A common question among pool owners is, “Can I over shock the pool?” The short answer is no. You can add more shock than needed, which is a waste of money and materials. You can also get green hair from a reaction to high levels of chlorine. In general, however, over-shocking is harmless.
Treating your pool takes patience and a little know-how. While there’s no harm in over-shocking your pool, it’s important to use accurate measurements. Here, you’ll learn a bit more about shocking, how it works, what ratios to use, and the effects it produces.
What is Pool Shocking and How Does it Work?
Swimming pools, like all water vessels, develop bacteria and algae when left to their own devices. To kill this bacterium and make water safe for swimming, pool owners use a process called shocking.
Pool shocking involves adding high concentrations of chlorine to a pool at one time. This literally shocks the water and living organisms, killing bacteria. It is applied in a powder or solid tablet form of the chemical compound, calcium hypochlorite. It can also be added as a liquid mixture of sodium hypochlorite.
How to Mix and Apply Shock to Your Pool
Before adding calcium hypochlorite or sodium hypochlorite to your pool, you must first mix it with a minimum of five gallons of water. Adding the shock directly to the pool could damage the floor or lining of your pool. Diluting it is safer for your pool and for swimming later.
There is a bit of math in measuring your chlorine shock to water ratio. Your shock product likely has individual instructions based on brand and chemical ingredients. The common measurement for shock is 1ppm (parts per million) of change per 10,000 gallons of water.
To determine how much shock, you need for your pool, follow these steps:
- Find your combined chlorine by subtracting free chlorine from total chlorine.
- Multiply the combined chlorine figure by 10 and subtract your free chlorine from the answer.
- Determine the volume of your pool by using our pool volume calculator and divide the answer by 10,000 (based on the ratio of 1ppm per 10,000 gallons of water).
- Check your chlorine packaging to find out how much shock will produce 1ppm of change by 10,000 gallons.
- Multiply this number by the pool volume calculation you made earlier and the difference between combined chlorine divided by free chlorine.
- Divide your final answer by 16 to convert into pounds.
This tells you how much shock to use in your pool. Your package may also supply you with math-less instructions. An easy rule for the shock to water ratio (for liquid chlorine) is 2 gallons of shock product per 10,000 gallons of water. Standard chlorination only requires 1 gallon of shock per 10,000 gallons of water. The goal is to reach a level of 16ppm of change to shock the pool.
How to Test Your Water for Shock
After treating your pool, test the water to determine its effectiveness. You should wait one hour for every pound of shock treatment added to the water before testing. Waiting 24 hours is a good idea if possible. You may notice the water is cloudy after shocking, as pH levels regulate themselves, the water settles and clears.
Testing is accomplished with either a test kit or a test strip. Before testing, run your pump for 15 minutes minimum. The best time of day to test is early in the morning before the sun impacts the chlorination in the pool.
Follow these steps to test your water:
- Collect a sample from as near the center of the pool as possible.
- Dip your test strip into the sample water (If you have a test kit, add the test chemicals to the sample as instructed in your kit).
- Compare the strip, or sample color, to the color chart with your test gear.
Test strips may use different colors, but you ultimately want to see 1ppm as an indicator of safe chlorine levels.
Testing too early could give you a false reading. Test strips go white from bleach, leading pool owners to believe the water hasn’t received enough shock. This is one reason a 24-hour wait is optimal before testing.
Pool Shocking FAQs
Apart from, “Can you over shock your pool?” There are many questions pool owners have about the shocking process. Here are some of the most frequently asked questions.
How Often Should I Shock My Pool?
During peak swimming season in the summer months, you should shock your pool once every 2-weeks. Any other time of year (if you live in a city where it’s warm enough to swim year-round), you only need to shock the water once every 3 to 4 weeks.
You can tell when your pool needs to be shocked based on the chlorine level. Anything outside of the zone of 1 to 3 ppm requires a chlorine adjustment.
Do I Need Algaecide if I Shock?
Your pool may require algaecide if algae levels are higher than normal in your area. Algae grows for many reasons, including temperatures and debris falling into your pool. Shocking your pool should diminish algae and an algaecide shouldn’t be needed after a shock. However, some pool owners choose to use algaecide as an added safety measure.
Are There Certain Times my Pool Needs an Extra Shock?
Maybe. If you host pool parties or swim in large groups, the pH in the water could change. You may need to shock your pool after these events to regulate chlorine levels.
Similarly, if your city experiences intense weather patterns, it could cause additional dirt and debris to enter your pool. After cleaning the debris from your pool, shocking the water will regulate chlorine levels once more.
Should I Shock my Salt Water Pool?
Saltwater pools can be shocked, but the process is different. Your saltwater pool actually contains the same levels of chlorine as a chlorinated pool. The chlorine is just created and distributed differently, using a salt water system.
How Often Should I Test Pool Water?
You definitely need to test pool water the day after shocking it. Additionally, you should be testing pool water 2 to 3 times a week to ensure chlorine levels are maintained and are safe for swimming. Both low and high chlorine levels can impact your body, making skin itchy, irritating eyes, and causing a variety of other low-risk symptoms.
What is pH in Pool Water and Why Does it Matter?
pH levels measure acidity. pH is measured in many parts of your daily life. Food products are measured for pH, skin products are developed to balance pH, and pool products are designed to equalize pH in the water. When pH levels are too acidic, your water could be harmful to you and your pool surface.
Can I Under Shock my Pool?
Yes. You can under-shock your pool, and this is more problematic than over-shocking, but not a major issue. If you under shock your pool, the shocking process won’t work. Basically, your test will show your chlorine and pH levels are still off, and you’ll have to re-shock the water after letting it settle for a day. This can be a bummer if you’re planning a swim in the near future, but it’s not the end of the world.
To avoid under shocking your water, be sure to use the measurements we suggested above, and refer to your shock ingredient bag for specific shocking directions.
Tips for Pool Shocking
Now that you know you can’t over-shock your pool, here are some tips to streamline your pool shocking experience.
Shock Your Pool After Dark
We discussed the effects of chlorine in sunlight a little up above. Shocking your pool after dark is the best way to avoid UV degradation. UV light impacts free chlorine, rendering it less potent. When you shock the pool, you want to give it a real burst of chlorine. This is best accomplished without solar interference.
As a bonus, when you shock your pool at night, you might be able to swim in it the next evening. Otherwise, you’ll be waiting until the following day to take a dip.
Test Pump and Filter Before Starting Shock Treatment
When you shock the pool, you want to keep your pump and filter continuously going. This ensures chlorine doesn’t pool in one area. If chlorine isn’t evenly distributed in the pool, some bacteria will be shocked, while other bacteria live to see another day.
Test the pump and filter before you start your shock treatment so you know it will work efficiently during the process. You should keep the pump running overnight to maintain this even circulation. This speeds up the balancing process, making your pool safe to swim in sooner.
Consider Liquid Shock
While there’s no “right” kind of shock treatment, many choose liquid to avoid cloudiness. Both liquid and powder shock treatments work effectively to kill bacteria and algae. The powdered shock causes the pool to go cloudy until pH balance is restored. Liquid shock doesn’t have this effect.
Keep Your Pool Clean
You can minimize the amount of shock your pool requires by keeping your pool clean. Skim the pool regularly, wipe tiles or decking as needed, and ask swimmers to spray off before jumping into the water. Chlorine reduces the bacteria transferred from people into the pool water, but you can increase the efficacy of your chlorine by ensuring swimmers are clean.
So, Can You Over Shock Your Pool?
Not really. While there are some side effects to adding too much chlorine, including prolonged cloudiness or green hair, you can’t really over shock the water. Eventually, the chlorine and water will find equilibrium.
If you’re nervous you’ve added too much shock, keep your pump running and avoid swimming for a few days. Let the water settle, and test it twice a day in the morning and night until the reading gives you the green light to swim.
Pool owners can rest assured that adding too much or too little shock isn’t a deal-breaker. At most, you may have to wait or treat the pool again. If you follow the instructions on your shock packaging and test water before use, you should be just fine.