Intellichlor IC-40 salt level rising

[TonyAl]

The salt level appears to be rising on it's own! I converted my pool to salt about a year and a half ago and had no problems until the end of June when the high salt indicator came on. Pool store tested salt level at 4800, so I drained and refilled about 750 gallons to lower salt to 4500. High salt indicator went off and everything was fine until yesterday when the high salt indicator came on again. I have not added anything except pool acid during that time. When I first installed the SWG in April 2014 the salt level at startup was approx 3000. What could be causing the salt level to rise?

Today's test results:
Temperature = 87
Ph = 7.4
FC = 7.0
TA = 70
CYA = 40
Ca = 700
Borate = 47
CSI = -0.12

Would the high calcium hardness cause a false high salt reading? Also, CYA was at 70 at the beginning of July, I'm surprised to see it disappear so quickly is that typical in Phoenix or could it be caused by the solar heater or something else? Should I even worry about it or just keep adding more to keep it around 70?

 

[ping]

The IC-40's do not have temperature compensation and when the water warms up there is an error in the actual salt reading. The warmer the water the larger the error will be. Right now your salt level is high and when a SWG can not make temperature compensations it leads to high salinity errors. The solution will be to drain the pool to lower the salinity level until the SWG is happy.

Raise the CYA back to 80 ppm. Usually every year I need to add 30-50 ppm of CYA and this is in a pool with very little water loss due to anything other than evaporation. I have a feeling the solar panels have something to do with it.

As far as to why the salt level increases you might want to check the salinity of your fill water. It should have some salt in it and since you are in Phoenix you might be adding a lot of fill water. Also, any bleach you add it will also add some salt. In 5 years of use, I have only added 80 lbs. of salt, but I do add bleach every now and then.

 

[TonyAl]

Thank you for the detailed response. I had not considered that the fill water would be adding salt, the pool store dudes say nothing can cause the salt level to increase, but you are right. The water quality report for Phoenix indicates that the salt level is between 75 - 150 ppm. And with the pool being in direct sun all day, quite a bit is evaporating.

When I first converted to salt, my salt level was at approx 3100. The high salt indicator comes on at 4500. Pool calculator shows it would take about 150 pounds of salt to raise the salt level in my pool by 1400. I did the math, and the volume of fill water that would need to evaporate to add 150 pounds of salt would be 12,000 to 25,000 gallons using the info from the city water report. Surface area of my pool is 390 square feet. The City of Scottsdale has a chart showing evaporation rate for a 400 sq foot pool, after adjusting it to my pool size the evap rate is 19,172 gallons per year. From the time I first filled the pool and added salt (salt at 3100) until the high salt indicator came on (salt at 4500+), the evaporation chart shows I would have evaporated just under 26,000 gallons of fill water. So it all adds up.

I drained and refilled 1000 gallons this morning and the high salt indicator is off. Never thought I'd need to be draining and refilling so much water every couple months. Looks like I need to figure out a way to divert rainwater to the pool.

 

[pooldv]

That is very interesting. Thanks for posting that feedback.

 

[Semi-retired]

Yes, interesting bit on the effect of fill water. I generally have the opposite problem here in FL. I periodically have to drain after large thunderstorms and/or tropical storms. This dilutes chemical concentrations over time and I end up having to add both salt and CYA. I think I like my situation more though....a bag of salt and some stabilizer costs a whole lot less than 20,000 gallons of water, lol.