FILTRATION HYDRODYNAMICS โ€ข 5 MIN READ

How to Clear a Cloudy Pool in 24 Hours (Clarifier vs Flocculant Protocol)

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Written by David Vance, CPOCertified Pool & Spa Operator #48291 โ€ข Certified Field Protocol
Crystal clear swimming pool water with testing probe
The 10-Micron Filtration Barrier: Suspended dead algae and microscopic dust are smaller than 5 microns. Standard sand filters only capture down to 20 microns; without electrostatic coagulants or continuous turnover, dead particles recirculate indefinitely.

Nothing ruins a summer weekend faster than walking out to a dull, milky-white swimming pool where you cannot even see the main drain screws on the deep-end floor.

Cloudy water stems from one of three distinct root causes: early-stage microscopic algae bloom, calcium carbonate precipitation from high pH, or insufficient filter turnover. Dumping random 'miracle clarifiers' without testing first makes cloudy water twice as bad.

0MS CLOUDINESS TRIAGE

Cloudy Water Chemical Decision Matrix

Answer two visual checkpoints to determine whether you need high-dose chlorine shock, polymeric clarifier, or aluminum sulfate flocculant.

PRESCRIBED PROTOCOL
Liquid Chlorine SLAM
Eradicate dead algae spores
CHEMICAL AGENT
12.5% Sodium Hypochlorite
Zero added CYA or Calcium
FILTER ACTION
24 Hr Continuous
Rinse cartridge every 8 hrs
CLEAR WATER ETA
18 - 24 Hours
With active circulation
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01Run an Overnight Chlorine Loss Test (OCLT)

Before adding clarifiers, test your Free Chlorine at sunset, then test again at sunrise before direct sunlight hits the water. If you lose more than 1.0 ppm FC overnight, live organic algae is actively dividing in your water. No clarifier will fix it; you must elevate chlorine to shock level (SLAM) until overnight loss is zero.

02When to Use Polymeric Clarifier vs Flocculant

Clarifier is mild and works with all filter types (including cartridges) over 48 hours by binding small particles into filter-sized clumps. Pool Flocculant (Aluminum Sulfate) drops all dirt to the floor like a heavy blanket in 8 hours, but requires a multiport valve to vacuum directly to WASTE. Never use flocculant in a cartridge filter or you will cement the pleats permanently.

03Add 1 Cup of D.E. Powder to Sand Filters

If you have a sand filter, slurry 1 cup of Diatomaceous Earth (D.E.) powder with water and pour it into the skimmer. The D.E. coats the top layer of sand, instantly increasing filtration efficiency down to 3 microns and stripping dull haze out of your water in under 12 hours.

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Don't guess dosages when your water is dull or cloudy. Use our 0ms dynamic water balance engine to calculate exact chemical additions for your entire pool volume and prevent algae blooms.

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