Master pool care cheat sheet →
⚡Reference cheat sheet
Pool Shock Cheat Sheet
When to shock, how high to go for your CYA, and which product to use.
Updated · Reviewed by the Skimmer editorial team
When to shock
- Combined chlorine over 0.5 ppm (the chlorine smell)
- After a storm, a party or heavy swimming
- When the water starts to haze or turn green
- When you open the pool
How high to shock by CYA
| CYA (ppm) | Routine / after a party | Green / SLAM |
|---|---|---|
| 30 | 10 ppm | 12 ppm |
| 40 | 10 ppm | 16 ppm |
| 50 | 12.5 ppm | 20 ppm |
| 60 | 15 ppm | 24 ppm |
| 70 | 17.5 ppm | 28 ppm |
| 80 | 20 ppm | 32 ppm |
Get the exact dose for your pool and product with the pool chlorine calculator.
Which shock
| Product | Best for | Side effect |
|---|---|---|
| Liquid chlorine | Everything, especially SLAM | None to speak of |
| Cal-hypo | Occasional shock in soft water | Adds calcium |
| Dichlor | Spas, small doses | Adds CYA fast |
| Non-chlorine (MPS) | Oxidizing after a party | Does not kill algae |
Note: Shock at dusk with the pump running, so the sun does not burn it off. Swim once FC is back under about 10 ppm.
Free from skimmerpoolcare.com. Log today's test in Skimmer: Pool Care Log on the App Store.
General reference for residential pools. Product labels and local guidance override any figure here. See our methodology and editorial policy. Skimmer · skimmer pool care.
Frequently asked
Shock cheat sheet: questions
How often should I shock my pool?
Only when you need to: combined chlorine over 0.5 ppm, after heavy use or a storm, or when the water starts to turn. Pools held at the right FC for their CYA rarely need it.
Is superchlorination the same as shocking?
Close. Both mean raising chlorine well above normal. Breakpoint shocking aims to clear combined chlorine; SLAM holds a high level until algae is gone.