Problem keeping FC up (SWG trouble?)

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tlhwxman

tlhwxman

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Mar 30, 2012
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Okay folks more trouble. It's been about 1 month since I properly shocked the pool and started testing the water properly. I am in fairly good balance (see number below). I am still having alot of trouble keeping my free chlorine up. I have been trying to dial in my SWG percentage to balance the loss from daytime sun.

Just to give you some background, when we moved into the house last fall, I ran the pump 8 hours/day with the SWG at about 40-60%. This maintained the FC just fine. Since the winter (and into the Spring) it has been nothing but trouble. I am running the pump for 8 hours/day and the SWG is running 90%. I still lose FC to the tune of 4 PPM a day (although that varies a tad). After finding this site and reading, I assumed it was because all the water was out of balance and CC was high (and that was certainly a factor before I shocked). However, with the water now in balance I am stumped as to the cause. Is is bad cell?? ...

Well, I took the SWG to the Pool store, they said it tested fine. I checked the voltage/amperage on both polarities - looks good (as far as I can tell). BTW - I have Hayward/Goldline Turbo Cell (T15)

Here are the numbers if curious.
FC 1.0 ppm
CC 0.0 ppm
pH 7.2
CYA 65
TA 70
CH 200
Salt 3300
Temp 72F

Incidentally, last Fall when the SWG was at 40% the pH, CYA, CH and TA were all in the same range.

Any ideas? Help!!

Todd
 
If you are losing 4ppm FC daily, that's not outrageous but probably indicates you have some organics in your pool.

You are not keeping your FC nearly high enough with a CYA of 65, your FC should vary between3-5ppm but 1.0ppm is not enough

Shut the SWG off in the evening and perform the OCLT (see Pool School)

If you fail that test, you will need to shock the pool thoroughly (Pool School again)
 
You probably have a low level algae problem, enough algae to consume chlorine but not enough algae to be visible. I suggest raising to shock level and through brushing while at shock level until you pass an overnight FC loss test. Then, when algae is ruled out, raise the CYA level up to 80. Between those two steps you should be able to cut your chlorine consumption significantly.
 
I should have specified that the FC is NOT an overnight loss. I have been periodically checking the overnight loss. By periodically I mean once or twice a week. It has never been above 0.5 (mostly 0.0) since shocking 1 month ago.

I went back into my spreadsheet and actually calculated the loss. My l4ppm number was a bit off. The actual daytime loss is is 2-3ppm.

Todd
 
2-3ppm seems pretty normal. But, since you have clearly not kept the FC level in the recommended range, there is a chance that something is trying to take hold. Get your FC up on the high end of the recommended range (using liquid chlorine) and keep it there ... may have to supplement with liquid occasionally if the SWG is not keeping up.

Also, bumping the CYA up as Jason suggested may help as well.
 
Okay - your responses sound logical. But there are details I am leaving out. I should be thorough in my explanation...that is my fault.

I have had trouble keeping the FC level up, but that dose not mean I have let it stay low. I have been supplementing the FC with Bleach to get the levels backup immediately upon testing.

Also, the shock that was performed a month ago was a 12 day process that followed the book to the letter. Overnight chlorine tests were perfectly clean coming out of the test and since the test. This problem has been ongoing before the shock. But what is really telling is that was occurring immediately after it too.

Listen, I hear you guys. It could be algae taking hold. Or maybe the shock never got rid of it all. I can certainly try another shock, but something seems weird.

Thoughts,
Todd
 
I know you got the cell tested (I know nothing about how they do this ... are they more reliable testing the cells than testing our water ???).

Out of curiosity, how old is the cell?
What does the SWG think the salt level is?
 
Great point Jason. I'll be honest, I don't trust the pool store that tested the SWG. They have steered me wrong before. The previous owners bought the pool in 06 and it is the original cell as far as I know. So it is 7 years old.

The SWG says the salt is 3200 (test strip says 3300). Also the volt/amp output is +_26 V and +_6A give or take a few.

I should note, that the cell was cleaned when it was tested.

Todd
 

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Well, having the salt readings match is a good thing. It seems like when the cells start to go bad they start reading lower and lower salt levels. 7 years is actually pretty impressive as anecdotally (word???) they seem to last 3-5 years.

When the cell is "generating", try taking a water sample from a return and you should find a significant FC level.

How long ago was is cleaned and tested?
 
The plot thickens. The cell was cleaned just before the shock (just over a month ago).

Perhaps you guys were on the right track. Maybe the algae is still there.

Frustrating...
 
Okay - here comes the part where I feel like a complete Rear. :)

I was just digging around on the message board and think I may have a handle on the problem. We have been periodically adding Ascorbic Acid. I knew that Chlorine ate AA, but didn't realise they eat each other.

Question - if you dump in AA about how long can the effects of that linger (with respect to eating FC)....few days??

Todd
 
I think you are on to something there ... the ole Mutually Assured Destruction of AA and FC.

Not sure how long the affects last, but I am sure is has something to do with the amount of AA you have added.
 
In order for theory to be right the effect of AA would have to last for days. I went back and looked at my testing log and it seems when we add AA the drop in FC goes on for days afterward. That is, we add AA and FC drops the next day. I then add Bleach to raise it, then it goes back down on day 2...etc...etc.

I am not 100% convinced that is the problem. However, it is the most likely option at this point. I will take a better stab at sequestering the metal and stop adding AA. Let's see if that works

Todd
 
I tried the return test. I took a hose from the return and measured the FC. It was 5ppm higher than the base pool level!!! I am guessing the SWG is not the issue. So I will move on from that theory.

Have not added any additional AA in over 5 days. I am running the SWG for 8 hours at 90%. This is barely holding on to the FC level of 5ppm. Again, OCLT is showing no loss. CC levels are 0.0 to 0.5. CYA at 75 now.

Given the high output of the cell, that still makes me think something is going on. Still can't get a handle on it.

Here are the new numbers if curious.
FC 5.0 ppm (10ppm at return with SWG on)
CC 0.0 ppm
pH 7.2
CYA 75
TA 70
CH 200
Salt 3300
Temp 76F

Todd
 
Sandy,

Yes. As best I could figure, the Ascorbic Acid effects on FC lasted about a week to two weeks. Slowly over time I began adding FC from the SWG as the AA wore off. I could then drop the percentage level on the SWG.

I guess this is why they recommend adding FC back in slowly after an AA treatment. I certainly learned a lot in this process.

Hope all goes well on your end.

Todd
 

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