Hi I am a new pool owner and have been really grateful for the wealth of knowledge on this forum; I've learned a lot in a short period of time and the information here has already saved me a lot of time and money. Thanks!!!
Here's my issue: I am surprised at the delta between my TFP test kit data and that of the local pool supply company. They are using some kind of machine analyzer which is supposedly more accurate than the test kits (their view). I'll post mainly the Hardness and the Alkalinity data chronology because that is where I'm seeing the difference.
5/19 pool company analysis (last data from prior owner): Hardness 169 ppm Alkalinity 103 ppm. Adjustments by them are unknown.
6/26 TFP test kit (first reading after getting my kit): Hardness 250ppm Alkalinity 160
I added 10 lbs of calcium which brought my harness measurement to 400ppm on 7/3 and it has stayed in that range since.
I have added muriatic acid in half gallon increments followed by aeration to get the PH back up; total acid added has been 2.5 gallons. TFP results were showing slow progress on alkalinity: 7/3 140 ppm; 7/16 120ppm; 7/28 110 ppm. The last acid was added 8/1 using about 3/4 gallon.
7/28 TFP test: Hardness of 375 ppm.
8/4 My wife had a sample tested for correlation expecting to see corresponding data. Pool company tests: Hardness of 175 ppm and Alkalinity at 74 ppm.
In between this time and the below TFP tests I made no changes or additions, just ran the pump and salt water generator as normal. I was on a trip so wasn't able to test on the same timeframe:
8/21 TFP tests: PH 7.5; Alkalinity 130 ppm.
It's a big difference between the two results. Their hardness data doesn't make sense to me, given the calcium I added. But I'm even more puzzled by the alkalinity measurements. I can't seem to bring this down very effectively if I go by the TFP results; in this case the pool company result make more sense given the 2.5 gallons of acid I've added.
Thoughts? Any chemists out there?