Returned from 17 days vacation: green algae???

[opeth771]

Hey guys,

I went in France for 17 days and when I came back, I found my water to have a shade of green on some spots so I went outside to take a look at the water. There was some green algae patches on the bottom of the pool....

I just did a water test and here are the results:

FC: 5
CC: 0
CYA: 40
TA: 100
PH: 7.2

If my FC is at 5 which is ideal for SWG, then why do I have algae? And how is it possible to have algae if I don't have CC ? There is obviously something I don't understand... Could it be just the filter? I did a backwash and it was pretty dirty...

I just brushed the pool and the water got a bit darker but nothing too bad.. Should I slam it? Any explication as to why this happened?

Thanks

 

[LFrankow]

I would perform an Pool School - Perform the Overnight FC Loss Test (OCLT)
Perhaps a SLAM is in order, most likely.
Once things go back to normal I would raise your cya level to 70, after the slam not before.
My swg out west here just will not keep up with 50 ppm cya when it gets hot out.

 

[opeth771]

I would perform an Pool School - Perform the Overnight FC Loss Test (OCLT)
Perhaps a SLAM is in order, most likely.
Once things go back to normal I would raise your cya level to 70, after the slam not before.
My swg out west here just will not keep up with 50 ppm cya when it gets hot out.

Ya but wouldn't my FC be lower if it was the SWG not keeping up? Seems to me like it is keeping up right now. There is something I don't get here

 

[AftonJeeper]

It could be pour circulation. With no activity for that long it is possible some areas of the pool did not get chlorinated water flowing into them. That is why we brush our pools one and a while.

 

[LFrankow]

Ya but wouldn't my FC be lower if it was the SWG not keeping up? Seems to me like it is keeping up right now. There is something I don't get here

Yes but did it all of the 17 days you were gone?
Could be as AftonJeeper said circulation issues.
I myself would do the OCLT just for piece of mind.

 

[opeth771]

Yes but did it all of the 17 days you were gone?
Could be as AftonJeeper said circulation issues.
I myself would do the OCLT just for piece of mind.

But for now I should slam it right?

 

[LFrankow]

Remain calm
Do your OCLT first, if you fail that SLAM

 

[tim5055]

But for now I should slam it right?

If you have visible algae, start the SLAM Process

 

[opeth771]

If you have visible algae, start the SLAM Process

Started the SLAM process yesterday. Water became clear again today. PH jumped to 8.0 though.. Any explanation of how this happened?

THanks

 

[AftonJeeper]

Once you raise FC over 10 pH test is unreliable and will read falsely high.

 

[mknauss]

pH test is not accurate with FC above 10. Do not waste your reagents testing it.

Take care.

 

[jturie]

Just went through this process myself....except that the pool literally turned on me overnight. Pool looked a bit cloudy to me the previous night, and then the next morning I looked out and ....bam...green algae all over the bottom. SLAM and brushing for a couple of days took care of it. I managed to do this before I discovered this great web site. The trick is to not let up, or the algae will come right back.

 

[tim5055]

Just went through this process myself....except that the pool literally turned on me overnight. Pool looked a bit cloudy to me the previous night, and then the next morning I looked out and ....bam...green algae all over the bottom. SLAM and brushing for a couple of days took care of it. I managed to do this before I discovered this great web site. The trick is to not let up, or the algae will come right back.

Not to hijack the OP's thread, but it is valid for them also--- This is what happens often. The heart of TFP pool care is learning your pool. A higher chlorine consumption, water not quite a s "sparkly" and you know something is wrong. If you catch many of these issues quickly you will find a day or two of elevated chlorine cures the ills.

 

[Swampwoman]

Any explanation of how this happened

Who looked after your pool while you were gone?
How many hours was your pool set to filter daily and how many hours of your runtime is your swg set for?
Were there any power interruptions while you were gone?

Any chance any one used your pool excessively, eg a party, whereby the chlorinator might have fallen behind for a few days on keeping up?

Lastly, the presence of CC or lack thereof does not actually mean anything with repect to algae. CCs just mean the chlorine has combined with urea or ammonia to form chloramines. Adequate FC levels usually eradicate CCs. So the presence of ccs is a symptom of an under-chlorinated pool, but do not directly related to algae per se.

 

[Akathisia]

The thing I've learned about having a SWCG this summer is to keep my target level 2-3 ppm above recommended levels to avoid days that it would otherwise drop below the minimum. It gets hot and windy here and lots of stuff blows into the pool. It requires a one time addition on bleach and the SWCG still puts out the same amount. When I go on vacations I will probably bump it higher just to be safe.