By The Zagosa Team. Published .
Reviewed or updated .
Shock is brilliant at clearing cloudiness caused by oxidisable organic matter. If the haze hangs around after a strong dose and good circulation, the cause is one of four other things: high pH or alkalinity, calcium scaling, suspended fines that call for a clarifier, or a filter on its way out.
Start by ruling out chemistry
Test pH and alkalinity. If pH is above 8.0 or alkalinity above 180 ppm, you have classic high-pH cloudiness. Calcium and metals drop out of solution and show up as a milky haze.
The fix is a careful dose of pH decreaser, a retest after an hour, and a repeat as needed. The haze usually clears within four to six hours of pH returning to band.
Then check the filter
Pull the filter out and look it over. Compressed pleats, discolouration, or a sticky film point to a failing filter rather than the chemistry.
A proper overnight soak in a dedicated filter cleaner often revives a tired filter. Anything older than 18 months is better simply replaced.
A fresh or cleaned filter plus a clarifier (which clumps tiny particles together so the filter can trap them) clears most stubborn haze within 24 hours.
Then look at total dissolved solids
If you are past the 12-week refill mark and the water has been through several heavy sessions, TDS may be high enough that the water simply cannot hold any more dissolved load.
There is no chemical fix for high TDS. A 30 to 50% partial drain and refill is the answer.
While you are there, run a pipe purge product the night before draining. Biofilm in the lines is often the unseen culprit behind lingering cloudiness.
Common questions
Should I keep shocking until it clears?
No. If the first heavy shock has not cleared it within 12 hours, more shock will not help. Diagnose the cause first.
Can a clarifier and a shock go in the same day?
Yes. Shock first, run the jets 30 minutes, then add clarifier. The shock oxidises the organics so the clarifier can clump the inorganic fines without competition.