New pool owner, SWG related question

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J

josh1014

Member
Mar 9, 2019
23
Maryland
Hello, sorry in advance for the long message!

This is my first full season with my new pool in Maryland. I have been having some issues maintaining proper FC levels. I have a pool and spa, both of which have auto covers. Pool is ~33,000gal, spa about ~2500gal. I have all Jandy products, including the nature 2 fusion soft SWG (for which I have never installed or used a mineral cartridge, only the SWG). My pool construction finished last August so I only got about 2 months of usage with 60s-80s ambient temperature. I successfully kept the pool balanced with the CYA level in the low 30s and a target FC of ~1ppm since the pool is covered at all times when not in use. Pump run time is 8a-8p, 11 hours of pool time and 1 hour of spa time, and my SWG was set at about 45% for the pool and 30% for the spa, with minor adjustments based on usage. Everything was easy!

Fast forward to this year, I tried to employ the same strategy and found that my pool always had 0-0.5FC. FC always equals TC and the pool always looks great. All other parameters are all normal range including salt level. First, I gradually cranked up the SWG run %, but this didn't help. I inspected the salt cell which looked pristine, and confirmed that it was in fact producing chlorine by doing a Taylor test of the water coming right out of the return (it was). I ran the SWG continuously for 24+ hours with cover closed and did get my pool up to FC of 1ppm. So.. everything works. I figured, maybe with ambient temps in the 90s and sun exposure, even with the cover closed, maybe the sun and heat was still burning out all my chlorine faster than I could make it and I need more CYA. So, I boosted my CYA to 50. I am now running the SWG at 80% for pool and spa. Spa has gotten to FC 0.5-1ppm with this, Pool is still <0.5.

Am I missing something? It just seems odd to me that even though this is my first season dealing with July weather and 90+ deg heat, and even running my SWG twice as long with a CYA level 15-20 points higher than last year, I'm still failing to maintain FC ~1ppm like I could with ease last year. Again, the pool looks perfect and the TC always equals the FC, so nothing is in there eating up chlorine. I've gotten in the habit of dosing the pool with liquid chlorine (1/2 to 1 gal) after a gathering, and when I check the next day, I'm usually at 1-2PPM FC and TC, but then after a few days go by I'm back where I started. I know in general I'm doing lower target CYA and FC than most because my pool is covered at all times when not in use. Do I really need to run the SWG 100% of the time during this time of year, or extend my pump run time? I just can't quit figure out why things are so different than they were last year and feel like I'm missing something obvious.

Thanks for those of you who took the time to read this whole story!
 
Welcome! :wave: Looks can be deceiving, and I suspect that's the case with your pool. Water looks good, but no FC or very little that you have had is a recipe for algae even if you can't see if. Excessive organics is FC's #1 enemy. I also think you placed to much reliance on the cover, and now you can see that increasing the CYA to protect water from the sun (already covered) isn't helping.

My first recommendation would be to perform an Overnight Chlorine Loss Test. Do you have a TF-100 or Taylor K-2006C test kit? Your signature doesn't show your pool info or test kit, so I'd also be sure to update that. But do the OCLT if you have one of those test kits to see if you have excessive organics eating chlorine in the hours of darkness. Follow the OCLT page carefully to do it right. Let us know how that goes so we can help you further.

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Josh, I neglected to mention that with the FC so low at the moment, you need to increase it right away. I'd push it up to 5-7 ppm with liquid chlorine or regular bleach right away. Test again to ensure it made it there before starting the OCLT with the SWG OFF. Then pull your second water sample early tomorrow to see the results.

Thanks @Mike1162 :goodjob:
 
Thanks for the response Texas Splash.

I ordered a Taylor K-2006 kit yesterday and will have it in a few days. All I currently have is a lesser taylor kit that only lets me approximate FC up to 5ppm, and test strips that approximate up to 20ppm. I saw your message yesterday morning and figured the most reasonable thing to do to help the situation and collect more data was to shock the pool.

Like I said, it still looks crystal clear with no visible build-up or algae anywhere. I added 3 bags of cal-hypo shock, which took the FC to 20+. I added it at 9AM which I know is not the way to do it, but I had it on hand so why not. I left the pool uncovered all day. By 1:30P, FC was down to ~3ppm. I checked it every 1-2 hours from then on, and it maintained at 3ppm all the way until I closed the pool cover at 8PM. I have had the SWG off since adding the shock. I just checked at 7AM today and the FC level appears to be 1ppm.

Admittedly, I'm currently relying on rough data, but my presumption is that a combination of UV and organics quickly took care of all the shock and knocked me down to 3ppm which was maintained against the ongoing UV exposure by my CYA. If the pool was still dirty, my FC would have plummeted to 0 correct? The fact that it stayed at 3ppm for 7 more hours is a good sign? Is the ultimate drop off down to 1ppm over night within expectation or still indication of a hidden algae problem? I will of course do a true OCLT once I have the FAS/DPD test, but any additional thoughts or suggestions for now? Thanks so much for your help!
 
Definitely a big drop in FC, but we'll help you through it. Getting that K-2006 will be a HUGE help. Just keep doing what you're doing for now and we'll get you back on track once the kit arrives. I wouldn't worry too much about an OCLT until you have the K-2006 which comes with its own FAS-DPD for very accurate testing. By the way, the Taylor kit usually gives instructions for FC testing with a 25ml water sample. We recommend a 10 ml water sample size as follows:

10 ml water sample with ONE generous scoop of powder (should turn pink). Start mixing and add drops until clear. Divide result in half to get FC. Example: 20 drops to clear equals an FC of 10.
 
So I got my K2006 kit. Nothing really changed after the shock treatment I mentioned above. Maybe the first day or two was slight better, but ultimately I drifted back down to 0-0.5 FC with 80% SWG run time. I added some liquid bleach yesterday and measured 3.5 FC via FAS-DPD 45 minutes later. I closed the cover overnight, checked this AM and was at 1.5 FC... so a failed OCLT.

My plan is to SLAM the pool tomorrow AM. Any reason I can't start with 6 bags of cal hypo shock, and then use liquid bleach for the rest of the process? Just because I have it on hand.

Is the conclusion here that I've probably had low levels of algae for a couple months now, and I just haven't noticed any visible growth, cloudiness, sliminess, etc because the SWG constantly providing chlorine and the cover constantly depriving the algae of sunlight has kept it at bay this whole time? Thanks for your help!!
 
SLAM in progress, results so far:

SLAM target FC 18

7:30am- 6 1lb bags of 73% calhypo added (theoretically bringing FC to 18)
9am- FC 12 - 0.5 or less CC. 2 gallons of 10% liquid chlorine added
10:20am-15.5 FC - 0.5 or less CC. 1 gallon of 10% liquid chlorine added
11:30am- 15 FC - 0 CC. 1 gallon of 10% liquid chlorine added

At what point do I stop adding chlorine and just roll into an overnight OCLT to confirm I'm finished? If in another hour I am back at 15 FC and 0 CC again, is it fair to assume that my losses are just coming from UV and not organics?
 
The water has been crystal clear from even before I started the SLAM process, so I’ve met 2 of 3 criteria the whole time. I don’t want to drag this out onto multiple days if I can avoid it, so my question was just how many more rounds of topping up the FC to 18 with 0 CC present before I can safely call it quits and wait to confirm the morning OCLT?
 
If your pool water is really crystal clear - and I suggest you look at the thread - then do the OCLT tonight.
 

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Final results:


7:30am- 6 1lb bags of 73% calhypo added (theoretically bringing FC to 18)
9am- FC 12 - 0.5 or less CC. 2 gallons of 10% liquid chlorine added
10:20am-15.5 FC - 0.5 or less CC. 1 gallon of 10% liquid chlorine added
11:30am- 15 FC - 0 CC. 1 gallon of 10% liquid chlorine added
1:10pm- 12.5 FC - 0 CC. 2 gallons of 10% liquid chlorine added
2:50pm- 12.5 FC - 0 CC. Nothing added
4:40pm- 11 FC - 0 CC. Nothing added
7:20pm - 10 FC - 0 CC. Nothing added
COVER CLOSED
7AM Reading - 7 FC - 0 CC

So this is a failure of the OCLT, but I’m confused. Aren’t there other variables to consider than just algae, again considering I’ve never seen any definite evidence of algae. The water temp during this process was 95 degrees with ambient temp 95-98 degrees. With a CYA of about 45, isn’t any FC in excess of about 5-7 pretty unstable, perhaps even more unstable with such a high water temp and ambient temp? I lost about 1 FC in 3 hours at the end of the day when UV index was trending down to 1. Sunset was at 8:40p, extrapolating that through the rest of the night as UV falls to 0, plus considering minimal organics oxidized on the underside of the autocover, is a drop of 3 FC from a starting point in excess of the target range for my CYA still a failure? Do I need to repeat the OCLT from a starting FC of 7 or less, or is the conclusion here still that I need to restart this whole process? Is it odd to have 0 CC for basically 18 hours of testing and still conclude there are more organics to kill?
 
Failure of the OCLT = Organics growing in your pool. Its that simple. SLAM’s are measured in days, not hours. Get your pool at SLAM level and keep it there for several days. Pass 2 OCLT in a row and then keep your pool at SLAM level for one more day to be sure.

Then keep your FC level based on the FC/CYA chart.

You wont get any other advice around here. TFP is a method. Follow it and you will have a great pool.

Or just do whatever you want, its your pool. But you wont get any positive reinforcement for anything other than the TFP method.
 
josh1014 said:
Final results:


7:30am- 6 1lb bags of 73% calhypo added (theoretically bringing FC to 18)
9am- FC 12 - 0.5 or less CC. 2 gallons of 10% liquid chlorine added
10:20am-15.5 FC - 0.5 or less CC. 1 gallon of 10% liquid chlorine added
11:30am- 15 FC - 0 CC. 1 gallon of 10% liquid chlorine added
1:10pm- 12.5 FC - 0 CC. 2 gallons of 10% liquid chlorine added
2:50pm- 12.5 FC - 0 CC. Nothing added
4:40pm- 11 FC - 0 CC. Nothing added
7:20pm - 10 FC - 0 CC. Nothing added
COVER CLOSED
7AM Reading - 7 FC - 0 CC

So this is a failure of the OCLT, but I’m confused. Aren’t there other variables to consider than just algae, again considering I’ve never seen any definite evidence of algae. The water temp during this process was 95 degrees with ambient temp 95-98 degrees. With a CYA of about 45, isn’t any FC in excess of about 5-7 pretty unstable, perhaps even more unstable with such a high water temp and ambient temp? I lost about 1 FC in 3 hours at the end of the day when UV index was trending down to 1. Sunset was at 8:40p, extrapolating that through the rest of the night as UV falls to 0, plus considering minimal organics oxidized on the underside of the autocover, is a drop of 3 FC from a starting point in excess of the target range for my CYA still a failure? Do I need to repeat the OCLT from a starting FC of 7 or less, or is the conclusion here still that I need to restart this whole process? Is it odd to have 0 CC for basically 18 hours of testing and still conclude there are more organics to kill?
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How clean is the cover? Could that have algae on it? Try doing an OCLT without covering. At night, turn off SWG, test once it's dark and again early in the morning. If you pass the OCLT, the cover may be the culprit.
 
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