Pool Store Water Tests and Calcium Hardness

ACastillo

Bronze Supporter
Apr 30, 2019
28
Pearland, Tx
I have a new pool that was filled Dec. 15th. Using my TF-100 test kit, I measured pre-fill water as having CH of 150, and immediately following fill up, I measured CH at 100. Trying to bring up my CH, I have added 45 lbs of calcium over the past month and a half, and using my TF-100 I'm sitting at about 250. Call me biased, but the water is beautiful and some of the clearest pool water I've ever seen!

At the recommendation of my pool builder (for plaster warranty), I have taken water to my local pool store for testing (3 times so far). I usually run a set of tests using my TF-100 that same day as a comparison and to see how far off their numbers are. Ph and free chlorine are usually pretty close, but the other numbers have enough variation that I think taking water to the pool store is a total waste. In particular, the pool store CH numbers consistently come in lower than mine, and during my most recent visit (2/1), they tested CH of 100 and recommended adding another 35 lbs of calcium chloride. With my TF-100 I had measured CH of 250 that same day, so adding 35lbs would raise my CH about 200, putting me at 450 CH. When the pool store employee mentioned that I needed to raise the CH, I explained that I had already added 45lbs of calcium chloride, to which he suggested that the recent rains likely caused a drop in my CH. Looking at the historical rainfall for the past month, I see that we only had 3.5" rain, so I find it hard to believe that it's dropped that far due to rainfall.

Here's a table showing my water tests (TF=TF-100 and PS=Pool Store) where you can see the appropriate bumps (TF numbers) in CH when calcium chloride was added.

Pre-Fill 11/20 TF12/13 TF12/15 TF*12/15 PS12/16 TF12/26 TF12/30 TF12/31 TF*12-31 PS2/1 TF*2/1 PS
FC
0.5​
1.5​
2​
2​
5​
5.5​
5.5​
3.5​
4​
2.5​
3​
CC
0.5​
0​
0​
0​
0​
0​
0​
0​
0​
0​
0​
TC
1​
1.5​
2​
2​
5​
5.5​
5.5​
3.5​
4​
2.5​
3​
pH
7.7​
7.2​
7.8​
7.8​
7.8​
8.2​
8​
7.5​
7.6​
7.8​
7.8​
CH
150​
100​
100​
100​
150​
175​
200​
225​
160​
250​
100​
TA
210​
190​
220​
100​
190​
170​
150​
140​
110​
100​
100​
CYA
10​
30​
30​
35​
45​
35​
35​
After adding 15 lbs CCAfter adding 10 lbs CCAfter adding 8 lbs CCAfter adding 7 lbs CCAfter adding 5 lbs CC

I'm a little torn because while it would be nice to have a third party validate my testing results (mainly for warranty purposes), seeing the discrepancies over each of my 3 visits wouldn't seem to give me much support if there ever was an issue. I suppose I could take a water sample to another but I don't think I'd have much faith in any pool store testing.

Does anyone really go through the trouble of taking water to a pool store for a second opinion? As of a few weeks ago, I paid for Pool Math, so all my testing and chem additions are documented in the app. Has anyone ever used the Pool Math logs for a warranty claim?
 

Katodude

Silver Supporter
Aug 22, 2017
572
West Palm Beach/Florida
The pool store is wrong, plain and simple. You have a top of the line testing kit and you are more concerned about your pool than anyone else so that means you will pay the most attention to testing it right. The only thing I would change is get a SpeedStir, it will make your testing easier and more accurate. Especially for the TA and CH parts.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I agree with Kato. The pool store will never give you the accuracy you deserve. Here's the bad part - I'm not aware of any manufacturer who will honor owner/user home testing. I went through that wish our FG pool. It's a fallacy of the system that the pool industry demands owners go to a pool store that in many cases provides incorrect, unreliable testing either due to inferior lighting, skills, or seasonal training. The pool stores also employ pool industry chemical standards that do not account for all scenarios of pools (i.e. SWG, pool type, weather, etc). But those are the rules pool owners are asked to follow. I doubt the rains had any impact on the CH unless you actually exchanged water. CH doesn't dilute. So if you chose to get pool store tests simply to have their numbers on file for your warranty, that's fine. But I would still reply on your TF-100 tests for daily maintenance.

When you look at your pool store tests, you can see their TA was about 100 off from yours as well in Dec. There's no way that number should be so far off. Typically, it's common to see a TF-100 (or Taylor K-2006) owner see their CYA test much different than the pool store. TA and pH are generally straight-forward and somewhat close. CH can vary as well, but about 100 ppm off between the two is odd. Still, if you are following the TF-100 directions and the Extended Test Kit Directions Archives - Trouble Free Pool with no issues, I place accuracy in your testing. If you have any doubts about the testing, make sure to ask. For what it's worth, I use the 10 ML water sample size for my CH testing, and make sure to add drops (R-0013) until the sample turns a light baby blue. Maybe the store isn't taking the sample all the way to baby blue? Hard to know because they usually fly through the process.

If you wish to go to a 2nd place just out of curiosity, you certain;y can. Keep in mind it may not validate your concerns based on their accuracy, skills, training, and lighting. You can also test your PS testing by having a sample tested today, then again tomorrow. There's no way CH, CYA or TA will change overnight. That's how I "calibrate" local pool store tests. If you don't have a speedstir, I would get one. I can't live without one, that's how great they are. But at this point, I wouldn't add anymore calcium. Get a speedstir and compare all the testing a bit more to be sure.
 

ncbart

Member
Aug 5, 2019
14
TX
I have a new pool that was filled Dec. 15th. Using my TF-100 test kit, I measured pre-fill water as having CH of 150, and immediately following fill up, I measured CH at 100. Trying to bring up my CH, I have added 45 lbs of calcium over the past month and a half, and using my TF-100 I'm sitting at about 250. Call me biased, but the water is beautiful and some of the clearest pool water I've ever seen!

At the recommendation of my pool builder (for plaster warranty), I have taken water to my local pool store for testing (3 times so far). I usually run a set of tests using my TF-100 that same day as a comparison and to see how far off their numbers are. Ph and free chlorine are usually pretty close, but the other numbers have enough variation that I think taking water to the pool store is a total waste. In particular, the pool store CH numbers consistently come in lower than mine, and during my most recent visit (2/1), they tested CH of 100 and recommended adding another 35 lbs of calcium chloride. With my TF-100 I had measured CH of 250 that same day, so adding 35lbs would raise my CH about 200, putting me at 450 CH. When the pool store employee mentioned that I needed to raise the CH, I explained that I had already added 45lbs of calcium chloride, to which he suggested that the recent rains likely caused a drop in my CH. Looking at the historical rainfall for the past month, I see that we only had 3.5" rain, so I find it hard to believe that it's dropped that far due to rainfall.

Here's a table showing my water tests (TF=TF-100 and PS=Pool Store) where you can see the appropriate bumps (TF numbers) in CH when calcium chloride was added.

Pre-Fill 11/20 TF12/13 TF12/15 TF*12/15 PS12/16 TF12/26 TF12/30 TF12/31 TF*12-31 PS2/1 TF*2/1 PS
FC
0.5​
1.5​
2​
2​
5​
5.5​
5.5​
3.5​
4​
2.5​
3​
CC
0.5​
0​
0​
0​
0​
0​
0​
0​
0​
0​
0​
TC
1​
1.5​
2​
2​
5​
5.5​
5.5​
3.5​
4​
2.5​
3​
pH
7.7​
7.2​
7.8​
7.8​
7.8​
8.2​
8​
7.5​
7.6​
7.8​
7.8​
CH
150​
100​
100​
100​
150​
175​
200​
225​
160​
250​
100​
TA
210​
190​
220​
100​
190​
170​
150​
140​
110​
100​
100​
CYA
10​
30​
30​
35​
45​
35​
35​
After adding 15 lbs CCAfter adding 10 lbs CCAfter adding 8 lbs CCAfter adding 7 lbs CCAfter adding 5 lbs CC
I'm a little torn because while it would be nice to have a third party validate my testing results (mainly for warranty purposes), seeing the discrepancies over each of my 3 visits wouldn't seem to give me much support if there ever was an issue. I suppose I could take a water sample to another but I don't think I'd have much faith in any pool store testing.


Does anyone really go through the trouble of taking water to a pool store for a second opinion? As of a few weeks ago, I paid for Pool Math, so all my testing and chem additions are documented in the app. Has anyone ever used the Pool Math logs for a warranty claim?
Just as a side note, my CH decreased from 600 to 350 from rain from Tropical Storm Imelda back in September. We got close to 30 inches of rain in a matter of 5 hours. I say this because while it's possible your CH could decrease from rainfall, I think 3.5" is an insignificant rainfall if you use my scenario as a comparison.
 

SyncLock

Member
Aug 30, 2019
7
Gulf Coast, AL
I've had the same trouble trying to find a pool store that I agree with on water testing. I was also told to have a monthly test at a pool store for warranty. My goal was to have a perfect official test each month but that has been a bigger challenge than I expected, in fact its become the biggest headache of my pool and in my opinion the hardest part of TFP. After about the 5th store I finally found one that produced results that match my own(for now). I had the most trouble with calcium and salt levels and would get huge variations from the pool stores. Ironically the pool stores that charged for the test were the worst results. My wife was not enthused when pinch-a-penny rang a bell for me having a perfect pool, she said I'm already obsessed and didn't need the encouragement. :ROFLMAO: But I haven't heard any complaints from her about the pool water so I'll keep it up! Honestly I was so happy to finally get that validation, I had started to believe my own testing was wrong and was considering a pool service even though my water was perfect the entire time.
 

ACastillo

Bronze Supporter
Apr 30, 2019
28
Pearland, Tx
I appreciate everyone's feedback. I definitely put minimal value in the pool store testing, each time the guy doing the testing was either talking to me or talking to someone else, so his full attention was not on the testing.

Texas Splash, thanks for the additional reading materials on the extended testing directions. After reading, it seems that I'm following the testing steps correctly, not to mention that hopefully my 18 years of molecular biology and cancer research give a little validity to my analytical techniques :p. Needless to say, I'm fairly confident in the TF-100 results (note- all the results were using a speed stir, I've updated my signature).

In my last visit, the pool store employee did mention they were moving to a fully automated testing platform. I guess it removes some of the user error and variability, but it may raise other issues.

I just think that its crazy that some people rely solely on pool store testing, which I know some people who do from talking to others who have pools. I'm sure this has been a topic of discussion, so I won't go down that path. For now, I may just play along and see if the new system improves anything.

Thanks for the input everyone!
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
32,898
Sebring, Florida
Unless you experience overflow during a rainstorm, the rain has no permanent effect whatsoever on CH.

Rain (again, unless there is an overflow) doesn't affect CYA either.
 

sktn77a

Gold Supporter
May 16, 2010
1,487
Chapel Hill, NC
In my last visit, the pool store employee did mention they were moving to a fully automated testing platform. I guess it removes some of the user error and variability, but it may raise other issues.
Unfortunately, most of the "fully automated" systems now simply use a test strip which is read by a "black box". Quick and dirty! I would rely on these even less than the old pool store chemical tests.