Water, clarity and algae
A pool that turns cloudy after shocking
Shock is supposed to clear the water, yet sometimes it clouds it first. The cause is usually chemistry, or debris the filter has not caught yet.
Three causes account for most post-shock cloudiness. Calcium-based shock added to already hard water can push calcium out of solution. High pH at the time of dosing has the same effect. And when shock kills algae or breaks down contaminants, the debris stays in the water until the filter removes it, giving a grey or milky look.
Water guides explain what a reading or a symptom means and the order in which to correct it.
The fix depends on which one it is. Testing pH, alkalinity and hardness tells you whether chemistry is to blame. If it is debris, continuous filtration and cleaning the filter as it loads usually clears the water, with a clarifier helping the finest particles reach the filter.
The short version
Calcium shock in hard water
Adds calcium to water that is already near its limit.
High pH when dosing
Encourages calcium to precipitate and reduces how well the shock works.
Dead algae and debris
Stay suspended until the filter catches them.
Clearing the cloudiness
Balancing the water
pH and alkalinity are brought into range so calcium stays dissolved.
Filtering continuously
The pump runs continuously and the filter is cleaned or backwashed as pressure rises.
Clarifying if needed
A clarifier groups fine particles so the filter can trap them.
Next time you shock
Match the shock to your water
In hard water, a non-calcium shock such as liquid chlorine avoids adding hardness.
Correct pH before dosing
The shock works better and clouds less.
Plan a filter clean afterwards
It removes what the shock has killed.
Common questions
Will the cloudiness clear by itself?
Often, with filtration, but correcting the chemistry speeds it up and stops it recurring.
Is cloudy water safe to swim in?
Avoid swimming until the water is clear and chlorine is back in the normal range.
Should I shock again?
Only if free chlorine has dropped. More shock in hard, high-pH water can deepen the cloudiness.
Related pool care guides
- Partially draining and refilling a poolAnother water problem with a related cause.
- Removing scale from pool tilesAnother water problem with a related cause.
- Dealing with a contamination incident in a private poolPool care for a related situation.
- Liquid chlorine or chlorine tabletsA related choice about how the pool is looked after.
This guide sits under pool water treatment. Browse all pool care guides. We look after pools at homes and commercial properties across Dubai.
Ask about your pool
A clear photograph and your latest test reading are usually enough for a useful first answer.
Phone
+971 56 181 0106Talk through what the pool is doing and book a time for us to see it.
WhatsApp
Send a messageThe easiest way to send photographs of the pool and plant room.
Next step
Pool still cloudy after shocking?
Send your test results and tell us what shock you used. We will help clear the water and adjust the routine.