Draining and refilling Pool

[Nixid]

I understand that I need to test the water before adding chemicals to it.
I would like to know if anyone has a good estimate of what I will need to balance out my 40k gallon pool so I can go shopping ahead of time.

 

[Bama Rambler]

If you'll take your test kit and run a full set of tests on your fill water you'll have a pretty good idea of what you may need once you fill it.
Chlorine of course, but the rest depends on the fill water.

 

[jblizzle]

Certainly will need chlorine and stabilizer (CYA). But any adjustments to the pH, TA, or CH depend on your fill water as Dave stated.