Domakihub How to Shock a Pool the Right Way
A simple, safe routine to clear cloudy or green water and keep your pool sanitary.
Reviewed by Domakihub pool pros · 2026-06-23 · 4 min read
Shocking a pool means adding a strong dose of chlorine to kill bacteria, clear algae, and burn off the contaminants that everyday chlorine cannot handle. The video above shows the process in action, and this guide breaks it into clear, ordered steps you can follow safely. Whether you manage a family home, a holiday rental, or a hotel pool here in Greece, doing this correctly keeps the water sanitary and swim-ready through the long summer season.
Why and when to shock your pool
Over time, sweat, sunscreen, rainwater, and organic debris combine with chlorine to form chloramines, the compounds responsible for that harsh chlorine smell and irritated eyes. A shock treatment delivers enough free chlorine to break those compounds apart, kill bacteria, and reset the water.
For most pools, a routine shock once a week is sensible during peak summer. Shock more often after heavy use, a big pool party, a rainstorm, or whenever the water turns cloudy or green. High-traffic rental and hotel pools in Greece's heat often benefit from a regular weekly schedule plus an extra dose after busy weekends.
Types of pool shock
The two most common options are cal-hypo (calcium hypochlorite), a fast-acting granular shock ideal for clearing green water, and dichlor, a stabilised granular shock that is gentler on most surfaces. Liquid chlorine is another option that needs no pre-dissolving. Always read the product label, because dosing and handling differ by type.
Cal-hypo is powerful and economical but raises calcium hardness over time, while dichlor adds cyanuric acid (stabiliser) that can build up with repeated use. Choose based on your pool surface, current water chemistry, and how quickly you need results.
How to shock your pool step by step
- 1
Test the water first
Use a test kit or strips to check your current chlorine, pH, and stabiliser levels. Aim to bring pH into the 7.2 to 7.6 range before shocking, because chlorine works far more effectively in balanced water. Testing also tells you how badly the water is contaminated so you can dose correctly.
- 2
Calculate the correct dose
Read the product label and match the amount to your pool's volume in cubic metres or litres. A normal maintenance shock is one dose, but clearing green or cloudy water often calls for a double or triple dose. Never guess; under-dosing wastes product and over-dosing can damage surfaces.
- 3
Pre-dissolve granular shock
Fill a clean plastic bucket with pool water, then slowly add the granular shock and stir until dissolved, one dose at a time. Pre-dissolving prevents undissolved granules from sinking and bleaching or staining the pool floor. Skip this step only if you are using liquid chlorine, which can be poured directly.
- 4
Pour it in with the pump running
With the filtration pump on, slowly pour the dissolved shock around the perimeter of the deep end so it circulates evenly. Run the pump for several hours, ideally overnight, to distribute the chlorine fully and let it do its work throughout the water.
- 5
Wait, retest, then swim
Do not swim until the free chlorine level drops back to a safe 1 to 3 ppm, which usually takes a number of hours or until the next day. Retest before anyone enters the water. For a green pool, you may need to brush, let the filter clear the dead algae, and repeat the shock until the water turns clear.
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FAQ
- How long after shocking a pool can you swim?
- Wait until the free chlorine level falls back to a safe 1 to 3 ppm, which typically takes a few hours to overnight depending on the dose. Always retest with a kit before swimming rather than guessing, as entering water with very high chlorine can irritate skin and eyes.
- Should I shock my pool during the day or at night?
- Shock in the evening or at night. Sunlight rapidly breaks down unstabilised chlorine, so shocking after sunset lets the chlorine work through the night for maximum effect before the next day's sun.
- Can I shock a pool too much?
- Yes. Over-shocking wastes product, can bleach or damage some liners and surfaces, and leaves the water unsafe to swim in for longer. Follow the label dosing for your pool's volume, and for stubborn green water increase the dose gradually rather than dumping in far more than recommended.