Will Shocking Pool Lower pH?

Record has shown that it is good to shock your pool, at least once in two weeks. Pool shock helps to boost the free chlorine which destroys bacteria and microorganisms in your pool. You need it to swim in fresh and healthy pool water. But will shocking your pool lower the pH?

Yes, shocking a pool lowers the pH of the water, whether you are using chlorine-based or non-chlorine chemicals. You will need to take precaution because it isn’t good to swim in a pool with a low pH level since you would be risking your health and the pool surface.

After reading this post you will know how pool shock can lower your pool pH, the reasons and causes of low pool pH, and how you can remedy the situations. You would get all the information below.

Difference between pool shock and lower pH

Pool shock is the process of adding chlorine or non-chlorine chemicals to your pool to raise the free chlorine level in your pool water. On the other hand, a low pool pH is when the pool water is lower than the target pH range of 7.2 – 7.8. This simply means that your pool water is acidic and needs to be corrected.

Will shocking pool lower pH?

Yes, shocking your pool will lower the pH of the pool water whether you use chlorine–based shock like calcium hypochlorite or non-chlorine shock like potassium peroxymonosulfate. And because the pool water isn’t at the idea range it not safe to swim in it.

So, it is better to test the pool to find out its pH level after a shock. This will enable you to be sure that pH level of your pool isn’t too high or too low. Any number from 1-7 showing on your test strips means that your pool water pH is low. This can simply mean that the more chlorine used the lower the pH level.

How to shock your new pool

Causes of low pH after shocking a pool

  • The type of chlorine used

The type of chlorine one used can lower the pool pH. If chlorine-based product like trichlor powder is used, it will lower the pool pH. The rate at which the pH goes down will depend a lot on the volume of the pool and the amount of trichlor added. The general rule is that every pound of trichlor added to 10,000 gallons will lower the pH by 0.59.

  • Continued used of low pH chemicals

Experts are of the view that if one continues to use low pH chemicals, it can lower the pool pH after pool shock. If you continue using sanitizing chemicals that have a pH of 4 or less over time, the pool water will be affected. Chlorine tablets have a low pH of about 2.8-3.0, same with bromine which has 4.0. The continuous use of these chemicals will lower the pH of the pool.

  • Drop-in of rainwater after shocking

This mostly occurs with outdoor pools because they, even the ones covered, tend to have rainwater in them. If a pool is exposed to rainwater after a shock, then the pool water pH will be reduced. Rain picks up impurities from the air which may alter the alkalinity of the rainwater. As it falls into the pool water it lowers the pH.

  • Your local water source may have low pH

This might just be the issue with your pool after shocking it. The water you used might have been from a local water source with a low pH level. That is just it. This is why it is always good to test the water regularly to ascertain its pH level. You need to always have your test strip when operating a swimming pool.

What to do if my water pH is low after shocking?

If you test your pool water and finds out that its pH is low, the best thing to do is to raise the water pH before using the pool. The recommended level is between 7.2 -7.8. This is the ideal pH range of pool water that is safe for your health.

Why raise your pool water if it is low after a shock?

You should know by now that using your pool when the water pH is low will risk a lot of things, including your health. Low pH comes with its effects, so you need to avoid encountering these problems. Below are some reasons why you need bring your pool water to a balance;

  • To protect your pool equipment

If you let your pool water pH to remain low after a shock, you would be risking the pool metal surfaces such as pool cover components, light fixtures, ladders, screws, pipes, etc. Even your filter and pump could be damaged. Even a fireglass pool will be affected as there will be pitting, etching, and delaminating. The same will happen with a vinyl-lined pool, it will cause brittle and will later crack and tear. So, raising the pH will help you protect your pool surfaces from deteriorating.

  • To reduce contaminants in your pool

As earlier stated, with low pH water, the metal surfaces will dissolve and get damage. Where will all the debris go to? Of course, back into the pool water and your water becomes contaminated. Again, pool water can’t hold contaminants for a long time. Once the contaminants saturates the water, the metals will be dissolved and they will begin to reform on the pool walls. This will lead to stains and may clog the filters.

  • Better control of total alkalinity

Apart from balancing the pH level of the pool, another thing that needs balancing is the total alkalinity. But low pH level makes it difficult to control the alkalinity of the pool. The fact is that low pH will diminish the power of the chemicals that have been used to balance alkalinity. So, you need to raise the pH to control total alkalinity effectively.

  • Healthy pool water for a healthy skin

This is the most important reason why you should deal with low pool water pH after a shock. It is never advisable to use a pool with either high pH or low pH. Low or high pH levels may be harmful to swimmers. Acidic water will sting the eyes, turning them red, and the nasal passages will be affected. More so, the water will take away natural oils from the skin leaving the skin dry. This dryness in turn will make the skin itchy. So, raising the pH before use will make the pool healthier.

Remedy for pool low pH after shocking

The solution will be to raise the pH to the ideal level for a swimming pool. As already stated, the ideal pH range is between 7.2 and 7.8. So you need to first test your pool pH to ascertain the current level before raising it. The two easy ways to bring the pH to a balance are by the use of pH increaser (soda ash) or adding new water.

Using pH increaser

This is the general name for any substance that is used to raise the pH level of an aqueous solution. There are different names of pH increaser such as pH raiser, pH plus, and pH up. But the main pH increase for pools is soda ash. The following instruction should be followed with the use of soda ash:

  • The soda ash should contain 100% sodium carbonate. So, you need to read the label since different manufacturers might include different percentages in their products.
  • Using your test result, you should determine the quantity you would need to add. But it will good to go with ¾ % of any recommendation or use 4 pounds of it per 6 hours. You can keep on retesting until you are okay with the level. This is to avoid you adding too much and end up trying to reduce it again. Same with risking raising the total alkalinity if you add too much at a time.
  • If you need to dilute the soda ash, dilute it before using it.
  • Since soda ash comes in powder form, avoid using it where there’s wind to avoid getting it on your skin or clothes.
  • When using it, get close to the pool as it can easily be blown into the air by the wind.
  • Also, try to always add your soda ash near your pool water return jet. That’s where the water comes into the pool. This simply means that you need to avoid letting it in through water inlet sights or skimmer areas. It will help you avoid the risk of spreading it into the pool pump or filter.
  • If you have in-ground pools, it is advisable to dump the soda ash over the pool wall.
  • You might not need a pole brush since soda ash dissolves very fast. So, no need of worrying about spreading the substance around.
  • After using the soda ash in the water, you will need to wait for about six hours before retesting. But don’t wait longer than 24 hours.

Adding new water

Another way you can raise the pH of your pool water after a shock is by adding more water. Water from local water sources sometimes is slightly high in alkalinity. This is not how the pool water should be. This can bring down your pool water pH after a shock.

So, adding more water might just be the needed solution. You can test your water and add more water to balance up. Before testing the water, try to backwash your filter and then add more water. This can help to bring the pH up to the desired level.

How long does it take to adjust the pH in a pool?

It is always good to do a retest from 6 hours, but this depends on the soda ash added. If a large volume of sodium ash is added, it is better to wait for about 24 hours to retest the water. This will help you to determine the actual pH level of the water. But if it is just a little pH adjustment, one can swim in it after an hour.

Can you put too much baking ash in your pool?

Yes, you can put too much soda ash in your pool if you do not use the recommended dosage. Soda ash can help raise both the pH and alkalinity of the water, but using too much dose will lead to calcium buildup which may lead to maintenance issues. The pool water will become cloudy and the worst part is that it may clog the filter, rendering it ineffective.


It is always important to shock your swimming pool whether the newly opened pool or an old one. It helps to boost the sanitizer level – the free chlorine that helps to eliminate containments from the pool.

Unfortunately, this might reduce your pool pH which isn’t good for you. All you need to do is to raise the pH to its appropriate level. The two methods you can use to achieve this have been listed above.

So, you don’t need to worry if your pool pH drops when you shock your pool. The remedies listed above works well. You can try them out and stick with the one that works better for you.

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