Robelle Winter Shock is a powerful oxygen-based oxidizer. When used regularly this product will help eliminate contaminants introduced by bathers and environmental factors like rain and wind. This product will not raise chlorine levels or produce combined chlorine. Robelle Winter Shock is gentle on pool surfaces. It dissolves quickly and will not bleach or fade vinyl liners or painted surfaces. Robelle winter Shock restores sparkle and clarity to pool water. Use Robelle Winter Shock: at initial treatment or at pool opening, weekly, after heavy user, after heavy rain or wind, or at pool closing. For weekly care, and after heavy use, heavy rain or wind. Add 1 lbs. of this product per 10,000 Gal. of pool water every week. Only use when no bathers are present. Bathers can return to the pool water after 15 minutes. Broadcast product uniformly over the surface of the water, adding 2/3 of the total dose into the deep end of the pool. Run the pool filter for 8 hours. For initial treatment, or when opening or CLOSING pools for the season, add 2 lbs. of Robelle Winter Shock per 10,000 Gal. of pool water. Public pools generally require more frequent doses of oxidizer than residential pools because they have greater bather loads. A dose of 1 lbs. of this product per 10,000 Gal. of water should be added each week. For initial treatment and during periods of hot weather or if bather load is heavy, increase treatment to 2 times per week.