New cell didn’t fix lack of chlorine 5 gases found in the environment

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I have a 11000 gallon in-ground pool with the Apure 700 salt system in Orlando, Florida that is inside of a screen enclosure. Last summer I had a difficult time maintaining chlorine in the pool. The salt cell came with the house when I bought it 3 years ago so I don’t know how old it is but it was able to hold a chlorine level during the winter while the pool was not used (I did run the pump/Apure daily). With it warming back up, I went ahead and purchased/installed a new cell package (cord, cell, flow sensor) last week. After a week of extended pool pump operation there is NO CHLORINE RESIDUAL in our tests. Chemistry is perfect (pH, salinity (3.5k PSU), stabilizer (70 ppm) no iron or hard water). We brought a sample to the pool store and they confirmed all the chemistry (pH was a bit high at 8.0). I have not added salt to my pool this year and the conductivity isn’t changing. I checked all of the voltages (front board, back board, cell) to the manual yesterday and confirmed they are all within specifications. I held onto my old cell and, with the old cell filled with pool water, plugged my operating pools DC power cord to the cell (demand 0). When I raised the demand the cell started to create bubbles and gas off, which I’m told is what you would expect to see with the system working properly (breaking up the Na from the Cl). I swapped the cells (uninstalled new cell from the pool system) and tested the new cell with the same results (gassing when power applied) There are no error codes and flow is indicated. I have been running the pool for 12+ hours a day @ 100% demand for the past week now and the conductivity and chlorine readings don’t move. The pool has surprising remained clear although it was a little cloudy this morning. There are no alarms being misses (no audible alarms) and the service light is not illuminated. Everything looks and acts like it’s supposed to with the exception of the fact I’m not making chlorine. The pool heater (solar) has been in service and the pool temperature is 84F. There has been light recent pool usage (1 person for half hour per day on weekends without sunscreen).

Thanks all for the feedback so far. I do want to add a couple of points. The night before I sent my post I did clean my cartridge filter (which was green (I had previously cleaned the filter 3 weeks prior so not a neglected task)). I also cleaned my strainers of any leaves and other organics.

The morning I sent my post I did shock the pool. So in response to a couple of you, mission accomplished regarding getting chlorine back in the pool. When I got home after shocking, my pool was crystal clear and I showed 3 PPM free. I have the ability to measure chlorine using test strips and titration and I used the strips last night just to ballpark where I was. At this point I don’t think the Overnight Chlorine Test will do anything for me but that suggestion is saved for a later time (like in a few days when my residual is flatlined again).

What worries me the most is the fact that I have not added salt this year and yet my conductivity hasn’t moved from 3.5. I have double checked only one pool sample at the pool store (a couple of days ago) and they confirmed the conductivity number. Maybe it’s dumb luck on the timing but the old conductivity cell and new conductivity cell read the same. One other head scratching note is the temperature readout on the old cell is the same as the new cell, both reading about 94F which is no where near what the actual temperature (pool heater off, actual temp closer to 80F).