One Cloudy Pool, Three Tints: Green Vs White Vs Brown Triage Decision Tree

Why this matters

"Cloudy" is a symptom, not a diagnosis, and the tint of the cloud is the fastest free clue you have on a drive-by. Green-tinted cloud, milky-white cloud, and brown or tan cloud have three different root causes that demand three different first moves: kill algae, fix balance and filtration, or address metals and sediment. Reaching for shock on every cloudy pool wastes chemical on the white and brown cases and can drive metals out of solution, making a brown pool worse. Reading the tint first routes you to the right test set on the first visit.

Cloudiness itself is just suspended particulate scattering light, but what the particles are tells you the cause, and the dominant color is your free read before any reagent comes out of the kit. The discipline is to name the tint, form a hypothesis, and let the panel confirm or reject it, rather than defaulting to the same shock-and-clarifier routine on every cloudy call regardless of color.

Symptom presentation

• Green tint, cloudy: water has a green cast, walls may feel slick, FC is often low. Algae bloom in progress.
• White or milky tint: water is uniformly hazy white-gray, you cannot see the main drain, but there is no color. Usually fine particulate from balance, filtration, or a chemical reaction.
• Brown or tan tint, cloudy: water carries a brown, rust, or tea-colored haze. Metals oxidizing, stirred sediment, or organic tannins.

Quick checks

• Full panel: FC, CC, pH, TA, CH, CYA. The chemistry sorts most of these. A low FC with elevated CC leans green/algae; a positive LSI with high CH and pH leans white/calcium; a positive metal test leans brown.
• Filter status: read filter pressure and time since last clean or backwash, and note the filter type. A clogged, channeling, or undersized filter underlies many white-haze cases, and a DE filter run with no fresh powder passes fines straight back to the pool.
• Visual and tactile: slick walls suggest algae; gritty suspended particles that you can almost feel suggest a filtration miss; staining on the plaster underneath the haze suggests metals.
• History: recent rain (drops FC and adds phosphates and debris), a new well fill (metals), a fresh shock (can cloud from precipitation or drive metals out), or a high-bather-load weekend (organic load) each steer the diagnosis. Ask before you test so the timeline frames the panel.

Isolation tree

• Step 1 - Read the tint and branch.
• Green branch. Confirm low FC and possibly elevated CC. Algae confirmed by slick surfaces and green cast. Test FC relative to CYA; an under-chlorinated, over-stabilized pool is the classic setup for a bloom. Move to remediation for algae.
• White branch. No color, milky haze. Sub-isolate:
  • High pH or high CH with positive LSI: calcium clouding (carbonate precipitation), often after a pH spike or a calcium-based shock. Correct balance.
  • Recent chemical reaction (shock, flocculant, or a clarifier overdose) leaving fine particulate the filter cannot catch.
  • Filtration failure: dirty, channeling, or undersized media; a DE grid with no powder; a cartridge past its life. Address the filter.
  • High bather load and TDS with fine organic load: oxidize and filter.
• Brown branch. Sub-isolate:
  • Metal test positive (iron, manganese) after a well fill or after pH was driven high: oxidized metals clouding the water. Sequester and filter, do not shock blindly.
  • Sediment stirred from the floor (post-storm, after vacuuming to waste, or a cleaner kicked it up): mechanical, clears with circulation and filtration.
  • Organic tannins from runoff, leaves, or nearby vegetation: oxidize and filter.

Confirming diagnosis

• Green/algae: low FC, slick walls, green cast that intensifies in warm still water; FC well below the CYA-appropriate level.
• White: no color, haze persists with adequate FC; either positive LSI for calcium clouding or a measurable filter problem (high pressure, short cycle, visible bypass).
• Brown: brown cast with positive metal test or obvious sediment source; metals confirm with a copper-iron drop test.

Remediation

• Green: bring FC to the algae-kill level appropriate for the measured CYA (the higher the CYA, the higher the FC needed to stay effective), brush all surfaces to break the biofilm loose, run filtration continuously, and clean the filter repeatedly as dead algae loads it. Verify CYA is in range; dilute if over-stabilized so the chlorine you add is actually active. Retest until FC holds overnight with no loss, the standard proof the bloom is dead.
• White: correct the driver. For calcium clouding, lower pH and bring LSI to neutral or slightly negative so carbonate redissolves, then filter. For filtration failure, deep-clean or replace cartridge media, recharge DE grids with the correct powder charge, or rebed/backwash sand, and run a clarifier or a small floc to aggregate fines so the filter can catch them. Run continuous circulation; white haze rarely clears on a timer-limited run.
• Brown: for metals, sequester first to hold them in solution and prevent staining, then partial drain and refill to lower concentration and run the filter. For stirred sediment, vacuum to waste (or to the filter if light) and let circulation settle and clear what remains. For organic tannins, oxidize with chlorine and filter, repeating as the load breaks down.

References

• CDC Model Aquatic Health Code, disinfection, water clarity, and turbidity guidance.
• PHTA/APSP-11, Standard for Water Quality in Public Pools and Spas (clarity, sanitizer, and balance targets).
• Taylor Technologies, Pool and Spa Water Chemistry, algae, metals, and saturation index.