Can You Use Bleach to Shock a Pool?

  • By: John Parker
  • Last Updated: January 31, 2023

Pool algae can be a persistent problem for many pool owners, and many people turn to household cleaners such as bleach in an attempt to eradicate it. But does bleach actually work to kill algae?

If you have algae in your pool the way to kill it is by using chlorine shock. Bleach is basically a relatively weak chlorine shock solution so it will kill pool algae if a sufficient amount of it is used but it may not be the best idea.

In this article, we will be discussing the pros and cons of using bleach in a pool as an algae treatment, as well as exploring alternative methods for getting rid of algae in your pool.

Can you use bleach in a pool instead of chlorine

Table of Contents

Can you use bleach in a pool instead of chlorine?

Bleach is a chlorine solution so it has that in common with liquid chlorine you can buy in pool stores to shock a pool and get rid of algae.

Liquid chlorine is normally between 10% and 13% in strength. However, when compared to liquid chlorine, bleaches are normally a much weaker chlorine solution of up to 5-6% and even just 3% in some cases.

You can see then that you will need to use twice or even four times as much bleach to achieve the same results as liquid chlorine. That will often make it uneconomical to use.

Also, there is a possibility that particular types of bleaches will include some form of perfume which would obviously not be a great idea to add to your pool.

Can you use bleach to shock a pool?

As stated above, although bleach is a less concentrated chlorine solution than liquid chlorine, it can nevertheless be used as a pool shock. You will normally need to add more bleach to achieve the same results as you would using liquid chlorine.

How to use bleach to shock a pool

Fortunately, getting rid of algae is not rocket science, although it does require some time and effort to carry out the process properly. Removing algae can be done using bleach through a process known as shocking. 

Shocking means to increase the chloroine level in the pool temporarily to kill an contaminants, including algae. This is also known as superchlorinating.

To shock your pool properly, a series of steps must first be followed: 

Step 1: Check your water chemical levels

How to use bleach to shock a pool

The first step is to check the various chemical levels of your pool water. This is important as if you have improper water balance it can make the bleach ineffective at doing its job and killing the algae. This will only lead to a continuation of the problem and result in wasted time and effort. 

To check your water we recommend that you get a proper water testing kit (either a liquid test kit or test strips) which can give you a wealth of information regarding the state of the water in the pool. Good test strips such as the Aquacheck 7-way test strips that I use can tell you the total chlorine, free chlorine, pH, total alkalinity, CYA and hardness levels. 

AquaChek 7-Way Pool and Spa Test Strips - Silver Pool Test Strips For pH, Total Chlorine, Free Chlorine, Bromine, Alkalinity, Total Hardness, and Cyanuric Acid - Water Quality Testing Kit (100 Strips)

Check the pH reading

The ideal pH range is between 7.2 and 7.8. Outside this range can affect the ability of the chlorine to sanitize the pool water.

Chlorine reading

It is likely that when you check the free chlorine levels you will find that this is low. In this case adding bleach to shock the pool will increase it.

However, if the chlorine levels are high yet you still have a green pool then either:

  • you will see the total chlorine is high but the free chlorine is low. This will mean that the existing chlorine has combined with contaminants so it is no longer available to kill algae.
  • you may have plenty of free chlorine but the pH may have been outside the best range meaning the chlorine cannot work effectively. If this is the case then hopefully you will have now solved this problem by following the instructions above.

It is the free chlorine that kills the algae so you need to free up some chlorine. Read: Chlorine is high but my pool is green to see how to solve this.

Step 2: Brushing the surfaces

Can You Use Bleach to Shock a Pool - brushing

Although algae also floats in pool water, turning it green, algae cling to all surfaces of the pool such as the bottom, the sides, steps and pool ladders. These algae are more difficult for the chlorine to kill than the floating algae.

So to make life easier for the chlorine you should thoroughly scrub these surfaces with a pool brush, taking particular care in corners etc. This will put the algae into suspension in the water so that the chlorine when you shock can kill them.

Step 3: Adding the bleach

how to add bleach to a pool

Obviously you need to know how much bleach to shock a pool.

You should pour at least 2 gallons of bleach to the pool for every 10,000 gallons of water in order to try and kill the algae and get rid of your green pool water.

I always try and shock my pool in the evening and then let the pool pump run all night to ensure that the pool shock (bleach) is distributed around the pool evenly. Sunlight (UV radiation) degrades chlorine quite quickly so by shocking overnight the chlorine will have a better chance of working.

Step 4. Vacuum the pool

The next day, hopefully your pool will no longer be green. If it is then you need to repeat the shock treatment.

Assuming it is now clear you should see that there is dead algae on the bottpom of the pool (probably brown rather than green now). You will need to vacuum to waste in order to remove this algae dust.

Read: How to remove algae dust from a pool

Can you put bleach in a vinyl pool?

Bleach could potential damage your pool’s vinyl liner but only if applied directly to the liner. In that case the liner’s color may become bleached.

However, if bleach is simply added to the pool’s water then it will not cause any damage to the liner, unless you were to add a great deal of bleach of course.

How long after adding bleach to pool can you swim?

You should not swim in a pool that has been shocked with bleach for a minimum of 4-8 hours. You shoud check the chlorib¡ne level with a test strip and not swim until the chlorine level has gone down to normal.

Is chlorine and bleach the same thing?

Bleach contains chlorine in a fairly weak solution (3-6% chlorine) but liquid chlorine is normally at least double that in strength (12-13% chlorine).

Will bleach clear a green pool?

Since bleach is a chlorine solution then if adding bleach in a pool in the correct amount then it will help to clear a green pool.

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