Home SLAM Method Calculator
SLAM Calculator — CYA-Based Green Pool Treatment
Calculate the Trouble Free Pool-style SLAM FC target from measured CYA, then estimate the first 10% liquid-chlorine dose from your current FC. SLAM is a community operating method, not a CDC regulatory standard.
💡 TFP SLAM method used on this page
SLAM target FC = CYA × 40%
Example: CYA 40 ppm → TFP SLAM target 16 ppm FC.
The “Maintain” part matters: test and redose to the measured target until the method's completion criteria are met.
Important: the TFP minimum FC shown on this page is an operating floor within that method — not a universal swimmer-safety threshold.
💡 Before treatment, measure pH, CYA and FC with suitable tests. At elevated FC, some pH/color tests can become less reliable; follow your test-kit instructions and the TFP method you are using.
Useful SLAM supplies:
- High-range chlorine test kit — needed to measure elevated FC reliably
- Liquid chlorine — the calculator uses a 10% sodium-hypochlorite basis
- Pool brush — brushing and filtration are part of the method
Example calculation
A 20,000 gallon pool with a CYA of 40 ppm and current FC of 2 ppm needs to be SLAMed:
| Input | Value |
|---|---|
| Pool volume | 20,000 gallons |
| CYA level | 40 ppm |
| Current FC | 2 ppm |
| SLAM target FC | 16 ppm (40 ÷ 10 × 4) |
| FC increase needed | 14 ppm |
| Liquid chlorine to add | ~2.8 gallons (first dose) |
| Recommended to buy | 10 gallons (3–4 days supply) |
Formula: (Pool gallons × FC increase needed) ÷ 100,000 = gallons of 10% liquid chlorine
CYA to TFP SLAM target FC chart
| CYA | TFP SLAM FC (40%) | TFP manual-pool operating minimum (7.5%) | Planning note |
|---|---|---|---|
| 20 ppm | 8 ppm | 1.5 ppm | Low CYA; confirm this is intentional. |
| 30 ppm | 12 ppm | 2.3 ppm | Common lower outdoor range. |
| 40 ppm | 16 ppm | 3.0 ppm | Common reference row. |
| 50 ppm | 20 ppm | 3.8 ppm | Higher chlorine treatment target. |
| 60 ppm | 24 ppm | 4.5 ppm | Higher chlorine demand. |
| 70 ppm | 28 ppm | 5.3 ppm | Consider whether dilution is practical. |
| 80 ppm | 32 ppm | 6.0 ppm | Large chlorine demand. |
| 90 ppm | 36 ppm | 6.8 ppm | Consider dilution; not a universal safety cutoff. |
| 100 ppm | 40 ppm | 7.5 ppm | Very large treatment demand. |
Rows are arithmetic representations of the TFP-style 40% SLAM relationship and 7.5% manual-pool operating minimum. Salt-generator operating targets differ on the site's CYA/FC page.
Step-by-step SLAM process
- Confirm the method and test accurately. Measure CYA and FC with a test method capable of the elevated FC range.
- Calculate the TFP SLAM target from CYA. This page uses 40% of measured CYA.
- Add a measured liquid-chlorine dose to reach the target. Product strength degrades with age/storage, so retest rather than assuming one addition was exact.
- Maintain the target. Test frequently and redose as FC is consumed.
- Brush, circulate and filter. Clean/backwash the filter as pressure and the equipment instructions indicate.
- Continue until the TFP completion criteria are met: water is clear, combined chlorine is 0.5 ppm or less, and the Overnight Chlorine Loss Test loses 1.0 ppm FC or less.
If CYA is very high, the 40% relationship creates a very high treatment target. Partial dilution may be more practical, but this page does not declare one CYA number a universal “unsafe to SLAM” cutoff.
Before, during and after a SLAM treatment
Before you start
Confirm pool volume, measure CYA and FC, remove debris, verify that circulation/filtration is operating, and use a chlorine test method that can read the elevated treatment range. If CYA is unmeasurable, do not extrapolate the 40% relationship from zero; establish a measured CYA value appropriate to the method first.
During the treatment
The first calculated liquid-chlorine amount only gets the water from the measured current FC to the treatment target. Ongoing chlorine demand depends on the algae/contaminant load, sunlight, circulation and how often FC is tested and restored. Brush pool surfaces, keep circulation/filtration operating as appropriate, and clean/backwash the filter according to its pressure and manufacturer instructions.
After the completion criteria are met
Stop maintaining the elevated treatment target and return to the normal FC target used by your chosen operating method. Recheck the broader water balance, clean the filter as needed, and investigate circulation, debris or recurring chemistry issues if algae returns quickly.
Liquid chlorine vs. granular products
This calculator uses liquid chlorine because its sodium-hypochlorite concentration can be converted directly into an FC increase without also adding calcium or CYA. Granular products vary by active ingredient and strength; if you use one, calculate from that exact product label and account for its side effects instead of substituting the liquid-chlorine gallon result.
Liquid chlorine dose chart by pool size
How much 10% liquid chlorine (sodium hypochlorite) to raise free chlorine by common amounts. Use this as a cross-reference alongside the calculator above.
| Pool size | +5 ppm FC | +10 ppm FC | +15 ppm FC | +20 ppm FC |
|---|---|---|---|---|
| 10,000 gal | 0.5 gal | 1.0 gal | 1.5 gal | 2.0 gal |
| 15,000 gal | 0.75 gal | 1.5 gal | 2.25 gal | 3.0 gal |
| 20,000 gal | 1.0 gal | 2.0 gal | 3.0 gal | 4.0 gal |
| 25,000 gal | 1.25 gal | 2.5 gal | 3.75 gal | 5.0 gal |
| 30,000 gal | 1.5 gal | 3.0 gal | 4.5 gal | 6.0 gal |
Based on 10% sodium hypochlorite. If using 12.5% liquid chlorine, multiply all amounts by 0.8. Use our chlorine calculator for other chlorine types.
SLAM method vs. a one-time shock dose
A one-time shock dose is a single addition to a target selected for that treatment. SLAM is different: within the Trouble Free Pool method, FC is raised to a CYA-based target and maintained there until the method's completion criteria are met.
For a one-time treatment target that you already know, use the Shock Calculator. For active SLAM, use this page.
Why this calculator uses liquid chlorine for the dose estimate
The dose calculation uses 10% sodium hypochlorite because its concentration can be translated directly into an FC increase without adding calcium hardness or CYA. Actual strength can fall during storage, so the calculator still requires retesting and maintenance.
SLAM method calculator FAQs
What does SLAM mean in pool care?
SLAM stands for Shock Level And Maintain. On this site it refers specifically to the Trouble Free Pool-style method of raising FC to a CYA-based target and maintaining that target until the method's completion criteria are met.
How does this calculator choose the SLAM FC target?
It uses the TFP-style relationship SLAM FC = 40% of measured CYA. For example, CYA 40 ppm produces a 16 ppm treatment target.
Is the TFP minimum FC a safe-swimming limit?
No. It is an operating floor within that pool-care method, not a universal swimmer-safety threshold. Follow product/local guidance and never swim when water is green, cloudy or visibility is poor.
Do I have to drain if CYA is above 90 ppm?
No universal safety cutoff is asserted here. Higher CYA creates a proportionally higher SLAM target and larger chlorine demand, so partial dilution may be more practical. Use the Pool Dilution Calculator and consider your pool's drain-safety constraints.
How do I know when SLAM is complete?
The TFP-style completion criteria used here are clear water, combined chlorine of 0.5 ppm or less, and an Overnight Chlorine Loss Test of 1.0 ppm FC or less.
Why do I need a high-range chlorine test?
SLAM targets can exceed the useful range of common color tests. CDC notes that some DPD tests can bleach out above about 10 ppm and appear falsely low or zero, so follow your test-kit instructions and use a method suited to the concentration.
Should I turn off a salt chlorine generator during SLAM?
This calculator does not assume one universal shutoff or damage threshold for every generator. Manual liquid-chlorine dosing is easier to measure during treatment, but follow the salt-generator manufacturer's instructions for operation at elevated FC.
Can I use granular shock instead of liquid chlorine for SLAM?
Granular chlorine products vary by active ingredient and concentration and can also add calcium or CYA. This calculator uses liquid chlorine because its sodium-hypochlorite strength can be converted directly into an FC increase. If you use a granular product, calculate from that exact label and account for its side effects.
What if my CYA is zero or unmeasurable?
Do not apply the 40% relationship to a zero or guessed CYA value. The TFP-style method is CYA-based, so establish a measured CYA value appropriate to the method before using this calculator.
How much liquid chlorine will the entire SLAM process use?
The calculator can estimate the first dose from current FC to the treatment target, but it cannot predict the total treatment amount. Ongoing demand depends on algae and contaminant load, sunlight, circulation, filtration and how often FC is tested and restored.
How long does a SLAM treatment take?
There is no defensible fixed number of hours or days. Continue the method until its completion criteria are met: clear water, combined chlorine at or below 0.5 ppm, and an Overnight Chlorine Loss Test of 1.0 ppm FC or less.
What should I do after SLAM is complete?
Stop maintaining the elevated treatment target, return to the normal FC target used by your operating method, and recheck broader water balance. Clean or service the filter as needed and investigate circulation or recurring chemistry issues if algae returns.