Thanks for your advice.

The guys who installed the coping already tried to get those marks out -- they did a very light acid wash -- and nothing happened - you see them as they were.

On a separate test piece I tried TSP and that did not work - stained the piece even worse.

So you suggest:

1. Grout the coping
2. Put in the expansion joint between the coping and the deck pavers (which are in sand)
3. Use the pool for a season - even though the coping shows the alkalie marks as well after they are wet.
4. At the end of the season, then do a light acid wash again.

Is that about it?

Again, thanks for posting and for your advice.