In this guide: The four causes · Step-by-step fix · Clarifier vs flocculant · Calculators
Cloudy water is the pool telling you that something — chemistry, filtration, or circulation — has fallen behind. The particles making it hazy are usually far too small for the filter to catch on their own, so the fix is to get the chemistry right, run the filter hard, and if needed, clump the fine particles together so they can be removed.
Chemistry out of balance — low free chlorine (letting algae and bacteria bloom) or high pH (which makes chlorine sluggish and can cloud the water on its own). Poor filtration — a dirty or undersized filter, or a filter that simply isn't running enough hours. Poor circulation — dead spots where water barely moves. High load — a rainstorm, a crowd of swimmers, sunscreen, or fine dust that overwhelms the system.
Work in this order and give each step time before judging it:
1. Test and balance. Bring pH into the 7.2–7.6 range first — chlorine barely works above 7.8. Then confirm free chlorine is in range.
2. Shock the pool. A full breakpoint dose oxidizes the organic haze. Dose to your volume (see the shock guide) and run the pump.
3. Run the filter continuously. Until the water clears, run 24/7. Backwash sand/DE or rinse the cartridge when pressure rises 8–10 psi.
4. Help the filter. If it's still hazy after a day, add a clarifier or flocculant (below).
5. Brush and vacuum anything that settles to the floor.
A clarifier gently gathers fine particles into larger clumps the filter can then trap. It's slow (a day or two), low-effort, and you keep filtering normally — the right choice for mild haze. A flocculant (floc) forces everything to sink to the floor as a dense layer, which you then vacuum to waste (bypassing the filter). It clears severe cloudiness in hours but you lose some water and it's more work. Dose either product to your actual gallons — this is where knowing your volume and filter type pays off.
These calculators turn the steps above into your exact numbers:
This guide is built on published health codes, national standards, and government energy guidance. For the exact equations behind the linked calculators, see our formula reference.
This guide is general information, not a substitute for your local health code or a licensed professional. Always follow the dosing instructions on your chemical labels and confirm readings with a test kit.