This must be a fiberglass pool.

Nope, plaster.

Still I can't understand what the temperature has to do with it. Where are you and what was the reason
for the 75 degree limit?

I'm in Phoenix, Arizona. The problem is that the plaster can crack and
come off in large chunks.

I've spent a good part of my life down in them holes and have never heard that one before.

Pretty common knowledge, apparently. All the pool companies in this
area were well aware of it and I found several references to it on the
Web. Significantly, most of the references came from pool companies in
the desert. I guess it's a non-issue in most places.

All I know is that when it starts getting near 120 degrees you won't find me in one past
about noon. I just love that one sales baby asking me if I'm going to
lunch when I'm leaving for the day. I get up around 3am and go as fast
as I can non stop till I about forget my name from heat stroke and I'm
outta there.

Only because you're smart. Similar schedules are the norm for
construction crews around here in the summer. The sleepyheads start at
6 a.m. and a lot of them start earlier.

--RC

"Sometimes history doesn't repeat itself. It just yells
'can't you remember anything I've told you?' and lets
fly with a club.
-- John W. Cambell Jr.

Must be a Vegas thing cause they want it done anyhow after you warn
them about the plaster checking problem. I've done a number of them
where I'll drop off the pump in the afternoon, fix the pool first
thing in the morning, and set up a floating sprinkler to fill it back
up. Then the customer calls when its full, go over and start the pool
up , and grab the $ and sprinkler. What gets me it people crying cause
of the cost , hey that's 4 trips (I want to see it first) without any
problems. That's only done with really anal customers or the pool is
under 3 years old. Otherwise it checks or doesn't, not my problem ,
and if I tried to make it such I'd be told to do it anyway.

Usually, pool people are so busy in the summer time that we'll come up
with anything to put you off till winter. Or at least I do. Yeah, yeah
, that's the ticket , the plaster will check. )

You could have shocked the crap out of it. Just have to be a little
careful that you don't get the water into that irreversible condition
or etch the copper heat exchanger and other copper plumbing and have
your plaster turn blue like the OP's pictures.

Pebble tech is 10 times better. I never did like that sterile white
plaster. I'd have a blackish pebble tech or all mosaic theme tiled
pool.

Oh yeah, those nazi police probably take addresses from the air for
ya'll west Nile virus breeders. LOL , just kidding.