How To SLAM A Pool In 5 Steps (A Different Kind Of Shocking)



No one likes dirty water, and keeping it clean is vital to keeping swimmers safe.

Sanitizers like chlorine or bromine are used for this exact reason, and yet, pool water can still go sideways.

At this point, many people will shock their pool to restore its cleanliness, but “SLAMing” takes pool sanitization to a whole new level. 

Let’s go over how to SLAM a pool the right way.

What Does It Mean To SLAM Your Pool?

SLAM is a pool water sanitization process that stands for Shock, Level, and Maintain — originating from the website, Trouble Free Pool.

The goal of SLAMing is to add so much chlorine to the pool that it completely oxidizes all pollutants in the water – algae, bacteria, viruses, and any other organic contaminants. The long term nature of SLAMing breaks down the pollutants to a molecular level until they are rendered harmless.

This is reserved for when your pool is green from an algae bloom, or when the combined chlorine level of the pool is higher than 0.5 ppm. For reference, the ideal level of combined chlorine is under this number.

The process entails adding chlorine to a swimming pool until it reaches a high free chlorine shock level. You then maintain this level until it gets the pool water crystal clear by eradicating all pollutants, including algae

It’s also important to note that any pool can be SLAMed, so you aren’t limited if you have a concrete, fiberglass, or vinyl liner pool.

SLAMing Vs Traditional Shocking

While they are similar, SLAMing is not the same as shocking your pool.

Pool shocking is done when there’s a high level of combined chlorine in the water, and low levels of free chlorine available. 

Shocking takes place overnight by dosing the pool with a high level of free chlorine. This reduces the combined chlorine and restores the free chlorine levels in the pool. In very dirty pools, you may need to shock a few times to fully clean the water.

Pool SLAMing differs because it’s a long-term process (it can last from a few days to a few weeks) of continually dosing the pool with large amounts of free chlorine, reducing the water’s combined chlorine levels while raising free chlorine.

Finally, unlike traditional shocking, SLAMing requires regular testing of your pool water, ensuring the free chlorine is topped up (maintained) so it doesn’t drop below shock level. This must be done for the entire duration of the SLAM.

Before You Start The SLAM

Before slamming, you’ll need to do some prep work. 

The first thing you’ll need to get is a boatload of liquid chlorine. Remember, this is a multi-day process. Free chlorine levels need to be high the entire time, so make sure you have enough chlorine on hand.

Next, ensure the pool pump can be left running for the full duration of the SLAM. Check that you pump is in good working order, and running it for an indefinite amount of time won’t disturb your neighbors. 

You’ll also need to pre-clean the pool by skimming any leaves or debris out of it, and check your skimmer baskets and filter to make sure they’re clean and ready for the process.

Finally, test the pool water using a digital testing kit (highly accurate) or testing strips to get levels for your pool’s pH, cyanuric acid (CYA), and free chlorine. An FAS-DPD chlorine test is recommended to give you the most accurate free chlorine level. 

How To SLAM Your Pool (5 Steps)

SLAMing the pool isn’t too difficult, but it does require you to follow the right steps and monitor the situation while the process unfolds.

1. Adjust Your pH Level

The first thing you need to do is bring down the pH level.

The ideal pH level for a clean pool sits between 7.4 and 7.6, but when you SLAM you’ll have to bring down the pH level to 7.2.

This is done because over the course of the SLAM, pH testing becomes unreliable due to the massive chlorine levels in the water. Test and adjust your pH level to start.

2. Adjust Your Cyanuric Acid Level

Testing and adjusting your cyanuric acid (also referred to as pool stabilizer) is next. This test will determine the free chlorine shock level that’s needed for the pool. 

The ideal range for cyanuric acid in your pool is between 30 and 50 ppm, and this is no different when performing a SLAM.

The pool must have a minimum cyanuric acid level of 30, and should not be over 90. If it is, dilute the pool water to bring it into the proper range before starting the SLAM. 

3. Add Chlorine To Reach Shock Level

So how much chlorine do you add? 

This can be determined using Trouble Free Pool’s chlorine/CYA chart, which tells you the exact level you’ll need. As the chart shows, a pool with a lower level of CYA at 30 ppm needs to be SLAMed with a free chlorine level of 12 ppm consistently

(Considering the ideal free chlorine level is normally kept between 2 and 4 ppm, you can imagine how much chlorine is needed to spike it to 12!)

Use the app, get the proper dosage for your pool, then pour the chlorine directly in line with the return jets so they circulate it quickly.

4. Continue To Maintain Shock Level

The chlorine you add to the pool will eventually dissipate.

You’ll need to frequently test the water (a minimum of twice per day) and top up the chlorine after each test, maintaining its high shock level for the duration of the SLAM. 

Also of note, algae and other pollutants will eat up chlorine quickly – especially at the beginning, so testing the water every few hours is recommended.

5. Keep The Pool Clean (While You Wait)

While this process is ongoing, keeping the pool free of any additional pollutants will help speed things up. You can do this by brushing and vacuuming the pool daily, and skimming it to keep floating debris out.

When Is The SLAM Complete?

Once the SLAM begins, you cannot stop the process until all 3 of the following conditions have been met:

  • The water is clear
  • The water passes the overnight free chlorine loss test (OCLT)
  • The combined chlorine level is 0.5 or less

The OCLT is a test that determines if there’s still contaminants in the pool such as algae that are continuing to use free chlorine. Chlorine is also used up by sunlight, so performing this test when there is no sun is imperative.

Using the FAS-DPD test, record the free chlorine level after sunset (and at least 30 mins after your last chemical addition). If it’s over 3 ppm, stop adding chlorine to the pool, and then retest the water in the morning before sunrise. 

If the free chlorine level stayed the same, or dropped by 1 ppm, the water is clean. If the free chlorine level dropped by more than 1 ppm, there’s still contaminants in the water, and SLAMing should resume.

Your Pool, Reborn.

Don’t settle for swimming in a pool that isn’t performing at it’s best. 

By using the SLAM method, there’s a way to have crystal clear water all the time, by restoring it to the cleanest state it can possibly be in. 

Categories: Pool Care, Pool Chemistry