Calcium Hardness rising?

[Steve-D]

My CH level has held steady all season but now the # is going up and I'm not sure why. The only change is I'm switching over to a new batch of reagents. Could that explain a swing of + 30 ppm? I've added no CH+ recently nor have I had to top off with fill water.

 

[mknauss]

30 ppm CH is not significant. Testing error.

 

[Steve-D]

Thx Marty.

It is probably the reagents then because I retested 3x yesterday and again today and results are higher than what I have been recording daily for the last several weeks. I saw the same on Saturday but didn't trust that result so I recorded the lower/historic #...I'll go back and change it.

So I assume if I was seeing 320ppm before but I'm seeing 350 now with no chemical additions or fills in between I should just go with the higher reading as per current testing?

 

[mknauss]

So I assume if I was seeing 320ppm before but I'm seeing 350 now with no chemical additions or fills in between I should just go with the higher reading as per current testing?

I would. Droplet size from one bottle to another can effect the result for that small amount.

 

[Steve-D]

For all my testing except Chlorine and CYA I'm using the Taylor K-2005 which calls for 44 ml water for the pH test, 25 ml for TA and CH...those reagents were newer coming from a test kit provided by the PB. I also use the 10 ml K-1766 salt test. I use the TF-100 10 ml DPD test for chlorine and the 30 ml (15 water/15 reagent) CYA . I would hope that the larger sample (25 ml vs 10 ml) translates to less opportunity for testing error given that the reagents for the CH test are the same in both kits. As I said, though, I switched reagent batches as I was running out of the supply from the K-2005 kit. All of the CH related reagents I'm using now are dated good through at least 12/2022.

 

[Krulligo]

How are you not getting evaporation. Do you use a pool cover or a lot of rain in your area?

 

[Steve-D]

@Krulligo - Yes, we use a solar cover cut to (mostly) fit. It is a PIA for one person to put on and take off so it stays on the pool unless we plan to use it. My wife and I work crazy hours and she has an exaggerated sense of what is "cold" so unless it gets uncomfortably warm outside the cover often stays on during the week unless we take a day off.

I haven't tracked actual rainfall but records for nearby Worcester MA report about 5 inches of rain Since early May when we first opened our pool. Between May and late June I added about 1 or 2 inches (600-700 gallons) of well water but the change in CH levels only showed up in the last week so it does not seem likely related to my fill (well) water. The only recent addition of water was about 0.75 inches of rain (250ish gallons) on Saturday afternoon and the first unexpected CH test result was from Saturday morning so again, I don't see an obvious correlation.

So I don't know what to think...I'm left with variations in test results due to a change in the reagents used.

 

[Steve-D]

For the record I tested my fill (well) water at the outside spigot/hose and these are the results:
FC 0
pH <7.0 (pale yellow significantly below the test kit color scale)
TA 70
CH 150
Salt 400

I added it as a note in PoolMath so its there with my logs for future reference