I went to the Pool Store (the one that rhymes with Nestle's) for the first 4 weeks of pool ownership. I had zero previous knowledge about pools. I needed to know if I had any emergencies to react to, and I figured I'd learn a few things and possibly pay a bit more for chemicals in exchange. I thought I'd share exactly how the process worked for me. I got my TFT-100 a few days ago and I've learned so much since then.
1. Chlorine. Pool Store FC max result was showing 6. TFT-100 showed 12.5. [Edited based on my previous mistake caught by Schadenfreude post below]
Therefore Pool Store underprescribed dosage of MA required to get pool down to 3-5 range. Pool store alsodidn't advise me to reduce SWG % [which was likely driving consistently higher pH levels of 8+]. Was this to just keep me on a relentless routine of adding more MA? Were they secretly hoping for an earlier-than-necessary Salt Cell replacement sale?
However, Pool Store was happy to sell me Fresh N Clear and Chlor Brite, as "most owners" need additional chlorine added on top of SWG generation. Don't know if this was accidental (only reading up to 6, not the actual 12 via TFT kit) or intentional, but I was WAY overproducing chlorine already, yet they sold me additional chlorine products I won't be needing unless there's a crisis/failure.
2. Calcium Hardness. Pool Store CH reading was showing 190, so they sold me 15 lbs of Hardness Plus, indicating I needed to add 11.4 lbs of it. After adding the Hardness Plus, the Pool Store reading was up to 310, considered "OK". TFT-100 test later showed that CH was closer to 525, so I was oversold product and overapplied product.
Pool Store has no testing or reporting of CSI. Now, thanks to this forum, I know that unless I make changes, I'm at risk of long term plaster damage. I must now work to get CH back down to 350-400 range.
3. Phosphates. I have been using Perfect Weekly since my pool's former owner recommended it - it seemed the Pool Store guy was disappointed that Phosphates kept coming up 0 - was he secretly hoping to sell me something additional?
4. Testing Interval. I wonder if the Pool Store recommended "free water testing" interval of 2 weeks is also part of the carefully crafted business strategy? It's long enough, and combined with bad readings, that could lead a pool owner into a "manufactured crisis"? This leads to an immediate panic, which means SPEND immediately: no time to shop around, you need to buy chemicals and add them ASAP! And the Pool Store looks like "The Savior" because they helped you work through your issues.
Then 2 weeks later, you may discover that you have over-corrected or under-corrected, then leading to even more chemical purchases to deal with the next situation or imbalance.
Overall. A combination of infrequent, inaccurate, inconsistent, and incomplete water test readings, plus possibly mis-diagnosis or oversimplification led to these mistakes. Since then, I have also learned how to obtain chemicals from less costly sources, which will be a financial help.
So glad I started learning early about TFPC methods in the first month, with more to learn ahead!
PS-Testing inconsistency plagued other readings from the Pool Store until I got my TFT-100: TA bounced around from 90 to 120, but my TFT tests are a consistent 110. CYA bounced around from 60 to 90 without adding any conditioner, yet my TFT tests are a consistent 80. Both of those fell into the "OK" range and did not result in extra chemical purchases, but those are pretty wide ranges within a week.