Green pool, help

Macuick

Member
May 19, 2017
11
MS
Test results as of today: fc 11, cc .5, ph 7.2, alk 100, cal 0 Why is my pool green

27' semi-inground, vinyl liner, aluminum walls, 26", Outdoor pro 26" high rate sand filter, pentair model 320 in-line chlorine feeder, 2.0 hp two speed pump (outdoor pro)
 

Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
4,590
NW Ohio
Well there's a few things it could be. First, what is your CYA level? You forgot to put that up. Second, how are you testing? It takes accurate data to make an accurate diagnosis, so we need to know the source of the data.
 

Macuick

Member
May 19, 2017
11
MS
yes. I think I found the culprit of algae. Took the ladder out of the pool and it was full of algae on the inside. The ladder was used, we soaked it and cleaned thoroughly or so we thought. Have taken ladder out and I guess the next step is to slam the pool. Going to test again, make sure it balances, vacuum, brush then slam. Correct?
 

Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
4,590
NW Ohio
If the test doesn't come up to the 100 line, then your CYA is well over 100 ppm. That's why you have algae, there's so much CYA in the water that even 11 FC isn't enough to kill it faster than it can reproduce. Unfortunately that's a side effect of using pucks for chlorination.

You're going to have to drain and refill at least 70% of your water to get the CYA in a position where you can reasonably follow the SLAM Process.
 

CrystalRiver

Well-known member
Jun 19, 2020
313
Massachusetts
Calcium 0 and CYA under 100 is highly unlikely if you've been using pucks. If the water was lower than the 100 line, that means your CYA level is over 100, and you need to do a dilute test. Mix your pool water with an equal amount of tap water before putting it in the mixing container and adding reagent. Then do the test, and whatever number you get, multiply by two.