Where the water line meets the edge of your pool, a dirty, dark line often forms. This is caused by organic or mineral dirt such as sunscreen, lime, etc., which settles there. You can solve this problem with the Waterline Cleaner, whether the pool is in use or not. Because of its gel form, the product adheres well to vertical surfaces.
It is best to vacuum the entire pool first and then backwash, which brings the water just a little lower. You can then easily apply the gel-shaped Waterline Cleaner and clean the liner or coping stone with a brush or microfibre cloth.
