High chlorine but still have algae

[cpd515]

The chlorine in my pool is at 4.0 ppm, yet I recently noticed green algae on the wall of my plaster pool. Why would this happen?

 

[jblizzle]

What is your CYA level? For that matter, post up a full set of test results.

 

[JohnT]

4ppm is not high chlorine.

 

[NoPool4U]

If your CYA level is really high, you need more chlorine to combat algae. That may be your problem. Some forms of powdered chlorine will increase your CYA level. I just recently experienced this when switching from liquid chlorine to powdered chlorine based on a pool store recommendation I should've known not to take their advice; luckily I caught it relatively early.