There are a lot of different factors that can contribute to unhealthy and unsafe pool conditions: heavy bather load, rainfall, organic contaminants, debris (examples include leaf litter or bird droppings). All of this can affect the balance of your swimming pool chemicals. If your pool looks cloudy, or if swimmers complain of irritated eyes or foul odors, then it is time to apply a pool shock treatment. Chlorine combines with debris to form compounds known as chloramines, which is what causes eye irritations and unpleasant odors. When you shock your pool, you are adding a super-dose of an oxidizing agent (in chlorine-based shock treatments, this would be chlorine, in non-chlorine treatments, this would be Potassium Monopersulphate). Shocking your pool raises the levels of free chlorine and unbinds the chloramines, clearing your pool and once again making it safe for swimming
First you need to determine the level of combined chlorine in the pool to help you calculate the correct dosage of shock treatment. You’ll need to measure the free chlorine levels in the pool and the total chlorine levels, then subtract one from the other. It is also important to know the size of your swimming pool (how many gallons of water it holds). After you determine these two numbers, you should be able to figure out how much shock treatment to add. Most products also come with a calculation table and specific instructions that should be followed.
Never add shock treatment to the pool when there are swimmers in the water, and only allow swimmers back in once the free chlorine has reached safe levels. With a non-chlorine shock treatment, the downtime tends to be less as opposed to a chlorine-based product. Another thing to keep in mind with non-chlorine shock treatment, you don’t have to worry about damaging or bleaching your pool liner or pool surfaces. Before you add the shock, it is important to check the skimmers for any debris and remove it. You should also remove any pool accessories from the water.