Shock treatment: when, how, and the traps to avoid
- A shock is for hitting hard once: algae, chloramines, turning water, after a storm or heavy bathing.
- The order is non-negotiable: clean → test → correct the pH → shock → filter continuously → re-test.
- Trap number one: underdosing (the internet's generic doses), which pushes the problem back without killing it.
- Shock ≠ swimming: the app tracks the level and shows you when the water is swimmable again.
The shock treatment is the pool’s heavy artillery: a massive, one-off input of sanitiser to take back control when the water has tipped over — algae, chloramines, water turning after a storm or a busy weekend. Run well, it settles in 24-72 hours situations that drag on for weeks under half-measures. The order of operations is non-negotiable: clean, test, correct the pH, shock, filter continuously, re-test. And the crux is the dosing: a shock is calculated on your volume, your product and your current level — not on a forum’s generic dose. That’s precisely what the CliniPool app does.
When a shock is justified (and when it isn’t)
A shock answers an event: green or turning water, a strong chlorine smell (chloramines), after a debris-laden storm, after a very busy party, at the spring opening, or on recommendation after an incident (vomit, faeces — see the emergencies). Conversely, a balanced pool doesn’t need routine “maintenance” shocks: that’s a sales myth that wears out the water, the wallet — and the stabiliser, if the product contains any.
Why so many shocks fail
Underdosing, first. Most failed shocks are timid shocks: enough chlorine to make the algae go pale, not enough to kill them — and in the case of chloramines, underdosing creates new ones instead of destroying them. The “universal” doses found online ignore your starting point: that’s mathematically a recipe for underdosing.
The forgotten pH, second. A shock into water at pH 7.8+ works at a fraction of its strength. Five minutes of correction before the shock multiplies its effectiveness.
The saturated stabiliser, last. If your previous shocks (with stabilised chlorine) achieved nothing, measure the stabiliser before trying again: too high, it neutralises everything, and every stabilised shock makes the problem worse.
The sequence, in practice
Follow the six steps in the guide above (they’re also in the app’s guided plan, with timers): cleaning, test, pH, calculated shock, continuous filtration, re-test. Two absolute safety rules: always dissolve/pour the product into the water (never the other way round), and never mix different chlorine products together, even “to finish off a bucket” — some mixtures react violently, dry or in solution.
Swimming during and after
During a shock, the sanitiser is deliberately far above the swimming ranges: you don’t swim, full stop. The real question is “when can we dive back in?” — and the right answer isn’t a universal number of hours but a measured level. The app tracks the chlorine’s comedown after your shock and flips the swim indicator to green when YOUR water gets there; the swimming-wait guide (“Also worth reading”) explains the logic.
Frequently asked questions
Shock chlorine vs normal chlorine — what's the difference?
A "shock" is a massive, fast input (quick-dissolving powder or granules, often unstabilised), designed to climb very high very quickly. Everyday maintenance aims for stability; a shock aims for the breakpoint.
How long after a shock can you swim?
When the free chlorine has come back down into the swimming range — anywhere from a few hours to a day or two depending on dose, sun and volume. The app tracks the comedown and tells you in real time, rather than a vague rule.
Should you shock regularly "for maintenance"?
No. A balanced, regularly tested pool almost never needs a routine preventive shock. A shock is justified by an event: algae, chloramines, a storm, heavy bathing, the spring opening.
Why didn't my shock work?
Three causes, in order of likelihood: insufficient dose (generic instead of calculated), pH too high at the time of the shock, stabiliser too high neutralising the chlorine. All three can be checked with a test.