Comparing pool care choices
Chlorine shock or non-chlorine shock
Both are called shock. Only one of them kills algae. Choosing between them depends on what you are trying to fix.
Chlorine shock raises free chlorine well above normal to oxidise organic matter, break down chloramines and kill algae and bacteria. It is the treatment for green water, contamination incidents and heavy chloramine build-up. The drawback is that swimming must wait until chlorine falls back to a normal level.
Comparison guides set two pool care choices side by side and say when each suits.
Non-chlorine shock, usually potassium monopersulfate, oxidises organic matter and helps break down chloramines without raising chlorine. It suits routine oxidising after busy days when swimming needs to resume quickly. It does not kill algae or sanitise the water on its own, and it can affect some test readings of combined chlorine for a period after use.
The short version
Chlorine shock sanitises
It kills algae and bacteria as well as oxidising.
Non-chlorine shock oxidises only
It clears organic load and helps with chloramines but does not sanitise.
Swimming time differs
Non-chlorine shock usually allows swimming sooner.
When each is used
Algae or contamination
Chlorine shock is the appropriate treatment.
After a busy day
Non-chlorine shock can oxidise the extra load with less disruption.
Chloramine smell
Either can help; chlorine shock is more thorough when levels are high.
Before shocking
Identify the problem
Algae and contamination need chlorine shock.
Correct pH first
Both work better with balanced water.
Read the label
For dose, timing and swimming guidance.
Common questions
Can non-chlorine shock clear a green pool?
No. Green water needs chlorine to kill the algae.
Why does my combined chlorine reading look odd after non-chlorine shock?
Monopersulfate can interfere with some test methods for a while after dosing.
Can the two be used together?
They can be used at different times; follow label guidance and do not mix products.
Related pool care guides
- Repairing or replacing a pool pumpA related choice about how the pool is looked after.
- Treating a green pool or draining itA related choice about how the pool is looked after.
- Pool water that stings eyes and skinAnother water problem with a related cause.
- Metal stains in a poolAnother water problem with a related cause.
This guide sits under pool water treatment. Browse all pool care guides. We look after pools at homes and commercial properties across Dubai.
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