Got stains in your hot tub? Well, there are three easy ways to remove them and you probably already have everything you need in your kitchen. For rust stains, rub with the solution of water and baking soda. For metal stains, use Vitamin C powder also known as a sorbic acid and for organic or debris stains, use diluted white vinegar. The easiest way to remove stains is to wipe down your surfaces after you've drained out your hot tub and remember that you only should be draining your spa and replacing the water every 3 to 4 months.