SWG Cell Failure in Progress?

[poolneophyte]

I have been following the TFP methods since my pool was installed in 2007. I now have seven successful seasons behind me and have a good understanding of water balance and chemical requirements. I have been unhappy with the Jandy Aquapure SWG and PDA control system since the beginning and have replaced several circuit boards and flow sensors over the years but still have the original SWG cell. This season, I noticed that I have needed to increase the SWG percentage over prior seasons to achieve the same chlorine level at a given CYA level. I have no error messages and the SWG appears to be operating normally. I have also confirmed that the salt level displayed on the SWG is accurate by using a digital meter calibrated for salt.

So, if organics are ruled out by a OCLT, is it safe to assume that the cell is beginning to fail or is reaching its end of life? Is this normally how they fail?

 

[mikemass]

If you got 7 years out of a salt cell I would call yourself extremely fortunate. But based on your 2007 build year, doesn't that make this your 10th season? (assuming you count 2007) Which is almost unheard of for the cell's life.

Some fail overnight. Some deteriorate over time. Some still produce but at a lousier rate. Some do not read the proper salinity any more. You can look into getting it tested, but based on the age and what you are describing, might be time to consider buying a new one.

 

[poolneophyte]

That was a typo. The pool was installed in 2009 and which makes seven seasons through 2015. Given my poor history with Jandy equipment, I'm not sure if I want to invest $500 or so in a new cell or just just cut my losses and spend less on a Stenner pump system. My problem with Jandy equipment is that every circuit board, sensor, etc. is a couple of hundred dollars. They are also unwilling to help a pool owner diagnose and replace boards on their own. I have been through 3 or 4 tri-sensors already and every one of them has been a different design. Eventually, they may get it right but only at the cost of the consumers.

 

[ping]

Make sure the cell is clean of scale as that can cause it drop in production. Most likely you are nearing decision time on a new cell or not. I haven't heard of too many issues with the lastest tri-sensor design.

 

[poolneophyte]

I haven't checked for scale but will take a look tonight. Have never had any scale at all in the prior years and the water has always been balanced to Jandy's requirements.

 

[poolneophyte]

Just to rule out organics, I ran an OCLT on Saturday and it passed. The only other possibility besides cell failure is that our CYA level is less than we think. I then compared our records from the last couple of seasons and noticed that we added more CYA in prior years than this year. We tested the CYA again today and got 55 which is low for the SWG. Today, we added enough CYA to target 75 to see if the FC level goes up thereby allowing us to reduce the SWG percentage. If that doesn't do the trick, I have nothing left to conclude but cell failure.