Chlorine vs Non-chlorine Shock

To keep your swimming pool bacteria-free, you will need to add the right amount of chemicals to the water. Swimming pools are treated with chlorine tablets to provide safe swimming conditions, but chlorine can irritate the skin and eyes. You also have to wait 24 hours before entering a pool that has had a harsh chlorine shock, and the chlorine can still be intense over 24 hours later.

If you are sensitive to chlorine, you can do a non-chlorine shock of your pool, which will keep your swimming pool water clean while being gentle on your skin.

Different Types of Chlorine

First, you need to know the difference between free chlorine and combined chlorine. Free chlorine is the amount of chlorine that has not been combined with chlorinated water. Free chlorine is added to pool water to kill harmful bacteria and algae blooms. Combined chlorine is the pool water that has been mixed with the free chlorine.


When you smell a swimming pool that seems to be highly concentrated with chlorine, what you actually smell are chloramines. Chloramines are chemical compounds made up of nitrogen, hydrogen, and chlorine. Chloramines are formed when chlorine has mixed with common pool contaminants that contain nitrogen and hydrogen, such as urine, sweat, and skin cells.

Smelling chloramines within a pool means the chlorine is doing its job; however, you need to use more than just your nose to test the water. The buildup of these chloramines needs to be broken up through a process called chlorination. Chlorination is also known as shocking a pool.

How to Shock a Pool through a Non-Chlorine Shock

If your pool has built up too many chloramines, you need to shock your pool to destroy the buildup through oxidation. Shocking your pool with chlorinated chemicals can be harsh on sensitive skin even after the 24-hour period has passed. To protect your skin and eyes, you can do a non-chlorine shock of your pool.

1. Purchase a Chlorine-Free Swimming Pool Shock. To chlorinate your pool without shocking the pool with harsh chlorine, purchase a non-chlorine pool shock. Non-chlorine pool shock will raise the free chlorine levels by destroying the ineffective chlorine cells and chloramines through oxidation. Read the label on the shock for dosage information. This will be needed later.

2. Calculate the Volume of Your Pool. Knowing the total gallons of water in your pool will allow you to correctly calculate how much chlorine-free shock to use.

3. Test the Water. Using a chlorine test kit, take a reading of the free chlorine and total chlorine in the water to determine the amount of combined chlorine.

4. Get the Numbers. When you have your free and total chlorine amounts, you will need to do some math to find some very important numbers. We will use a 60,000-gallon pool in this example:

  • The first step is to find the combined chlorine amount. Take the total chlorine amount and subtract the free chlorine to find the combined chlorine amount. (2.3 total chlorine – 1.5 free chlorine = 0.8 combined chlorine)
  • Multiply the combined chlorine amount by 10. (0.8 x 10 = 8)
  • Subtract the original free chlorine amount from the above calculated combined chlorine amount. This will give you the desired change amount. (8 – 1.5 = 6.5 desired change amount)
  • Reading the label on the chlorine-free shock you purchased, find how many gallons is a recommended dosage. Divide your pool volume by the dosage volume. (60,000 gallons ÷ 10,000 dosage = 6)
  • Divide the desired change amount by the dosage parts per million (ppm) amount on the label. (6.5 ÷ 1.0 ppm = 6.5)
  • Find how many ounces of a chemical will produce a 1 parts per million chemical change. 1 pound of water is 120,000 gallons. Your pool is 60,000 gallons. (1 pound x 120,000 gallons = 120,000; 120,000 ÷ 60,000 = 2 oz of chemical to produce a 1 ppm chemical change.)

5. Find the Total Ounces. Plug in all the numbers from the above. You will need to multiply the ounces of a chemical by pool volume dosage by desired chemical change. (2 oz x 6 x 6.5 = 78 ounces)

6. Convert the Total Ounces into Pounds of Product. There are 16 ounces in a pound. (78 oz ÷ 16 = 4.875 pounds.) You will need approximately 5 pounds of shock for your 60,000-gallon pool.

7. Dissolve the Shock. If you need to dissolve your shock, fill a bucket ¾ full with warm water. Slowly add the amount of shock you need (5 pounds in our example), and stir slowly until the shock has dissolved completely.

8. Pour into Pool. Using your bucket of non-chlorine shock water, walk around the perimeter of your pool and slowly pour in the shock while continuing to walk.

9. Wait. You will need to wait for 15 – 30 minutes before entering the pool once the non-chlorine shock has been performed.

When to Do a Non-Chlorine Shock Rather than a Chlorine Shock

To maintain balanced chlorine levels within your pool, administer a non-chlorine shock to your swimming pool every week or two. This will make sure the free chlorine continues to kill bacteria as well as prevent algae from growing.

However, you will need to do a chlorine shock to your pool whenever the free chlorine level is below 1 ppm or if you will be experiencing any of these events: opening your pool for the season, attempting to kill recent algae growth, closing your pool for the season, or you are recovering from a recent large quantity of swimmers.

Performing a chlorine shock to your pool during this time will increase the free chlorine within your pool to give you safe and clean swimming conditions.

Maintaining your pool through routine non-chlorine shocks will help decrease the chloramines and increase the free chlorine within the pool. This will help keep your pool safe and clean without harming your skin and eyes!