Is it time to replace my Hayward T-Cell 15?


New member
May 9, 2012
I am having an ongoing problem this season with my Hayward T-CELL 15 keeping up with chlorine production. This is my 9th season with the pool (vinyl liner, 87500 litres) and this chlorinator. In years past, I run the pump 11 hrs a day with the SWG set to 20-40%. Over the previous two seasons I had increase the SWG from the 20% to 35% and then 40%. However this year, I have had to increase my pump run time to 12 hrs a day and the SWG to 90% just to keep chlorine around 5ppm. As a test, I dropped the SWG to 85% on Friday and tested the water on Sunday and FC was 3.5ppm. (It was a hot weekend with many people in the pool). One other item of note is that just before 11am this morning, I checked the Diagnostics menu and it showed the chlorinator was turned off as the % was met. Considering the pump turns on at 7am, and from my understanding, with the SWG set to 85%, it should be running 85% of the 12 hour runtime which would not be 11am in the morning. Am I understanding this correctly? Or does it run 85% of each hour?

Once I turned the SWG back one the diag readings are as follows:

Readings (Taylor 2006kit):
FC: 4ppm
CC: <.5ppm
PH: 7.4ppm
TA: 75ppm
CH: 300 ppm
CYA: 40 ppm (working on raising this to 70ppm)

I have cleaned the cartridge filters recently as pressure was reading high. I have backup filters that I use when opening the pool when the pool comes back from winter. I have cleaned each set of filters twice so far since May which is uncommon. After initial opening and first cleaning, I usually get away with cleaning the filters once more throughout the season. The pool was quite green this year after winter. I wasn’t thorough in the fall removing leaves as I should have been.

I am trying to determine if I have invisible algae or if my T-Cell is has reached it’s lifespan (or perhaps another issue?). I recently inspected the cell, soaked it in water / muriatic acid as per recommendations. I may have noticed that one of the grills in the cell looked paint chipped. If I recall, the grills are white with one looked like I could see metal in a small spot. No obvious build up on the cells.

I have been following the TFP methods since I built the pool and my water after initial balance is usually quite consistent. Throughout previous summers, the only real balance I have to do is lower PH from 7.8 to 7.4 every 2-3 weeks and adjust the chlorinator (+5% or so) as the temp rises during the summer months.

From what I am reading, 8 good seasons with this cell may be as good as it gets but since I am diagnosing this myself, I don’t want to sink money into a new cell if that is not the issue.

Thanks for any suggestions.


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Considering the pump turns on at 7am, and from my understanding, with the SWG set to 85%, it should be running 85% of the 12 hour runtime which would not be 11am in the morning. Am I understanding this correctly? Or does it run 85% of each hour?
The Aquarite uses a 3 hour cycle. So at 85%, it would be generating for 153 minutes, then idle for 27 minutes. Then repeat.

I would suggest you do an Overnight Chlorine Loss Test
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TFP Expert
Mar 2, 2011
For AquaRite, move the switch from auto to off and check all of the readings.

Move the switch back to auto and recheck the readings.

Move the switch to off for a minute and then back to auto and recheck the readings.

Report all readings.

What are the first seven characters of the cell and box serial numbers?

What is the actual salinity and how are you measuring it?

What is the T-cell size?

Is the T-cell size set correctly in settings?

To get the performance percentage of the cell in each polarity, divide the instant salinity reading in each polarity by the actual salinity reading.

For example, if the instant reading is 3,300 ppm and the actual salinity reading is 3,300 ppm, then the salt cell is working at 100%.

However, if the actual salinity was 3,800 ppm, then the performance percentage is 86.8%.

Anything over 75% is acceptable.

At75%, or lower in either polarity, it's time to consider replacing the cell.

The instant salinity in both polarities should be about the same (+/- about 200 ppm).

You need to be really sure about the actual salinity reading.

You need to use a K-1766 salt test kit or a calibrated meter.

K-1766 Taylor Salt Test

Note that ProLogic, AquaLogic and AquaPlus use the Hayward T Cell.

However, the procedure to get the diagnostic readings is different.

Here is the procedure for ProLogic, AquaLogic and AquaPlus:

Go to the diagnostic screen, note the readings and then press the + button to reverse the polarity.

When the new numbers appear, see what they are.

Then, press + again and note the new readings.
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