Question re: FC Usage in Green Pool

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W

wkener2

0
Feb 14, 2014
30
Atlanta, GA
All,

Hope everyone is well and ready for the swimming season!

I have a quick question: I've been doing the TFP system for a couple of years now. I just started SLAMing (used to be shocking) my pool Monday evening. Ran the pump for one hour and tested using FAS-DPD kit, CYA did not even register (considered it 0) and of course FC was zero. I added 4lbs of solid CYA and enough bleach to get to 15FC. What is weird is that the pool is not consuming FC at the rate I am used to... normally when I do this the FC goes back to 0 in the first hour and I have to use a ton of bleach to keep it at shock level. It is now almost 48 hours later and I have only used about ten 121oz bottles of bleach and the pool is still green, it even looks like algae is still growing on the steps? I bumped up the FC to 20ppm yesterday, but I only lost 5FC overnight. It feels like something is going on as this is taking longer than I am used to... also, pump is running fine and I have backwashed about three times when the pressure gets really high.. any thoughts?
 
Welcome aboard, and glad you joined us.

You're on the right track right now, but just starting on this. You may be used to more Chlorine demand (not good that you are) but this is plenty. Your filter is clogging from Algae or whatever else is in there. This took a while to happen, so it will take some time to clear. I would bump the Cya another 10 PPM since you should be around 20 with that dose. Figure, and do that but don't worry about re testing it. If you are following SLAM, did you adjust pH before starting?
 
Have you brushed the pool? If it is green you definitely still have algae. It can take a long time to complete a SLAM I would scrub the pool and see if FC has more loss. Do you have a TF 100 kit? Keep adding bleach as often as you can.
 
Patrick,

That is what has me confused... if my CYA is low then FC should be used up faster, especially in direct sunlight, correct?

No, I was lazy when I started SLAM:( I was out of the re-agent for the PH test so I only tested FC and CYA. Do you think I should let the FC come back down and retest everything? Here is a pic after 36 hours of SLAMing: 20150429_104740.jpg
 
How much more FC demand do you want? Be glad of what it is. If you tested correctly, which I'm assuming you did, then don't worry. It looks like you have some shade there, so that helps. As for the pH, where do you think it was? If you don't think it was close to right, then I would suggest that you adjust it once the FC comes down to follow proper procedure.

Also, and this is speculative, but if this has happened before, you may have had demand from Ammonia, and just don't this time. No worries. :cheers:
 
I actually do think you need to get an accurate read on the PH and make sure it's about 7.2 so the FC can do it's job better.... Are you certain about the CYA level? what environmental conditions were you in when you took the test?
 
Frustratedpoolmom,

CYA test was performed in full sunlight with sun at my back. There was almost zero diminishing of the black dot at the bottom of the tube... I am second-guessing the CYA level now because this certainly feels like there is not enough FC in the pool, but the CYA would have to be 50ppm or higher for that to be the case and its just not possible... I only added 64oz after the initial test. Does an unusually high Ph prevent FC from acting effectively on algae? Also, I found two small metal pails in the pool that had begun to rust... should I be concerned?

Thanks for all the help!
 
Yes, you want the pH down if you think it's high.

I would expect to see Zero Cya in this pool or close. Very common. If the test came out like you describe, then you have no CYA. Trust your results.

You may have rust stains from the pails sorry.
 

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I took a water sample to Leslie's to have them test CYA just for kicks... test result was 0. If that is correct then my testing was good. The 64oz I added Monday wouldn't register on the test yet, so my actual CYA should be around 20ppm. So, if you guys were me, would you let the FC come down in order to test the Ph or just stay the course with the SLAM? What level does the FC need to come down to to effectively test Ph?

Thanks!
 
It's actually better for FC. Higher temp water actually drives it out faster. As far FC function is concerned you'll lose less of it in terms of speed at lower temps, so that's a good thing. Lower temps also inhibit Algae growth, but below 50F is where it is significant.
 
Update: Have not added any bleach since midday yesterday per Patrick_B (letting it drop to 10ppm to check Ph), but FC has only dropped to 15ppm (loss of about 6-7ppm in 24 hours) Pool is still green but it is lighter and clearing (see pic). The lack of FC consumption still has me baffled, but I won't add any more bleach until I can test the Ph. Brushed entire pool again this morning, used leaf rake and am now getting very little debris....20150430_110214.jpg
 
I would expect more loss in 24 hours in this condition, but I can't explain it I'm sorry. If you are confident your did the test correctly then it is what it is. I hate telling you to wait for pH, but this should have been adjusted prior to starting. I would suggest brushing a lot, and keep filtering while you wait. This should help at least a little, and the brushing needs to be done to dislodge any attached Algae.
 
Hopefully this afternoon's sun will help get the FC down to 10ppm so I can test for Ph... the filter has been running 24/7 since Monday evening except for backwashing and I will brush again tonight. Shame on me for not doing the Ph test before SLAMing... I am quickly learning that there are no shortcuts!
 

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