Algae after 3 weeks of non-use?

[DivingIn]

I was away from my pool for three weeks. I use the trouble-free method and never have any problems.

When I took the solar cover off upon returning home, the water looked fine, but there are several large light-gray or light-green blotches on the bottom of the pool, both in the shallow and deep ends.

The water tested:
TC and FC: 5
pH: 7.1 (it was 7.5 three weeks ago)
TA: 100
CH: 200
CYA: 20

While away, I used a chlorine feeder to keep the chlorine up. I normally don't use the feeder. I like to keep the CYA down.
The pump was on 10 hours a day during the 3 weeks. We live by many trees, and there were a lot of leaves at the bottom of the pool - scattered everywhere.

Are the splotches algae? I didn't think it could form with the chlorine at 5 or above the whole time.

Thanks for any help.

• 17,000 gallon in-ground
• Vinyl liner (new last year)
• DE filtering
• Sta-Rite pump

 

[jamis]

Welcome! Where in Toledo? I've been having a tough time the last couple of weeks with what I first thought was silt. Then it became algae which I cleared with a SLAM. I'm being told that we are having a higher than normal algae problem in our area by several different pool companies. I'm also seeing a collection of pollen in the pool overnight this week. It's been really dry around here this month with July being over 2 inches behind in rainfall. There has to be a lot of dust, and associated chemicals in the air right now. After three weeks under the solar cover, what was your water temperature? Did you vacuum to waste and did the splotches return?

 

[tim5055]

An OCLT will let you know if it is organic. Raise it up to shock level after the sun goes down and test to verify your FC. Test again in the AM before the sun gets on the pool.

 

[DivingIn]

Thanks. I'm in Point Place. The water temperature was 86, although it is 82 now.

 

[jamis]

Thanks. I'm in Point Place. The water temperature was 86, although it is 82 now.

So am I. Shoreland area. I've had mine uncovered since the breakout two weeks ago. Temp's at 80. Don't forget, we are downwind from the Hoffman Road Landfill. Lots of dust from that thing lately.

 

[Donldson]

Welcome to TFP! I am down near BG, good to see another NW Ohioan.

How is the circulation of your pool overall? It is possible for areas to have lower FC levels if the circulation isn't very good. When nobody is swimming the bottom can potentially be that place.

An OCLT should give you an idea. Regular sweeping or brushing will help keep things mixed while we wait for swimming weather to hopefully return.

From myHTC One via Tapatalk

 

[DivingIn]

There is only a skimmer and a return - no drain or outlet at the bottom of the deep end (8 ft). I was thinking that too, but some of the splotches are in the shallow end by the return.

I'm wondering if the chlorine just wasn't enough while I was gone. After a pound of calcium hypochlorite, the FAS-DPD test showed 7.2, while the test strips indicated well over 10. Maybe what I thought was 5 was really 2 or 3.

- - - Updated - - -

So am I. Shoreland area. I've had mine uncovered since the breakout two weeks ago. Temp's at 80. Don't forget, we are downwind from the Hoffman Road Landfill. Lots of dust from that thing lately.

I'm in Shoreland too.

 

[Casey]

Your pool does NOT need Calcium. Use Bleach.

ABC's of Pool Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool
Chlorine CYA Chart
Recommended Levels
What is Trouble Free Pool Care?