green algae cannot be erradicated

[p0las]

Hi,
I have been fighting green algae every year with variuos level of success. Swimming season is slowly starting here in Australia and I'm losing the battles already...
I have an old 65000L concrete pool. It is covered with a floating blue (bubble wrap type) cover, practially all the time (water still too cold to swim). I vacummed and cleaned it after winter a few weeks ago. Of course it turned nasty after I stirred it but I managed to clean it in a week or so. Each time I uncover it on weekend, the water is nice but there is algae on the walls and the bottom. Sometimes not really visible until I brush.
For the last week I had really high chlorine levels to shock it. 15-20ppm all the time, never dropped. The pump has been running for 8h a day. CYA is really low at the moment (10-20 max) to make the chlorine as active as possible and PH was stable and under control (7.5 this morning). When uncoverer today I thought I finally eradicated the green little monsters. However when brushed I can see green clouds after each bruch stroke again.
Not sure what to do next. Keep the high chlorine going for another week?
Maybe this is normal when there is no automated cleaner preventing algae from attaching to the walls and the bottom?

PH 7.5
CYA low: 10-15
chlorine: 20

 

[billyghawaii]

I'm wondering how long is pool filter on in a 24 hour day?

 

[billyghawaii]

Oops I saw that you run the filter on for 8 hours a day... Have you tried longer times?

 

[mknauss]

Follow the SLAM Process process. Raise your CYA to at least 30 ppm, leave the cover off so the CC can dissipate, and run your pump 24/7 until you pass the three criteria as listed in the article. Use the shock level shown in [FC/CYA][/FC/CYA] based on your CYA.

 

[p0las]

thank you guys. I will try the cover off with higher cya. I like to have the cover on as it heats the pool really quickly and we can start the season early. cheers.

 

[tim5055]

thank you guys. I will try the cover off with higher cya. I like to have the cover on as it heats the pool really quickly and we can start the season early. cheers.

You do NOT want to raise the CYA until after you have eradicated the algae utilizing the SLAM Process process.

 

[p0las]

That's what I thought tim5055. I kept my CYA low and chlorine levels even higher than in the SLAM. I guess the brushing every day is the missing component.

 

[tim5055]

That's what I thought tim5055. I kept my CYA low and chlorine levels even higher than in the SLAM. I guess the brushing every day is the missing component.

What test kit are you Using?

If you don't have a quality one, pick up one here Clear Choice Labs Simple. Accurate. Fast.

Total Pool Water Testing Kit, Salt Water Clear Choice Labs

 

[domct203]

PH 7.5
CYA low: 10-15
chlorine: 20

Following the SLAM Process procedure, lower pH to 7.2 and raise CYA to 30ppm in preparation for the SLAM.

Before you do anything, do you have a proper test kit to complete a SLAM? How do you test?

 

[p0las]

yes, I do have a test kit. lots of vials and chemicals. I have been brushing the pool every morning and this plus high chlorine and low CYA seems to be working. I did raise Cya and will check the levels tomorrow. I don't expect it to be more than 30 though.
Next rain will screw the balance and I will start again... seems to be the pattern ;-)

 

[domct203]

yes, I do have a test kit. lots of vials and chemicals. I have been brushing the pool every morning and this plus high chlorine and low CYA seems to be working. I did raise Cya and will check the levels tomorrow. I don't expect it to be more than 30 though.
Next rain will screw the balance and I will start again... seems to be the pattern ;-)

The only thing rain is going to do is make you wet. Unless you get a monsoon, rain has very little effect on pool chemistry.

Does your test kit contain a FAS/DPD (drop count, no color matching) chlorine test? Can’t properly perform the SLAM without it.

 

[p0las]

My pool is flushed with the ground. Once the soil is saturated with water I get a fair bit of runoff that turns my pool into a pond very quickly.
I do have FAS/DPD set. The chlorine drop was minimal. I was away for the weekend and brushed green stuff again this morning... I'm going to start SLAM again (I allowed chlorine drop to 7 thinking I was done with it before weekend)

 

[triptyx]

ahh - if you're getting runoff into your pool, yes, that will cause huge problems every time.

Is there any way you can trench or otherwise redirect that excess water so that it doesn't run into the pool? You're not going to have a very good time keeping it clear if you're getting yard runoff into it!

 

[Dirk]

Consider covering your pool only at night. That's when you lose most of the heat. Let the sun shine on it (UV)! Let your pool breathe (CCs). And until you figure out how to stop flushing your garden into your pool, I'm gunna say you're never going to have a TFP. French drains, retaining walls, redo the decking and/or grading to slope away from the pool (as it was supposed to be built in the first place), etc.

That, and taking a good look at your pool maintenance routine. If you keep organic matter out of the water (brush and vac and filter), and maintain a proper FC/CYA ratio ([FC/CYA][/FC/CYA]), you shouldn't be getting algae. If you cheat the TFP method, and/or don't keep your pool clean enough, it won't work. You have to keep your FC above the appropriate minimum FC for your pool, not necessarily the TFP recommendation, every minute of the day, every day.