Question about TFP CYA suggested level vs Pool Supply store

[Merccooper]

This will be my third year as a pool owner. The last two years I did chemical updates blindly based on what the pool store suggested. I had lots of problems (not all due to the chemical makeup) so this year I'm learning more before just following along. I've not yet picked up the suggested test kit (waiting for a trip to the US as the prices in Canada are stupid!). So below are the results the pool store provided me.

I have a question about the suggested CYA. the pool store suggests between 30 - 150 and TFP suggests between 60 - 80. This, at least to the newbe like me, appears to be a big discrepancy.
Not to question the wisdom of the folks behind TFP, but just trying to understand, why would there be such a large difference?

And the second question, should I now bring up the CYA to about 70 then bring FC to the target of 5?

FC: 2.46
TC: 2.79
CC: .33
PH: 7.7
TH: 216
TA (with stabilizer correction): 100
CYA: 25
Copper: 0
Iron: 0
Borate:0
Salt: 2800
Temp: ~75

 

[JasonLion]

We recommend different CYA levels depending on if you have a SWG or not. The pool store has one set of recommendations that are supposed to cover any pool.

When you have a SWG you want the CYA level between 70 and 80. This is a compromise between getting the longest possible cell life (higher CYA levels are better) and having some hope of defeating algae should you somehow get algae (lower CYA levels are better).

 

[jblizzle]

People in the pool industry to not seem to understand (or they ignore to better line their pockets) the relationship between the CYA and FC levels. As such, they say the CYA can be anything in a huge range, but do not correspondingly change the FC requirements.

There is plenty of science sited in many threads in the Deep End or Chemistry 201 that support our recommendations.

I would not suggest making any adjustments to CYA based on pool store testing ... they are REALLY bad at CYA especially. For example, one member kept being told their CYA was 40ppm ... with their test kit they found it was over 300ppm.