I'm a new home and pool owner as of December of 2016. My pool is 25k gallons, and yes, I get my water tested at Leslies. I still haven't found any reason to pay for a test kit when Leslies is 5 minutes away and does it for free. I've been able to maintain my pool and just fought, and I believe won, a battle with algae. After all was said and done, I finished raising alkalinity ( I know everything was done out of order ) by adding around 9 lbs of baking soda. Man! What a difference it made just visually. That baking soda makes my water look so much more blue! I'm going to get all my levels tested in the next day or so and add all my values into the pool calculator so I can add some borax. I need to raise my PH and I want some nice looking water, and the added benefits of borates to inhibit the algae growth. I know, I'm probably wrong on my though process and verbiage here, but I'm incredibly new to all this. My only real concern comes from my pump. It's a sand filter, although I'd have to double check on the model. I just know its a Hayward. We were told that the sand has all been replaced, but when we bought the house I found spare bags of all purpose sand in the yard. I'm concerned that the all purpose sand is what's in the filter, but all seems to be working fine. After a backwash, my filter's "baseline" PSI is 15psi. Should I go ahead and crack it open and take a look? I don't even know the difference between clean/dirty pool/all purpose sand.