Welcome aboard.
The thing to understand about the pool industry (stores, chemical manufacturers & service companies) is that their motive is driven by profit. A clean, clear and trouble free pool makes them no money. Pool services have one goal in mind - service as many pools in one work day as in-humanly as possible, spending no more than 15mins at a pool, and doing the least amount of cost-additive work possible. If they can walk through the fence gate, skim a few leaves off the surface, check the skimmer and the pump and do a quick check of pH and total chlorine, then that's more than enough in their opinion. Few service companies will do a comprehensive chemical check each and every time and the run-of-the-mill service guys probably can't even pronounce the word "CYA" let alone test for it or understand what it means. They simply are not hired to do that. Get in, make it look like you did something and get out...collect the service fee and go on to the next stop. Pool stores are even worse - if they have to have the guy or gal at the counter test your water, then they absolutely need you to leave the store with some overpriced chemical in hand. It doesn't matter if that's powdered shock your pool doesn't need, a bag of baking soda sold at 4X the price of the stuff you buy in the grocery store, or a magic potion that will fix whatever ails your pool water (according to their fancy computerized readout that has 5 different, conflicting recommendations). If you walk in, buy a bag of salt or a jug of liquid chlorine and walk out, there's not enough profit margin there to keep the lights on. As well, a green pool for them is nothing but an opportunity to sell you upwards of a thousand dollars worth of chemicals in nice $100-$200 installments with new recommendations each time you come back with a water sample ("add this, give it a day, grab a water sample and come back, then we'll do that all over again..."). If you're lucky and the pool clears up, then they've made you a happy and returning customer. If they fail, it's obviously because your pool water has too high total dissolved solids and the chemicals are no longer "working effectively" (whatever that means), you must drain the pool and start all over again....heads I win / tails you lose.
This is why TFP exists - to educate pool owners in how to take control of their own pools and care for their pools themselves using the least expensive means possible (if that's a concern for you) and to help pool owners diagnose equipment problems and determine the best solutions for fixing them. Once you take control of your pool, you stop needing a lot of the nonsense that's put out there to drain your wallet.
You'll do best to simply fire the service guy and stay out of the pool store. Ask any question you like...we're open all night....
