SWG issue?

aaron_w_o

Bronze Supporter
Apr 15, 2018
201
ottawa, ontario, canada
Pool Size
40000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-20
Hi, not sure what's going on last few weeks, but here goes (will use imperial since I know most of the membership are USA based).

10,500 gal inground pool.

About 2 weeks ago, system started telling me salt was high. So, every day I let off about 2" water and replaced with city water from hose. Checking ppm each day and coming in at 3650ppm, down from about 4400ppm. took 3-4 days to do this. Target was 3400ppm. I was happy that I was close enough. Why was I even doing this? well, I read that salt too high can cause FC loss due to basically lack of efficient Cl generation. My FC was consistently low most of this summer, right around 2.

After 2 days at "in range" salt levels, I checked my FC and there was still not much progress. I then tested my CYA... very low(30ish). Got it up in range (60) with a bucket of stab(2lbs).
Very next day, FC was up (nearly 5!). I figured, OK I've got the system functional again, I will back off the power to the SWG (it was at 80%, so I dropped it to 50%).

1 week went by, and I was busy and didn't mess with the pool much. Last night I did a big maintenance (brushed walls, vacuumed thoroughly, cleaned all screens and baskets and filters). We are having a nice hot weekend and I wanted a clean pool :) During my maintenance, I did water testing. FC back down at 2! (more like 1.5). Checked salt. SUPER LOW? 2500ppm. WTF! LOL.

Added 40lbs of salt (1 bag). Poolmath actually asked for almost double that, but I don't like to add too much of anything in 1 shot.
Woke up today (it's been 12 hrs since salt addition). Sensor says salt is still only 2750. didn't come up much. 250ppm.

what is my question?

well... does the SWG provide accurate readings, and if yes, does it take hours or days for mixing and readings to stabilize?

The pool water itself is quite clear, and there was a minimal amount of algea in 2-3 spots as I brushed the walls last night. The pool gets full sun from 10am to 5pm.
It's been warm up here...86F for days with humidity quite high.

(PS- my pH is always very very stable at 7.5-7.7)

Is my salt reading playing games with me? is my swg failing? is this just a function of super high UV and me not knowing the "ropes" about how to add and measure salt?

insights, ideas & suggestions welcome.
 
wow, that's quite an elaborate instruction there for diagnosing & troubleshooting. thanks!
am thinking i should probably use my chem tf kit to test salt vs using the pentair measurement.
also, perhaps take a sample to a store to see how close my own "lab" work is... in the past I have seen that the tf100 is perfectly in line with what the pool store measures.

I should have added another comment to my post. weekdays, the pump (and thus SWG) runs 7pm-7am (due to metered elec discounts). weekends it runs 10am-10pm. I am wondering if I should be running it longer and maybe not only at night for the 5 weekdays.

or am i kidding myself and do i need to start taking things apart, splicing wires and buying parts ? :p
 
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