I have a 25,000 gallon in ground concrete / plaster pool. It is an older pool (1998ish) but new to us - we just moved in a few months back. To prepare for the swim season I gave it a good shocking last night. Leslie's recommended 4lbs of Cal-Hypo Shock. I put that in last night at 7:00 PM and now 12 hours later it is cloudy as all heck. Water was crystal clear when I started.

I'm hoping that time in the sun today (Phoenix AZ 97 deg ambient / 78 deg water temp) will help to clarify but I'm still eager for your opinions and advice. Pool needs to be swim-able for Friday.

Welcome to TFP!

If the water is clear and the FC level is good there is no need to shock.

I suspect that you have trigged some calcium clouding. But it is impossible to know without a full set of water test results. Calcium clouding is usually fairly easy to clear up, though it depends somewhat on your levels.

Get a good test kit so you'll be able to test yourself.

Have you taken a sample to the pool store and had it tested? If so, post the results.

I suspect, like Jason does, that it's calcium clouding but a set of test results will tell us more.

Keep the pump running until it clears.

Why would you add calcium to your pool? Just shock with liquid chlorine!

If you dont have a test kit that tests for Calcium have them run one at the pool store. You'll most likely find your CH level is pretty high.

Honestly I dont know why they sell Cal-Hypo in the southwest. It's just asking for trouble.

I figured I owed you guys a follow up and kudos for the advice.

The water checked out perfect in spec. I meant to save and post the numbers but forgot. I think the print out is in the garage. If so I'll post up later.

Backwashing and a little clarifier did the trick.