How to Shock a Swimming Pool and Balance the pH

A swimming pool stays clear and hygienic when two things are right: the water is sanitised and the pH is in range. This guide covers how to shock a pool to restore clear water and how to keep the pH balanced so the chlorine can do its job.

What pool shocking means

Shocking a pool means adding a high dose of chlorine in one treatment to rapidly destroy bacteria, algae, chloramines and organic matter that normal day-to-day chlorination leaves behind. Hypo Pool Shock is a high-strength calcium hypochlorite granule for exactly this. It releases a large amount of available chlorine quickly, which is what clears cloudy or green water.

When to shock your pool

• When the water looks cloudy or green.
• After heavy rain.
• After a heavy swimmer load.
• On a routine schedule: about once a week during heavy use or after rain, and at least once a month during regular maintenance.

How to shock a pool

1. Test the water first and read the dosage chart on the pack for your pool volume.
2. Add the measured dose of Hypo Pool Shock with the pump running so it disperses evenly.
3. Wait 8 to 12 hours and keep the filter circulating.
4. Retest before anyone swims. Free chlorine should read between 1 and 3 ppm before the pool is safe to use.

Hypo Pool Shock works with concrete, fibreglass and vinyl liner pools, as well as saltwater systems and spas.

Why pH matters before and after you shock

The ideal pH range for a swimming pool is 7.2 to 7.6. When pH drifts too high, chlorine becomes less effective and scale forms on surfaces and equipment. When pH drops too low, the water turns corrosive and can irritate swimmers' eyes and skin. Balancing the pH is what lets your chlorine and shock treatment work as intended.

To lower high pH, use Pool Maxx pH Down. Add no more than half the recommended dose at a time to avoid a sudden drop, let the pool circulate for about 2 hours, then retest. To raise low pH, use Pool Maxx pH Up and retest after about 2 hours of circulation. Both work in pools, spas and saltwater systems.

If the water is still cloudy

Shocking kills algae and bacteria, but very fine particles can stay suspended and keep the water hazy. For that, a clarifier or flocculant helps the filter finish the job. Sparkle Maxx Pool Clarifier binds the fine particles together so the filter can trap them. Clear Maxx Pool Flocculant clumps particles so they settle to the floor for vacuuming.

A simple order of operations

1. Balance the pH to 7.2 to 7.6 first, so the chlorine works at full strength.
2. Shock the pool and wait 8 to 12 hours, then retest for 1 to 3 ppm free chlorine.
3. If the water is still hazy, add a clarifier or flocculant and let the filter clear it.