Opening a Pool, What Chemicals Are Needed?

Opening a Pool, What Chemicals Are Needed?

Spring has sprung and the temperatures are starting to rise. It must mean it’s getting close to the time to open your swimming pool for the season! And yes, it’s been a year since we’ve done this, so it may also be time for a refresher course on getting things up and running again. When opening a pool what chemicals are needed? In this article we’ll go over the chemicals you should have on hand and how they should be applied to get your swimming pool ready for another swimming season.

When Opening A Pool, What Chemicals Are Needed?

The main chemicals you’ll need to have on hand for your pool opening are: total alkalinity increaser, pH increaser, and decreaser, calcium hardness increaser, cyanuric acid, granulated chlorine shock, and chlorine tablets. Optional chemicals are pool clarifier and stain preventer. If you’ve never had a problem with algae before you could also skip applying an algaecide, but it still acts as good insurance against unforeseen circumstances.

Steps to Adding Pool Startup Chemicals

Following the correct order when applying pool start-up chemicals is important. It’s also important to allow the chemicals to fully circulate between applications to ensure that proper levels are maintained. This allows the next chemical application to work properly without being affected by leftover fluctuations from the previous step. After testing the water you’ll want to adjust the total alkalinity, pH, calcium hardness, and cyanuric acid levels, in that order. You’ll want the water to circulate for about six hours after adjusting the total alkalinity. Test it again to ensure the level remains stable before moving onto pH. Wait two to six hours after adding pH increaser or decreaser before testing again to ensure the correct range. From there you can move on to adjusting the calcium hardness with a waiting period of two to four hours and then cyanuric acid levels with a six-hour waiting period. As you can see, you’ll need to spend at least an entire day to apply all these chemicals. If you still have time, you can now add the stain preventers and clarifiers to allow them to do their work overnight.

Pool Shock

If you managed to get through your entire regimen on the first day, you can spend your second day preparing for shocking the pool. Check and clean your skimmer and filter baskets and get your pH towards the lower end of the acceptable range – about 7.2. It’s best to add shock in the evening as chlorine is sensitive to sunlight. This will allow the shock to work throughout the night and allow you to test the levels again in the morning. You’ll need to add one to five pounds of chlorine shock per 10,000 gallons of pool water depending on how clear the water is, to begin with. Make sure to pre-dissolve the powder in a bucket of water before adding the solution by slowly pouring it out while walking around the edge of the pool.


The use of an algaecide is not to kill already existing algae, it’s used to prevent it from growing in the first place. As mentioned, you may not need to use algaecide if you’ve never had problems with algae before, but all it takes is for a large storm, unusually hot weather, problems with your water pump, or an error when adding chemicals for algae to begin blooming. If the chlorine levels somehow drop to zero, algae can begin to bloom in mere hours. High chlorine levels reduce the effectiveness of algaecide, so you want to make sure the chlorine levels from shocking the pool have dropped below 3ppm before applying the algaecide. 

To learn more about inground pool maintenance, download a Backyard Escapes Guide.

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