Sodium vs. potassium?????

[Mesamav]

I have a good friend that is SLOOOOOOWLY converting to BBB. He seems to like it when I get involved, he then promptly disagrees with me because the pool store said something different, he then does it their way once and when it doesn't work out, he finally tries my way which then works out just fine.
With that said, we are having a couple of issues with his pool and I wanted to get the experts take on things.
His pool is 14000 gallons, SWG, plaster with a very slight pebble tech finish and a DE filter.
We filled his pool with tap water but we have been using softened water as fill water and this leads to my question.
His pool started to get some green along a few spots on the walls and the opening for the skimmer was covered in a slimy green but his water is still sparkling clean. He has had his pool since last September and we haven't had any problems until now. In December, he drained the pool and had it acid washed. Refilled with tap water and all is well until now.
When he refilled, he forgot to put CYA in there. He is in Mesa Arizona so there is LOTS of sunshine and plenty of heat so with no CYA, I'm guessing his SWG is working overtime.
So this morning he asked me to come over with my fancy test kit and check out his pool. Everything looks great but when I test the CYA and tell him it's well below 20, he tells me he didn't put any in when he drained it.
First thing? We are off to Leslies for some liquid CYA. Dump it in and I'll test again next week. With the amount we put in, it should bring the CYA level to 35 or 40 give or take. I'll test and bring it up to 60 or 70 in smaller increments.
Now we have CYA but what led to all this was his SWG is saying the salt level went UP from 3200 to 3900. No salt has been added since December and the salt level went up. I'm confused how this can happen unless it's from the water he is topping off with. He has a softener that uses potassium instead of sodium. He uses the softened water to keep his calcium levels in check because we have extremely hard water here.
Sorry about the long rant but at least you know what's going on.
A couple of questions.
Is the potassium chloride making the salt levels rise?????
We drained quite a bit of water but the levels aren't going down. Does CYA add salt?

Thanks......

 

[chem geek]

What the SWG is measuring is conductivity. The water softener is exchanging calcium for two potassium so that would be close to a wash for conductivity since it's roughly proportional to charge and you have an equal charge swap. The CYA will increase conductivity since the dominant species is the singly charged cyanurate ion, but you didn't add that much (in ppm sodium chloride units it's a factor of 2.2 lower than the CYA ppm level).

However, the temperature went up and that will increase conductivity, though most SWG systems have temperature compensation for their salt readout though technically they really care more about actual conductivity. Conductivity of sodium chloride solutions increases at roughly 2% per ºC so going from a 50ºF pool to 80ºF would be 30ºF or 16.7ºC so a 33% increase in conductivity. The SWG reported a 22% increase in conductivity which would correspond to a 20ºF temperature rise if this were not compensated.