High Ph - CSI question

[cobra46]

Hi All,

I am having trouble understanding my CSI. In general I do understand what CSI represents but am having trouble with it and how it relates to my pool.

My pool is less than a year old and spent the end of the Summer and Fall getting things dialed in.

On 9/30/08 my numbers were:

CL - 10
Ph - 7.6
TA - 110
CH - 380
CYA - 45
Salt - 3500
Temp - 76
CSI - .01

Over the Winter my numbers have been creeping toward what I thought would be better and are now:

CL - 0 (this will be the subject of a different post)
Ph - 8.0
TA - 80
CH - 240
CYA - 80
Salt - 3750
Temp - 48
CSI - (-.33)

My biggest question is about the Ph. My normal target Ph when we were swimming was 7.5-7.6 and it occasionally would get as high as 7.7-7.8 before I had a chance to add acid. It has now settled at 7.9-8.0 and has been that was for quite some time. I know this is outside the suggested range but if I lower it to 7.6 my CSI will jump to -.7 which is too low. Should I lower the Ph and then raise the CH or just keep thing how they are until it starts to warm up?

Thanks,

Kevin

 

[JasonLion]

Mostly you don't need to worry about CSI much. As long as you are following the recommended levels fairly closely there isn't really any need to think about CSI. CSI is most useful when dealing with special cases, such as managing very high CH levels.

You will be just fine leaving everything till spring. Wait till you have the pump running and the water well mixed after opening, test the water then and adjust as needed at that point.

 

[cobra46]

Thanks Jason

Does your recommendation change if I don't close my pool. I live in California where we don't typically close pools. My pump runs everyday.

 

[JasonLion]

It mostly has to do with water temperature, not if your pool is open or closed. As long as the water is below 50 degrees, there is much less need to worry about the water balance (unless it is way out of line). If you are able to run the pump and the water is cold and things aren't way out of line then just add a little chlorine now and then and leave everything else till the water warms up.

As the water temperature goes down, the PH will tend to go up a little. The PH will come down again when the water warms up. The PH shift with temperature happens to more or less cancel out the CSI shift with temperature, so usually the best thing is to let the PH go up by 0.2 to 0.4 above normal (depending on how cold the water is).

 

[chem geek]

Kevin,

I can understand that your TA might drop over time as you add acid now and then from rising pH seen in most SWG pools, but your Calcium Hardness (CH) also dropped quite a bit from 380 to 240 and that shouldn't happen unless the water was getting diluted. However, your salt level has gone up, not down, during that same period. Did you, perchance, add salt? You have a cartridge filter so shouldn't be backwashing, so do you have any idea why your CH dropped? Have you had rains that overflowed the pool?

Richard

 

[cobra46]

Richard,

I intentionally reduced my TA by doing the waterfall acid thing, however, I can not explain the CH drop. It is actually much more dramatic than the test results I posted here. The day I got my TF Test Kit (9/4/08) I had a CH of 470 and it has been steadily dropping ever since.

I do have an autofill as well as an overflow drain. I have intended to turn the autofill off and do the bucket test to check for leaks but haven't got around to it. We are not that far apart so you know that we have not had a whole lot of rain this year.

The salt level went up because I added some.

I'm curious now about the mysterious CH drop. Maybe the tap water changed quite a bit as we went from summer to winter. I haven't checked it since my fill.

Regards,

Kevin

 

[chem geek]

The CH level of your tap water won't matter much unless it's quite high. If there is no dilution and only evaporation, then the CH would only rise from whatever is added from the tap water. So I suggest you check for a leak, as you mentioned.