CH jumped from 275 to 400-425?

[Ronald U.]

I typically run CH 275 - 300. I didn't add any calcium intentionally (no Ca shock, Ca chloride). Today I was doing my weekly chemistries and find 400 and 425. What can cause such a jump? Thank you.
Here are my other latest numbers:
pH 7.7
FC 6.0
CC 0.5
TA 80
Salt 1800 ( about 10 days ago)
CYA </= 40 (8 days ago; too cloudy just now to run test)
Borate 40

 

[Mr Bruce]

What's your tap water? Have you had to replace water lost from evaporation or splash-out?

 

[ping]

How much time has passed between the 300 to 400 readings?

What does the fill water CH test at?

The CH level in my pool increases about a 100 each summer due to evaporation and refill.

 

[duraleigh]

Since your weekly testing indicates a jump of 125 in one week, about the only logical thing that makes sense is a testing error.

 

[Ronald U.]

Fill water CH 200. / The only thing different in this week's testing is a new bottle of R-0012. Don't know how old this bottle is but I only started TFP and bought a TFT kit in May 2015.

 

[duraleigh]

To my knowledge, "newness" has no affect on the CH test.

 

[Isaac-1]

Was your old bottle of CH reagent ever exposed to temperature extremes? You should store your test kit indoors in a cool dark place

 

[Ronald U.]

Working kit is stored indoors but by a window. Spare chemicals indoors in a drawer.

 

[Ronald U.]

One week later my pool has increased CH again, to 425 - 450 (2 tests). I'm still scratching my head...

 

[ping]

How much fill water are you needing to add each week?

Are you using a SpeedStir?

A range of 400-425 and 425-450 is well within testing errors and shouldn't be cause for alarm. A CH of 450 is very manageable, hopefully some rains this winter will dilute it some.

 

[Ronald U.]

No fill water was used in the week CH went up from 400 - 425 to 425 - 450. Just a bit of rain kept water levels up.

 

[duraleigh]

CH is probably the most stable of everything we test. It never leaves a pool and generally increases slowly, depending on amount of fill water.

Since your testing seems dependable and repeatable, that can only mean CH is being introduced into your pool. What the source is I certainly can't tell.

If you can't get it figured out soon, I would suggest you drain about a foot of water and replace it with your 200 CH fill water. That may be a permanent exercise unless you find the source.

 

[Ronald U.]

I occasionally creep into the "potential" problem negative CSI (< -0.3 but > -0.6). I assumed this still means I am not leaching calcium from plaster walls. Extremely rare I go into < -0.6, and then for less than 24 hours. / I will ask my wife if she's applied anything in the surrounding vegetation. The case of the mysterious calcium.