How to SLAM a Pool

When summertime hits, the word “SLAM” might become a buzzword among pool owners in your neighborhood. You’ve likely gathered that people SLAM their swimming pools to sanitize them, but you’re probably wondering just how effective SLAMing is.

I’ll walk you through everything you need to know about SLAMing a pool and how to do it.

What Does it Mean to SLAM a Pool?

SLAM is an acronym that roughly outlines the process it involves. It goes as follows:

S: Shock

L: Level

A: And

M: Maintain

The idea behind SLAMing is to shock your pool with a greater concentration of chlorine than standard pool shocks. By doing so, you’ll eliminate algae, viruses, bacteria, and organic compounds that are a nuisance to swim with at best and dangerous to your health at worst.

Let me establish this from the start — you should put careful thought into deciding whether to SLAM your swimming pool. It requires a high level of chlorine, which can irritate your skin and respiratory system.

Nevertheless, SLAMing is a good choice under circumstances where regular shocking isn’t keeping your pool clean. For example, you may notice algae bloom in your pool, or the combined chlorine level becomes too high.

The good news is that regardless of your pool’s material, you can SLAM it.

SLAMing vs. Traditional Pool Shocking

There are two main differences between pool SLAMing and shocking: The time it takes and the amount of chlorine you use.

Time

Whereas you can shock a pool overnight, SLAMing a pool requires a larger time commitment — anywhere from a few days to weeks. Furthermore, you’ll need to constantly add free chlorine to your pool to keep the water in an active state of oxidation.

Part of the science behind this is that the sun destroys chlorine’s oxidizing properties. In fact, if you add chlorine when the sun is out, it could lose up to 90% of its potency after two hours.

Therefore, when you have a severe alga, bacteria, or organic matter issue in your pool, the constant addition of chlorine better fights them off.

Amount of Chlorine

SLAMing your pool water is a financial investment in addition to a time investment since you’ll need to purchase more chlorine than a regular pool shock.

The idea with SLAMing is that you never let your pool water come out of its shock level. Therefore, you’ll not only need to purchase enough chlorine, but you’ll also need to test it frequently to ensure that the water remains shocked.

By inundating your pool with large quantities of free chlorine, it’ll lower the water’s level of dangerous combined chlorine in addition to bacteria, viruses, and algae.

How to Prepare to SLAM Your Pool

After you do your research and decide that SLAMing your pool is the right fit for you, it’s time to prepare. First, purchase plenty of chlorine and shock test kits at your pool store.

Then, assess your pool. Take a look at the pump and make sure it doesn’t have any leaks or wear that could break down during the SLAM; you’ll need to leave it running the entire time you SLAM your pool.

If you have close neighbors and a loud pump, you might want to see if there’s anything you can do to reduce the noise.

Next, to give your chlorine more time to tackle the major issues in your pool, such as algae and bacteria, skim out all debris. Empty your skimmer baskets, too, and make sure you keep them clean during the SLAM.

The reason it’s so important to remove all visible organic matter is that the more chlorine has to work to break down these particles, the quicker it’ll lose its effectiveness.

The last step in preparing to SLAM your pool is using testing strips or a digital test kit to determine the following levels in your water:

  • pH
  • Cyanuric acid
  • Free chlorine

Because it’s so critical to have a correct reading on the free chlorine level, I recommend using a FAS-DPD chlorine test.

How to SLAM Your Pool

Luckily, slamming your pool isn’t hard. However, it’s important to choose a time to do it when no one plans on swimming in your pool. Otherwise, the high chlorine concentration could cause skin irritation or burns, respiratory issues, and even chlorine poisoning.

So, send your kids off to your neighbor’s pool that already went through slamming so that you can get started on these steps.

Step 1: Get Your pH Level Straightened Out

You likely spent the summer working hard to keep your pool’s pH level in check, so what I’m about to tell you to do might come as a surprise — you need to get your pool out of the 7.4 to 7.6 range and down to a pH of 7.2.

Go ahead and grab some pH reducer from your pool store if you don’t have it on hand already, and follow the instructions until your water tests at the 7.2 mark.

If you go overboard with adding the pH reducer, you can always raise the pH by adding a little baking soda or soda ash to your pool.

The reason that it’s so important to lower the pH level before you start your SLAM is that the high chlorine concentration will throw off pH testing kits during the treatment.

Step 2: Take a Look at The Cyanuric Acid Level

The layman’s term for cyanuric acid is a pool stabilizer. But whatever you call it, the important thing is that you get the levels to a range between 30 to 50 parts per million (ppm).

Here’s some good news: A 30 – 50 ppm range is the amount of cyanuric acid your pool should have regardless of whether you’re performing a SLAM.

If the cyanuric acid level is too low in your pool, add a pool stabilizer to the water to bring it up. Alternatively, if the cyanuric acid level is too high, you’ll need to add more water to your pool, diluting it until it falls into the ideal range.

Step 3: Pour in Chlorine

With the pH and cyanuric acid levels in check, it’s time for your SLAM party to begin. You’ll need to determine how much chlorine you need to add to your pool during the SLAM, which you can select based on the cyanuric acid level of your water.

To give you a base to work with, the free chlorine of regular pool water should be anywhere from 2 – 4 ppm.

Below are the estimated calculations you can use to determine how much free chlorine you should add according to the amount of cyanuric acid in your pool.

Cyanuric Acid (ppm) SLAM Free Chlorine (ppm)
30 12
40 16
50 20

Technically, you can SLAM your pool if it has higher levels of cyanuric acid. However, you’ll end up spending even more money on chlorine, and you won’t be doing your pool a favor since you’ll ultimately need to get the cyanuric acid level down to 30 – 50 before you swim in it.

Step 4: Keep Adding Chlorine

That’s right — your most important job from here on out is to regularly test your pool water to ensure it maintains the correct amount of free chlorine according to the chart in step #3.

I recommend testing your pool every two to three hours when you first start since the bacteria and organic matter in your pool will cause the chlorine to wear down quickly.

Once you notice the free chlorine ppm levels maintaining themselves for a longer amount of time, you can reduce how frequently you test your pool to two or three times per day.

Step 5: Clean Your Pool

As I mentioned earlier, floating debris will exhaust chlorine quicker than if it weren’t there. For this reason, you should regularly skim, vacuum, or brush your pool to aid the SLAM process.

I recommend cleaning your pool at least once per day. However, the more frequently you keep up with cleaning, the quicker you can get back to swimming in your pool.

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Signs That the SLAM Is Complete and Is Safe to Swim

SLAMing your pool is a time commitment, so you’ll no doubt be looking forward to the day when you can end it. To know that the SLAM worked, keep your eyes peeled for the following signs:

  1. No signs of cloudiness in the water.
  2. Your test kit shows that the combined chlorine level is 0.5 or under.
  3. The water held its chlorine level overnight without you needing to add more.

You’ll want to use an overnight free chlorine loss test (OCLT) to check the chlorine levels, as this test is sensitive to determining if bacteria, algae, and other pollutants are still using up the chlorine.

Because sunlight impacts chlorine levels, it’s best to perform the OCLT test after sunset and more than 30 minutes after adding chlorine. The following day, you’ll need to test the chlorine levels again. Provided that there isn’t more than a one ppm drop, you can end the SLAM and start enjoying your pool again.

And that’s about it for the SLAM: Shock, Level, and Maintain. Questions? Let me know.

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