algea again

[BobW0295]

over a week my pool went from sparking clear to increasingly hazy. then I started to see green algea on the bottom. I have been diligent on keeping my levels correct. (FC between 2 and 6)
Last nights test
FC 5.0
CC O.O
PH 7.5
CYA 50
ta 110

pool calc said shock level is 16 and to add 160 oz of 12% shock. that took me to 21 and held it for two hours, CC still tested at 0.0. I could not retest till this evening due to work but I ran the filter for 24 hours. this evening the water looks much better but still some green stuff on the bottom.
Tonights test. shows FC at 9.0 and CC 0.0 PH held at 7.5.

What I dont understand is the CC being zero.
also I was only running the filter for 8 hours a day and had not backwashed for about 3 weeks since the flow was still good.
I have many friends and family in the area with pools and they do not have the frequent problems I do. They keep the PH right and add chlorine Nightly. The difference is they all have DE filters and I am running sand.

 

[JasonLion]

With CYA at 50, for day to day use you want FC between 4 and 8, and never below 4. If you allowed FC to go down to 2, that was too low.

CC at zero is common enough. There isn't always any CC, even when there is a full fledged algae bloom in progress.

This doesn't have anything to do with having a sand filter, it is about consistently maintaining the correct FC level.

You should be brushing the entire pool every day while at shock level.

 

[Butterfly]

I have been diligent on keeping my levels correct. (FC between 2 and 6)

I think this may be the culprit :grrrr: FC values for 50 CYA are between 4 & 8, and never below 4.

Continue to shock until you meet the three criteria to be done shocking (red lines in my sig).

 

[BobW0295]

Water is crystal clear, pool looks good, but still seeing light algea where wall meets bottom, only visible to me because I know where too look. Some dead algea still evident on the bottom. I only need to vacuum about 1x / week and backwash about every 2,
Latest numbers

FC 4.0
CYA 45
TA 80
ph 7.2

Adding about 2 ppm of 48% cal hypo per day
PH needs lowering about 1x / week. I think the water looks clearer with the ph closer to 7.2 than 7.8.

Any suggestions?

 

[Beamup]

Have you done an OCLT?

 

[duraleigh]

Any suggestions?

The visible presence of algae means you should shock the pool.....according to the VERY specific directions in Pool School. Continue to shock the pool until algae is no longer visible and you pass the OCLT....it is really that easy! :lol:

 

[BobW0295]

About 2 weeks ago I shocked and passed the ONFC test with no CCs.
I am going to shock again