When algae, bacteria, and other pollutants enter your pool, they affect the chlorine levels. Total chlorine might remain the same, but free chlorine will decrease while combined chlorine will increase.
The explanation is simple: free chlorine, which destroys contaminants, reacts with pollutants to form new bonds that give rise to combined chlorine. As a result, the combined chlorine will increase while the free chlorine drops.
To increase the free chlorine, you need to shock the water to break the chemical bonds and free the chlorine molecules. The free chlorine molecules are the active chlorine that destroys pollutants.
Moreover, the shock introduces new chlorine molecules into the pool water. So, it’s apparent that you can raise the free chlorine in your pool by adding shock to it.
How much shock do I need to raise free chlorine?
To raise free chlorine in your swimming pool, you need a DPD kit to test the water. The test will help you find out the amount of total chlorine and free chlorine in the pool.
With the test result, you will be able to deduce the amount of combined chlorine present in the pool water. If it’s higher than 0.2 ppm, then you need to shock the pool.
Combined chlorine = total chlorine – free chlorine.
But you need to know the right amount of shock to add to the pool. The target is to always raise the free chlorine to a point known as the breakout point. The value of the breakout point is the combined chlorine multiplied by 10.
If the combined chlorine is 0.7 ppm, you should raise the free chlorine to about 7 ppm. You can follow the calculation here to determine the amount of shock you should add to your pool.
If you still find it difficult to do the calculation, simply raise the free chlorine to 10 ppm and allow it to drop.
How do I make my free chlorine higher?
To make your free chlorine level higher, first, you need to raise the free chlorine level. Then you have to maintain the level by adding enough chlorine sanitizer.
Your chlorine sanitizer is absolutely important because bacteria and algae multiply rapidly. So prevent them before they invade the pool.
For the shock, you need to add enough shock to destroy pollutants. There are different shocks out there. If you have a limited fund, you can go for calcium hypochlorite.
Calcium hypochlorite is the cheapest chlorine shock. Using it means you need to add the shock more frequently because it dissolves very fast.
Furthermore, unlike other shocks like sodium dichlor, it adds calcium to the water, which might result in calcium build-up. Also, it doesn’t have a stabilizer, which is why it dissolves rapidly in water.
To keep your free chlorine high, your target should be to have enough chlorine in the pool. Achieving that requires regular shock treatment and enough chlorine sanitizer.
So, you need to test the pool regularly and shock it once a week. You can shock it once every two weeks if you don’t use it regularly.
Can you over shock a pool?
Yes, you can over shock your pool. That means having more chlorine molecules than necessary. Although the chlorine will deplete with time, you don’t want to expose your pool to excess chlorine all the time.
Do your best to avoid adding excess shock to your pool anytime you are treating it. This post will help you to know the right amount of shock to add to your pool. Too much chlorine can damage your pool components.
Even if you add excess chlorine shock to your pool you can rapidly deplete the chlorine by doing the following:
- Expose your pool to sunlight – Exposing the swimming pool directly to the UV rays of sunlight makes the chlorine molecules deplete faster. So, keep the pool open especially during the day.
- Heat the pool – Heat the pool also makes the chlorine molecules deplete. Some will escape with water vapor leaving the pool while the remaining are energized to react faster.
- Use chlorine neutralizer – Go to the pool stores and get a neutralizer. Using neutralizers works faster than the above methods. However, you need to be careful not to add excess neutralizer.
- Dilute the pool water – Drain some water from the pool and refilling it will help to correct the chlorine level faster. But this method might alter the chemical balance of the pool water. So, you need to test for pH and alkalinity after the process.
Why is my free chlorine so low?
Different factors can contribute to low free chlorine levels in your pool. Was there a heavy storm recently? Of course, if there was a heavy downpour, it would alter the chemical balance of your pool, including the free chlorine level.
Apart from rainfall, the following factors can contribute to the drop in the chlorine level in your pool:
- Pool Pollutants: Pool pollutants like ammonia can cause the free chlorine in your pool to drop. When chlorine reacts with ammonia, it forms chloramine. The chloramine formed is not an active bacteria killer because the chlorine molecule (combined chlorine) that reacted with the ammonia is no longer active. So, the reaction renders the chlorine ineffective.
- Heavy use: If your pool is regularly used by many people, there is a higher tendency for the free chlorine to drop. The organic matter from the bodies of the swimmers can react with the chlorine to form combined chlorine. And the more people you have in the pool, the more the chlorine level drops. This is why public pools are usually murky or cloudy.
- Sunlight and heat: The UV rays of sunlight help free chlorine to deplete rapidly. More so, heating the pool makes the chlorine react faster while some molecules escape with the water vapor leaving the pool water.
Can I add shock and chlorine at the same time?
No, it is not the right practice. You should not add pool chemicals at the same time. You might end up rendering the whole thing useless.
It is best to work with one chemical at a time. If you are trying to raise the chlorine level in your pool, start with a shock.
Shock your pool first and allow the level to drop to the recommended safe level of 1-4 ppm. Once the level stabilizes, you can add the chlorine sanitizer to maintain the level.
How long should you run the filter after shocking a pool?
After shocking your pool, you should allow the filter to run for about 6 to 24 hours, depending on the chlorine level after the shock treatment. But make sure you test the water before you start using the pool.
The time we stated above is for normal shock treatment. What if you are trying to clear a green pool? Well, it all depends on how many algae blooms your pool encounters.
To clear your green pool, you might need to run the filter for about 1 to 5 days. Using a vacuum cleaner and a clarifier can make the process faster.
Does shock raise pH?
Shocking your pool cannot raise the pH level of the water. It can only lower it, but the change is usually insignificant for pool owners to notice.
It’s normal because when chlorine reacts with water, it forms hypochlorous acid and hypochlorite. These compounds are acidic. Though they are weak acids, excess amounts can alter the pH level.
However, the pH level usually rises as the chlorine and its acidic ions deplete. So, it’s always difficult to notice the change.
How often should I shock my pool?
We have mentioned this before, but you should endeavor to shock your pool at least once a week. If you use it regularly, you might need to shock it twice a week.
But anytime there is a heavy storm, shock the pool. But test the water first to determine if it requires shock treatment. Another time to shock a pool is after heavy use, like a pool party.
If you notice algae blooms, shock the pool immediately. These factors determine when to shock a pool. But the general routine is to shock it at least once every week.
