New pool balancing for first time, FC is high

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D

dsm1212

0
May 4, 2017
19
Massachusetts
Ok, so new fiberglass pool after filling and running SWG for a couple days I had FC=1, CYA=0, PH=8.2, CH=0, TA=50. Test kit is K-2006C. Initially I lowered PH to 7.6, added CYA, added calcium, bumped SWG from 50% to 65%.

Adding the solid CYA required running the pool for 24 hours (instead of the usual 12). I'm cautious about the CYA so I added about a 3rd of what it called for and it increased to 20, but FC spiked to 14 (yikes!). Even though it doesn't smell or feel super strong, I don't want it this high. Was that entirely from running the SWG so long at a higher rate or is there some compounding effect from adding CYA?

So then I added more CYA, more calcium, and lowered the SWG to 35%. FC the next day was 12, but I have not done other tests yet. Today I turned the SWG to 0%, sun is strong so maybe it will drop FC. Will retest tonight, I expect CYA to be 40-50 and calcium about 175, but here is what I had at last test. Where to go from here? Poollogger suggests CYA in the 70-80 range, but I see other places say 30-50. What's best?

thanks

steve

FC12
18 hours ago
CC
0​
2 days ago
PH
7.6​
2 days ago
TA
70​
2 days ago
CH
90​
2 days ago
CYA
1220​
2 days ago
Temp
82°​
2 days ago
Salt30502 days ago
 
I'm in Mass as well and I keep my CYA at 80 per TFP recommendations. At that CYA level, the FC target is 6, with a minimum of 4, and a shock of 31. FC of 12 isn't terribly high, and given the heat/sun we're having today and no SWCG output, my guess is that will be gone in a day or two if you don't turn the SWCG back on. Not sure your equipment, but I run my IC-40 at 100% for 11 hours a day, and depending on usage, that keeps FC up fairly well. High bather load or multiple days without the solar cover, and I need to supplement with bleach.
 
A couple extra thoughts: it would help others if you are able to provide the specifics of your pool, such as size in gallons, filter type, and especially your SWCG model / size. We've deduced it's saltwater and you mentioned fiberglass, so those are covered, but putting them all in your signature would help. The 30-50 vs. 70-80 CYA variance you're seeing is dependent upon chlorination method. For a saltwater, TFP recommendation is 70-80 CYA -- see this page. The jump you are seeing in FC might be your SWCG, but without knowing its size relative to the size of your pool, it's hard to say. Adding CYA will slow the UV degradation of your produced FC, so yes, you would expect to see a slowdown of FC burnoff with higher CYA levels. But the raise you mention is fairly dramatic for a SWCG alone.
 
To set your SWCG, unless you have data from using liquid chlorine on daily FC requirements, I would start at 2 ppm FC per day needed from the SWCG.

Your SWCG can create 1.4 pounds (22.4 oz) of chlorine gas each 24 hours. With a pool of 9255 gallons (wow that is exact, did that come from paper work on the FG pool, if so, it is less than that as that is assuming full to to the top of the FG flange) you would need 2.6 oz of chlorine gas per day. So you would need to run your SWCG at 100% for 2.6/22.4 or just under 3 hours per day.

Use liquid chlorine to get your FC at target, then run your SWCG as above and if it holds at target, you are great. If your tested FC (test same time of day each day) goes down, run the SWCG longer, if it goes up, run it shorter.

Hope that helps.

Take care.
 
Thanks, yes 9255 was the manufacturer :). My installer said he thought it was about 8700 gallons so maybe he is right. Tested last night (see below) and made no changes today (SWG still at 0%). I'm out of calcium but I'll add some more CYA tomorrow morning and recheck FC and CYA tomorrow night. And pick up some more calcium for the next day.

thanks
steve

Results from poollogger.com

FC: 14
CC: 0
PH: 7.6
TA: 70
CH: 110
CYA: 40
Temp: 83
Salt: 3050
 
Numbers are fine other than CYA still low as you note for a saltwater pool. That said, obviously something is off in the testing, which isn't likely a big deal given the levels we're referring to. But if your SWCG has been at 0% for the past 1.5 days since you registered 12 FC, and you've not supplemented with another chlorine source, either your 12 FC as of 1.5 days ago was a misread, or today's level is a misread at 14. There's no way (I'm aware of?) for FC to go *up* on its own without some chlorination method. Again, you're well above your minimum and target at your CYA level, so it's not a huge deal, but just something to consider in testing -- if no chlorine has been added, the +2 FC is suspect. You'd expect that 12 FC to fall 3-6 FC in 1.5 days under normal conditions.
 
Ha, when I posted that I had set it to zero it was misleading, I had just set it to zero and if you see in the posting the FC12 was from 18 hours prior to that. I had still left it on that prior night so the SWG had run for ~18 hours at 35% after the FC12 test before I lowered it to zero. Having said that it was a full day of zero before I tested it and got the 14 again. I think maybe from what someone else said here that if I run for 12 hours a day I probably only need it at 20-25%. I'm going to see where I'm at tomorrow night. Hopefully it will be down to something reasonable. Landscapers are doing coping right now and I stayed away from the pool tonight.

thanks

steve
 
I had my water tested at the local pool store just to see where I'm at and there was one discrepancy with my own testing (CH) and with my SWG. So this is what the pool store gave me:

Results from poollogger.com

FC: 6.3
CC: 0.1
PH: 7.9
TA: 63
CH: 129
CYA: 69
Temp: 80
Salt: 3600

My own tests match this except for CH, I tested at 165. I'm not sure who is right, but I was reading 110 previously and I added 4 lbs of calcium, the result I measured was consistent with what I added. But I did add 2 inches of water to the pool after doing that test so maybe it diluted enough to drop to 129?

The one thing I am concerned about though is my SWG shows salt level at 2850 but the store tested it at 3600. I can taste the salt in the pool and my pool installer had come back and added salt when the SWG was so low after the initial install. At the time he was surprised it was low. Could the SWG be faulty?

steve
 

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I seem to be in good shape now. My pool installer did a couple of tests on my salt level and it matched the SWG. My pool installer did a great job except for water balance. He just pumped in some water and dumped in the salt and left. Thanks for the startup help!
 
Considering the garbage or badly measured/unnecessary chemicals that most installers dump in, you probably got lucky. :)

Make sure if it's new plaster you have enough muratic acid on hand to keep the pH under control and lots of brushing!
 
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