Need some help, cell possibly failing?

Cephrael · Jun 28, 2022

So, my t15 cell has been having some issues this season. Constantly showing inspect cell and low salt. I tested using a Taylor k1766 and it’s at 3400. So I know its not low salt. The instant reading is around 3000 but dips to 2800 occasionally. The average has been 2700 lately. I took it off and let some 4-1 MA/water sit in it for about an hour. There is some rust colored staining on the pvc. some of it came off after the cleaning.

Cell was installed in 2019 and after some experimenting has been running at around 70% for 12 hours a day. provides just enough chlorine to my pool. Is it dying or is something else wrong? I’d like to avoid dropping almost a grand on a new one. Thanks.

Texas Splash · Jun 28, 2022

According to your Poolmath logs, it looks like your FC has dropped quite a bit in teh last week or so. Have you done an Overnight Chlorine Loss Test just to ensure the SWG isn't competing with algae?

Cephrael · Jun 28, 2022

So I had just finished SLAMming the pool, and had everything good. OCLT was .5. FC was holding steady at about 3.5. Then i went a couple days of not checking, life got in the way, and I noticed it dipped. Checked the generator and it was showing check cell and low salt and hadn’t been producing the whole time. Dumped 2 gallons of shock in to bump chlorine back up, cleaned the filter thoroughly (Only backwashed during and after SLAM) and it looks like it was working fine all day.

Texas Splash · Jun 28, 2022

Cephrael said:
Then i went a couple days of not checking, life got in the way, and I noticed it dipped.

Bummer. It happens. I'm actually diagnosing my own cell issues. So here are my thoughts of what you may want to do before dropping a bunch of coin:
1. Another Overnight Chlorine Loss Test. You have tp rule out algae first.
2. Do an SWG GAIN test. Use the PoolMath APP (Effects of Adding) to find out how much your cell "should" produce during x-amount of hours at night. With no competition from the sun, and a previous OCLT (passed), it's all about the cell. For example, say your FC is 5 at bedtime and your cell set at 100% for 7 hrs is expected to product 4 ppm. Then after 7 hrs your FC should have risen to about 9, perhaps only 8 since we accept 1 ppm loss of FC on any given night. But if your FC didn't move, or only climbed by 1-2 ppm when it should've gone up by 4, you know there's a problem.

Cephrael · Jun 28, 2022

Texas Splash said:
Bummer. It happens. I'm actually diagnosing my own cell issues. So here are my thoughts of what you may want to do before dropping a bunch of coin:
1. Another Overnight Chlorine Loss Test. You have tp rule out algae first.
2. Do an SWG GAIN test. Use the PoolMath APP (Effects of Adding) to find out how much your cell "should" produce during x-amount of hours at night. With no competition from the sun, and a previous OCLT (passed), it's all about the cell. For example, say your FC is 5 at bedtime and your cell set at 100% for 7 hrs is expected to product 4 ppm. Then after 7 hrs your FC should have risen to about 9, perhaps only 8 since we accept 1 ppm loss of FC on any given night. But if your FC didn't move, or only climbed by 1-2 ppm when it should've gone up by 4, you know there's a problem.

I’ll give that a shot. Thanks.