Pool Shock vs Regular Chlorine: When to Use Which

Routine chlorination

Use trichlor tabs in a floater or feeder for slow, steady chlorine release. Tabs also add CYA, which is helpful in the first month of pool season and a problem later.

Liquid chlorine works for daily top-up. Easy to dose, no impact on pH (slightly raises). No CYA contribution.

When to shock

After a heavy rain or pool party (high organic load).

When chlorine has dropped to zero and the water is cloudy.

Before closing the pool in fall.

After opening in spring before swimming.

Any time you see early algae.

Choosing the right shock

Cal-Hypo (calcium hypochlorite): cheapest per pound, raises calcium hardness over time. Best for new pools and pools with soft water.

Dichlor: adds CYA. Use sparingly unless you need to raise CYA along with chlorine.

Non-chlorine shock (potassium peroxymonosulfate): does not add chlorine. Use to oxidize organics without spiking chlorine levels. Safer when bathers want to swim within 4 hours.

How to add shock safely

Always add to water, never water to shock. Pre-dissolve granular shock in a bucket if your pool surface is vinyl or you have a sun-bleached floor.

Add at dusk so sunlight does not burn off the chlorine before it works.

Brush after to disrupt any biofilm and let the shock contact every surface.