Fill water has low CH, but pool water is high CH?

[jamyers]

Using my TF-100 kit w/ speedstir, today I tested not only the pool, but also the water coming out of the well I use to fill/replenish, and here are the results:

Well
FC = 0
CYA = 0
pH = 7.2
TA = 440-450
CH = 350

Pool
FC = 11.5
CC = 0
CYA = 60
pH = 7.2
TA = 120
CH = 525

No real surprises there for me, except the CH - why/how is the water going from a CH of 350 to 525, and should I care? It's a plaster pool built in '85, never been painted or re-plastered, and has no cracks, only surface etching from where MA was previously added in slugs (according to local pool store)

 

[jjslinger]

Someone who knows more than me will surely reply soon, but here is one explanation. As water evaporates, the calcium stays in the pool; then more fill water comes in with more calcium. Then more water evaporates. Etc. Eventually, the CH drifts up.

Don

 

[jamyers]

Someone who knows more than me will surely reply soon, but here is one explanation. As water evaporates, the calcium stays in the pool; then more fill water comes in with more calcium. Then more water evaporates. Etc. Eventually, the CH drifts up.

Don

That may well be the case, since this pool hasn't been drained since Aug '07 (now why didn't I think of that???)

Anybody see a reason to be concerned? CSI as per the pool calculator is -0.01, the target? is -0.22.

 

[jjslinger]

That may well be the case, since this pool hasn't been drained since Aug '07 (now why didn't I think of that???)

Anybody see a reason to be concerned? CSI as per the pool calculator is -0.01, the target? is -0.22.

More knowledgeable people will respond, but I think the CSI target is 0; +/-0.3 is considered "okay"; beyond that, the pool calculator may start giving some warning comments. I like to keep my CSI as close to 0 as possible.

Don