I'm a bit stumped on this one and was hoping for some help. We replastered the pool and filled it about 40 days ago (just bought the house and immediately did a replaster). At that point, I added enough stabilizer to get the CYA up to 40 (per PoolMath). Two weeks later, CYA measured in at 20. Again, I added enough stabilizer to get it up to 35 or so. A week later, it measured at about 25. I added enough stabilizer to get it up to 35 again. Today it measured at a bit over 20, maybe closer to 25.
What on earth could be causing my CYA to continue dropping? We do have an automatic filler on the pool, but I rarely if ever hear it on, so I can't imagine it's auto-filling and draining the water constantly. Also had one big rainstorm which might explain one of the drops, but not all three. (Also, before anyone says I should have been targeting a CYA of 50 and not 35, I agree - I'm going to be out of town for 7 days in a couple of weeks so I was keeping the CYA lower so that I could use some pucks then and end up at a CYA I like).
Any thoughts what might be going on? I thought CYA could only go down if water were rained and refilled. Thanks for any help.