When you shock a pool you do not stick an electrical probe into the water to send a few thousand volts of electricity through the water. You add heavy amounts of concentrated chlorine to kill unwanted bacteria and algae. When you go to a pool supply store and purchase pool shock you will quickly understand that the cost of shock is far less than the basic chemicals commonly found in homemade products.
Determine the size of your pool in "gallons of water." The manufacturer of your pool can provide you this information if you do not already know it or if it is not listed in your owner's manual. The size of your pool determines how much shock you need.
Divide the total gallons of water by 10,000. Multiply that number by 0.5. In short, you need a half-gallon of chlorine bleach per every 10,000 gallons of water in your pool.
Remove the filters from your pool and pour the undiluted chlorine bleach into the water starting at the deep end. Allow the pool to run without filtration for 24 hours.
Pour in a chlorine neutraliser after 24 hours. Determine the pool's chlorine levels with a tester and bring the levels to within an acceptable parts-per-million (ppm) range of 2 to 4.