Question about poolcalulator results - CSI

[gilbee]

I've got a question about the poolcalc:

If I setup the calculator for troublefreepool.com, SWG, and plaster, then use the goals that are above the various blanks, it seems that the CSI ends up in the "potential to become corrosive to plaster" at .52, which is almost at the magical oh noes .6 .....I used the following mostly fictitious numbers:

FC 4 (calc says 4-11 is goal, but this isn't used in the CSI calc)
pH 7.5 (calc says 7.5-7.8)
TA 80 (calc says 60-80)
CH 260 (calc says 250-350)
CYA 75 (calc says 70-80)
Salt 3200 (calc doesn't say anything, but 3200 is around what I expect most people to have for salt content with a SWG)
Temp 70 degrees


When the water is properly balanced, are we basically riding the edge between balanced and potentially corrosive, more toward the potentially corrosive?

 

[chiefwej]

Notice that your CH is at the low end of the range, your TA at the high end, and pH low end. That combo yields a CSI on the lower end of the acceptable range. Change any or all within the stated goal area and the resulting CSI will also change.

 

[gilbee]

Ok, let's cut them down the middle:

pH 7.6
TA 70
CH 300
CYA 75
Salt 3200

this yields -.45 , still in the "potential to corrode plaster" range

If I take them all to their max of the goal range, I get .13, which results in "balanced".

How worried about keeping my CSI in the balanced result should I be? My plaster already has pieces missing from it in a few places on the floor, and will need resurfacing soon, but I'd like to not help it along in the failing process...

 

[Richard320]

I think you're worrying too much. Plug all those numbers in and see what happens when the water warms up. CSI moves positive. Your CH is going to climb through evaporation and refilling. Is it low now? And unless you obsess on it, your pH will drift upwards and spend a few days approaching 7.8 or sitting there before you lower it. That also drives CSI upwards.

 

[gilbee]

My CH at present is 250, which is the same as my fill water except when it rains of course, which happens a LOT here.

 

[JasonLion]

"potentially corrosive" is not a problem unless the water moves into corrosive. So you have to look at what is likely to change the CSI while you are not paying attention. In this case just about everything that might happen is going to raise CSI and there is no way it is going to go into corrosive unless you add acid (or something similar) to the pool.