Can't keep FC up with SWG

[KentC]

I am really struggling with keeping FC up to target levels even with very high CL generator settings. I hope you can guide me to a solution.

Several months ago my pool began a slow increase in required CL gen (installed March 2019) settings from normal 20-30% up to 90% now. Supposedly this system should handle a pool 3X the size of mine. Phosphate level has always been zero. Nitrate results are hard to read but seemed to be 15 at a peak so I pumped out and replaced about 4000 gal. When that didn’t help, I SLAMed the pool April 11. I overshot CL to 34ppm and it stayed above 28 (with CYA of 70) for two days and it took 9 days to drift back to 10ppm. I am trying to maintain 8-10 (per a chart printed from TFP page) but am close to maxing out the generator. It dropped from 8 to 7 in 24 hrs at 80%. I have cleaned the cell several times in the last three months and as recently as 2 days ago. Visually, it appears to be generating normally. Pool is crystal clear and no sign of algae. Lots of, what I assume are, calcium flakes being blown out of one return. This is new in the last 6 weeks with all test levels essentially unchanged.

Latest results:

FC= 7.0

CC= 0

PH=7.2

Borate 50

TA=75

CH=400

CYA=70

Phos=0

Nitrates=5-10

Nitrites=0

Salt=3700

Water temp= 85-90

CSI= -0.15 per Taylor Watergram

All chemicals and test strips are still within dates.

Unfortunately, I will be gone the next 8 days and hope to keep the pool from turning green while I am gone. Suggestions would be greatly appreciated.

10K gal, plaster, 3hp IntelliPro VS
SolarTouch controller, AquaCal Heat Pump, Solar cover in winter
CircuPool digital RJ30+ SWG, 150 sq ft Posi-Clear cartridge filter
K-2006 Test Kit, Location-East Central Florida

 

[Texas Splash]

This is where I would start:
1. Perform an Overnight Chlorine Loss Test. Say all you want about water looks good, but algae isn't always visible to the naked eye. Pass an OCLT first so you know algae is out of the equation.
2. Check your SWG for scale. Since you already observed flakes, there may be more in the cell.
3. Those are an interesting grouping of test results. Are they from your K-2006, or something else? Store testing and test strips are unpredictable at best.
4. If you do need to do a SLAM Process, be sure to follow it to the letter until you pass all 3 criteria.

Unless your SWG is malfunctioning, chlorine goes to two places - organic material and the sun.

 

[TexEdmond]

test strips

We don't recommend using those here.

If you've cleaned your cell that recently, it's probably okay. I notice your CYA level is on the low end of our recommendations for SWG pools. Being in Florida you're probably getting a lot of sunlight on a really warm pool. I noticed the same issue getting things balanced for summer here... SWG wasn't keeping me at 7ppm FC which is where it seemed to want to settle last season. I had dipped 10ppm CYA and didn't realize it. Now that I've got that replenished, I'm back running the SWG lower.

Trichlor tabs would be my recommendation, because it'll be killing four birds with one stone while you're on vacation. First, it'll help keep pH low, it'll slowly bring your CYA levels up, it's effective at preventing algae growth during unmonitored times, and it'll give your SWG a little help while your CYA increases. Plus you've got borates which will also help fight algae growth.

 

[YippeeSkippy]

Stop cleaning the cell UNLESS you actually see white cement looking stuff on the plates. If you do it with acid you're removing the special magic coating that makes the chlorine production happen.
You may be shortening the life of the cell.

 

[wireform]

Step #1 is a real test kit such as a TF-100 pro which has everything you want and need. I wouldn't add any CYA not having solid evidence of real chemistry levels.

 

[PoolStored]

I am trying to maintain 8-10 (per a chart printed from TFP page)

Might re-read the page. For CYA of 70 with SWCG, your target is 5. FC/CYA Levels

 

[TexEdmond]

Might re-read the page. For CYA of 70 with SWCG, your target is 5.

I gotta agree with OP on this one. If it's safe to swim up to SLAM levels, why run things so tight with only 2ppm of wiggle room?

 

[PoolStored]

I gotta agree with OP on this one. If it's safe to swim up to SLAM levels, why run things so tight with only 2ppm of wiggle room?

Tex, you are, of course, correct. Great catch. But targeting 10?

He was quoted the LC chart, don't want others to get confused.

 

[KentC]

Thank you all. I will have to tackle this after I return.
The only store test was to satisfy the Circupool guy who didn't trust my zero phosphate result and it matched mine. SeemsTF-100 has the same tests as the K-2006??? What is the distinction? Test strips are only for salt, borate, and nitrates. Phos is separate but not a strip.
I followed the SLAM to the letter and easily passed the OLCT.
I must have found a non-TFP endorsed chart to SWG targets. I thought that they sounded high.
Later,
Thank you all.

 

[PoolStored]

You were quoting TFP, but it was the Liquid Chlorine chart, not the SWCG chart. @TexEdmond is also correct, nice to have a bit of room, and some run a bit higher than the SWCG reco of 5 in case of variable demand on a day. Maybe 7? I just think 10 is high and not necessary.

 

[TexEdmond]

But targeting 10?

He was quoted the LC chart, don't want others to get confused.

Totally. That's getting into the "running the SWG longer to just keep up with the extra FC burning off because there's too much FC in the pool already because the SWG is running too much" zone. A Florida pool with tons of sun might want to live in the 80 CYA / 10 FC happy zone. Only one way to find out... Hey OP we have a little chemistry project for you when you get your real test kit after vacation...

 

[PoolStored]

Totally

Ok, learn something new every day.

 

[Mdragger88]

The k2006 is fine - same regeants
So stick with those numbers for making adjustments.
Since cya is no longer in question you may want to put a few tabs in a floater for insurance & raise to /near slam level with liquid chlorine as insurance for while u are away. (I always do this for vacation) Leaving the settings as is & run an Overnight Chlorine Loss Test upon return. Are u currently running the pump 24/7?

 

[TexEdmond]

Ok, learn something new every day.

Yeah I might need to check my math on that, but I believe I have heard here that FC loss is a function of FC / CYA level along with the usual culprits like organic content, bather load, temperature. The higher the FC levels get over recommended levels, the more burns off. It's obviously a much bigger deal if you're paying for bleach, but it's still wise not to make the SWG work harder than it needs.

 

[TexEdmond]

Test strips are only for salt, borate, and nitrates. Phos is separate but not a strip.

Right you are, I stand corrected. Most folks here don't worry here about phosphate and nitrates, so that can save you some test time unless there's a specific need.