SLAM means 'Shock Level and Maintain.' SLAMing a pool is adding chlorine to your pool or spa to reach and maintain certain free chlorine (FC) shock levels to eliminate algae or ammonia. So you know SLAM is not a pool chemical.
There are no shortcuts to getting rid of algae or ammonia; the SLAM process requires patience, and results cannot be achieved in a single day.
You must add non-stabilized chlorine (Sodium Hypochlorite) in your pool at least twice a day for a couple of days or even longer to kill all algae.
Even worse, if you are fighting ammonia in your pool, measure the FC level every 15-20 minutes and add more chlorine when it reduces to some level. Ammonia has a high resistance to chlorine and consumes more of it when you start the SLAM process. The harder you hit it in the initial doses, the faster ammonia will go.
If you have been maintaining recommended FCL in your pool or spa by adding chlorine frequently, you don't need the SLAM process, unless you are sure you have ammonia or algae in your pool.
To achieve a successful SLAM in your pool, you will need liquid chlorine, which is non-stabilized chlorine, and an accurate test kit that can test high FCL.
Since the SLAM process involves testing FC levels and adding more chlorine in a swimming pool, you need to be aware of your Cyanuric acid (Cya) or chlorine stabilizer level so that you raise your FC level depending on the level of Cya in your water.
Remember, the higher the Cya level in your water, the more chlorine you will use to achieve the same effect, which is why we recommend non-stabilized chlorine for the SLAM process.
The recommended Cya level in a pool for a successful SLAM is between 30 ppm and 40 ppm; higher than that, you will have to spend more on chlorine to be able to clear algae or ammonia.
For instance, if your Cyanuric acid level is 30 ppm, the lowest for an outdoor non-salt water pool, the ideal SLAM level or FCL is 12 ppm, and the lowest FC level can go before adding more chlorine is 6 ppm.
This means you will add enough chlorine to raise your FCL to 12ppm and maintain it at that level by adding more chlorine if it reduces to 6ppm.
If your Cya level is 40 ppm, your shock level will be 16 ppm, and the lowest level free chlorine can go before adding more chlorine is 7 ppm.
Clearing algae or ammonia in a saltwater pool is even more difficult. Saltwater pools always need a higher Cya level between 70 ppm and 80 ppm, which will require more chlorine to raise and maintain the FCL at 28 ppm for 70 ppm Cya and 31 ppm for 80 ppm Cya.
If your Cya level is higher than 40 ppm for non-salt water and 80 ppm for a saltwater pool, it is advisable to lower your Cya by draining and refilling a portion of your pool or spa water before starting your SLAM process.
To understand the shock level to maintain in your pool depending on your Cyanuric acid level, refer to Chlorine/Cya Chart by trouble free pool.
Since clearing ammonia in a swimming pool or spa is more challenging and needs more initial doses of chlorine, after adding the initial chlorine to achieve your shock level depending on the level of your Cya, you will be measuring your FCL every 15-20 minutes every day and raising it back to your SLAM level by adding more chlorine. It may take a lot of chlorine and a few days to clear all the ammonia in your pool.
Just like clearing ammonia, clearing mustard or yellow algae may also require frequent water testing and the addition of more chlorine.
However, if you are fighting black or green algae, you can measure your FCL at least every 3-6 hours and raise it back to your shock level by adding more chlorine. Unlike clearing ammonia and mustard algae, removing green algae might require only two chlorine additions a day until you clear all the algae.