Why is my CH level gradually increasing?

[three4rd]

Hi,

I had replastering and fresh fill done last summer. Up until just the past few weeks, my CH level fluctuated within a range of 160-180, but since July 16 to the present, it has jumped up to 250 (210 on 8/10, 230 on 8/20, and now 250 today). I know these readings are all still within acceptable limits, but I'm wondering why the increase? The water level has been dropping with the lack of rainfall in our area and also probably attributable to later evening cooler temps, so I don't know if that has something to do with it. I am at the point where I soon have to start adding water. The other thing that is odd (which I alluded to in several other recent threads) is that I've suddenly developed what appears to be a calcium deposit issue on the grout. Should I be doing anything different in balancing the water? Or does a freshly filled newly plastered pool typically increase CH levels over time? My other current readings are:

TA - 100
pH - 8 (working on trying to keep that lower....this keeps going up for me also)

No chlorine....(biguanide)

Thanks for any thoughts,
Keith

 

[pabeader]

As water evaporates from your pool. The chem levels will appear to go up. Since all that is leaving is the water. Once you get it back up to normal level it should return to normal levels on chems. Unless your fill water is hard.

 

[Isaac-1]

You need to test your fill water to see how high the CH is, over time evaporation will concentrate your CH, and the higher the CH is in your fill water the faster this will happen.

 

[three4rd]

You need to test your fill water to see how high the CH is, over time evaporation will concentrate your CH, and the higher the CH is in your fill water the faster this will happen.

Thanks for the reply. My fill water appears to have virtually no CH based on my test kit results. Since we have a water softener, that would seem to make sense. So adding a few hundred gallons should most definitely lower the CH a bit!

 

[pabeader]

Wow! Usually the outside hose bibs are plumbed around the softener. At least, now you know.

 

[bdavis466]

Adding water with low CH will not decrease the calcium level in your water, it will gradually go up. The only way to lower CH is by draining water from the pool and replacing it with water that has a lower CH value (as in your case with the water softener) or by reverse osmosis systems designed for pools.

New plaster curing does have the potential to raise both the CH level (particularly if an acid startup was performed) and the pH.

With your numbers, I get a CSI of +0.57 (assuming 0 CYA, Borates,Salt) which explains why you are seeing scale. Lowering you pH and TA would help greatly to limit this occurance.