Pool Problems: Green, Cloudy, Chlorine Issues Fixed

Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.

What does your water look like?

Start with what you can see or smell, then confirm it with a test. A strip is fine for a first look. A drop kit is better when the numbers decide a big dose.

What you notice	Most likely cause	Start here
Green or teal water, slimy walls	Algae: chlorine fell below the minimum for your CYA	Green pool recovery plan
Yellow dust, dark spots or pink slime in corners	A specific algae or bacteria type	Identify the algae type
Milky or hazy water, can't see the drain	Low chlorine, high pH or calcium, or weak filtration	Cloudy water diagnosis
Test reads zero every morning	Hidden algae, low CYA, or heavy use	When chlorine keeps disappearing
Test color is off the chart after a dose	An overdose, or a shock that hasn't worn off yet	Chlorine too high
Strong "chlorine" smell, red eyes	Chloramines (combined chlorine)	Chlorine smell and red eyes
Suds along the waterline	Algaecide, soaps and lotions, or soft water	Foamy water
Brown, green, or blue stains; clear water turns green after shock	Metals (iron, copper)	Metal stains
Storm just passed	Dilution, debris, and lower pH	What to test after rain

Green and algae

Algae grows when chlorine drops below the minimum for your stabilizer level. Clearing it usually takes more than one dose: shock as your product's label directs, brush the walls and floor every day, run the filter 24 hours a day, and test chlorine morning and evening until it holds overnight. Mustard, black, and pink growths behave differently, so identify the type first. The minimum chlorine for your CYA is on pool chlorine levels.

Cloudy

Cloudy water has a short list of causes, and the order you check them in matters. Chlorine comes first because early algae looks like haze. Then pH, alkalinity, and calcium (scale can cloud water), then the filter. The cloudy water page asks six questions in that order. If the test shows high pH or alkalinity, fix it with how to lower alkalinity. If pH is low, see how to raise pH.

Chlorine problems

Chlorine can be too low, too high, or right on the number but still "smelly." If it drops too low overnight, that points to algae or missing stabilizer. If it is too high, you usually wait instead of draining. If you have just shocked, go by the test result, not the clock: test, and swim only once FC is at or below the limit on your product's label (often 4 ppm). More on how long to wait after shocking.

Other: foam, stains, smell, after rain

Salt water pools have one more possible cause: a scaled or worn cell makes less chlorine than its setting suggests, so see cleaning a salt cell before blaming the water. For hot tubs: chemistry in a small, hot tub goes wrong faster, so use the cloudy or green hot tub page instead of pool doses.

Every page here gives amounts as estimates from our open formulas. Always follow the product label, and never mix chemicals.

Pool water problems and fixes