Ok cya levels have gotten out of control..( I know I know trouble free pool) but the time has come as I need to drawing at least half or more and refill.
So this week I'm off and need to get it done however we just had 1.5 inches dumped yesterday and I'm worried about my ingroud concrete possible floating up. Should I be worried if I'm draining and refilling immediately? Or should I wait for a drier time to do this?

Decided to to 10 inches at a time

Just drained 10 and now refilling
Will repeat as necessary to get my cya down to 50-60 range hopefully after 2-4 10 inch runs

If that was my pool after floating it I'd just take it out
It's a 1980 pool which causes more headaches than anything

Rustys-Beef-o-Reeno said:

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Decided to to 10 inches at a time

Just drained 10 and now refilling
Will repeat as necessary to get my cya down to 50-60 range hopefully after 2-4 10 inch runs

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My guess is that it takes alot more than 2-4 times if you do that.

I'd just wait and do it all at once. Otherwise you're always going to be draining some of the new water that you just put in and it will take forever to bring down the cya.

Why not just a put a hose in it and let it run?

Case 1:
Assumptions
1. CYA = 100
2. Desire CYA = 50

Action
Drain 50% of pool and refill.

Case 2:
Assumptions
1. Same as above
2. Average depth 4 ft
3. Drain 10"and refill

Action
1. Drain 20% and refill. CYA drops from 100 to 80
2. Drain 20% and refill. CYA drops to 64
3. Drain 20% and refill. CYA drops to 51 (close enough)

In this case you have put 60% of the water in fresh as you loose some fresh water each cycle. Is this significantly different than putting a hose in and letting it run? Draining 1% at a time seems to increase total change to be 70% refill.