minutes after you add chemicals to the spa to allow them to circulate through the water.
Most hot tub owners use their hot tub a few times a week which allows the underside of the spa cover to be exposed to air. If you do not use your tub as often, make sure to open the spa cover up at least twice a week and allow the hot tub cover, as well as the water, to breathe.
There is nothing organic in the spa cover to grow mildew, so if mildew does appear it is due to improper chemical levels or not airing out the hot tub cover enough. If you do get mildew, try swabbing the area with a vinegar/water solution leaving it off the spa to air out for a day.
In extreme cases, you should unzip the hot tub cover to allow cleaning inside of the fabric and of the foam core applying the vinegar/water solution internally. Stand the spa cover in an upside-down “V” shape on a warm and dry day to allow it to dry off.
With simple care and maintenance, you can further extend the life of your new hot tub cover.