Some pieces of Oklahoma flagstone will flake because that is the nature of that type of stone. There are pieces on the front of our house that are flaking and have never been hit with ANY water other than rain. Sealing the flagstone helps on a salt water pool, but it doesn't completely prevent flaking (at least according to my experience with our pool).

It is common to have flaking on Oklahoma Wister, but perfectly normal as natural stone does that.

We had some flaking and sand in the pool from our Oaklahoma flagstone coping.

I sealed it once, and it helped. 2nd time I coated it really well. Very little sand in the pool now, flaking has all but stopped.

Will renew each year as needed from here on out, only took a couple of hours to do.

Thanks for the responses. We went ahead and used the OK flagstone. It turned out really good. I need to figure out how to post a few pictures.

Suzee, did you seal the flagstone coping? We are getting ready to remodel our pool and I also chose Oklahoma flagstone.

We used Oklahoma flagstone coping on our pool we built in late summer 2008. We were not encouraged to seal it by the pool builder since we have a chlorine pool. However, the well water in our town has a high sodium content, so much so that water sprinklers that routinely hit an area, leaves white build up. Over time, it builds up into miniature stalagmites. But I digress.
Our Oklahoma flagstone is spalling very prominently in places. It is pronounced in the deep end where kids grasp the coping

Has erosion gullies

and when wet, becomes very sandy and easily etched. It is etched deeply in some areas, where the polaris pool cleaner wheel gouged a track when it was taken out of the pool.

We will be cleaning and sealing it but if I had to do over, I would not go this route again.