The SLAM Method stands for Shock Level And Maintain. It’s the process recommended by Trouble Free Pool to completely eliminate algae, bacteria, and organic contaminants from a swimming pool—not just temporarily “shock” it.

Unlike traditional pool shocking, where you dump in a bag of shock and hope for the best, SLAM keeps chlorine at a specific elevated level until the problem is completely gone.

When Should You Perform a SLAM?

A SLAM is recommended when:

• Water is green or cloudy
• Visible algae is present
• Combined Chlorine (CC) is above 0.5 ppm
• You fail an Overnight Chlorine Loss Test (OCLT)
• Pool water has a strong chlorine odor
• You’ve opened a neglected pool

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Step 1: Test Your Water

Before starting:

1. Adjust pH to 7.2–7.4
2. Test and record:
   • Free Chlorine (FC)
   • Combined Chlorine (CC)
   • Cyanuric Acid (CYA)

The SLAM chlorine level depends on your CYA level.

Example SLAM FC Levels

CYA	SLAM FC Level
20	10 ppm
30	12 ppm
40	16 ppm
50	20 ppm
60	24 ppm
70	28 ppm

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Step 2: Raise Free Chlorine to SLAM Level

Use liquid chlorine (sodium hypochlorite) whenever possible.

Avoid:

• Calcium Hypochlorite (adds calcium)
• Dichlor or Trichlor (adds stabilizer)

Add enough liquid chlorine to reach the required SLAM level based on your CYA.

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Step 3: Maintain the Chlorine Level

This is the most important part.

SLAM doesn’t mean adding chlorine once.

You must:

✅ Test FC frequently (2–4 times daily if possible)

✅ Add chlorine as needed to maintain the target FC level

✅ Keep the pump running 24/7

✅ Brush all pool surfaces daily

✅ Vacuum debris

✅ Empty skimmer and pump baskets

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Step 4: Clean the Filter Frequently

As algae dies, your filter works overtime.

Cartridge Filters

• Clean when pressure rises 20–25%

DE Filters

• Backwash when pressure rises 8–10 PSI above clean pressure

Common signs it’s time to backwash:

• Low flow
• Heater showing LO error
• Weak return jets
• Reduced waterfall or spa flow
• Rising filter pressure

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Step 5: Continue Until You Pass All 3 SLAM Criteria

Do not stop until ALL three conditions are met:

1. Crystal Clear Water

No cloudiness and no visible algae.

2. Combined Chlorine (CC) ≤ 0.5 ppm

3. Pass the Overnight Chlorine Loss Test (OCLT)

How to Perform OCLT

After sunset:

• Test and record FC
• Run pump overnight

Before sunrise:

• Test FC again

Pass if:

• FC loss is 1 ppm or less
• CC is 0.5 ppm or lower

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Example

Pool Size: 15,000 gallons

CYA: 40 ppm

Target SLAM FC: 16 ppm

Day 1:

• Raise FC to 16 ppm
• Brush pool
• Run pump continuously

Day 2:

• FC drops to 11 ppm
• Add chlorine back to 16 ppm
• Clean filter

Day 3:

• Water becomes clearer
• Continue maintaining 16 ppm

Day 4–5:

• Water is crystal clear
• OCLT passed
• CC = 0.2 ppm

SLAM Complete!

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Common Mistakes During a SLAM

❌ Adding shock only once

❌ Turning off the pump

❌ Not brushing walls and steps

❌ Letting chlorine drop below SLAM level

❌ Ignoring filter maintenance

❌ Stopping because the water “looks better”

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Gritz Pools Pro Tip

A successful SLAM is about maintaining chlorine, not simply adding a large amount once. The more consistently you keep chlorine at the proper SLAM level and maintain good circulation and filtration, the faster your pool will clear and return to sparkling condition.