Regarding calcium and alkalinity -- did you watch the Taylor interferences videos? How did those results compare to yours?

Regarding high CYA + high chlorine (HiC2) -- we had a pro & con discussion among the moderators and the PF Team members, and the downsides most people were concerned with were

1. The need to use EXTREMELY high chlorine levels to clear mustard or black algae, possibly over 50 ppm. These levels can take a very long time (3+ weeks) to drop.

2. Difficulties with pH testing (see the Taylor pH interferences video -- stickied in the Testing section)

Janet (Aylad) runs a near HiC2 pool (CYA levels almost identical to yours) with few problems, but otherwise, I was the only one completely comfortable with the HiC2 approach. However, since that debate, we've done some testing that suggest the pH test IS accurate with high chlorine levels, IF you read the test within 5 - 10 seconds. If you let it sit, before reading it, you'll get bogus results.

For what it's worth, I've been running a large (200,000 gallon) commercial pool at CYA ~90 and FC ranging from 5 - 25 ppm (typically 12 - 20 ppm) this season, with ZERO complaints. No one has noticed, except the health inspector, who commented that the chlorine was "a little high - 10 ppm" (it was really about 20 ppm that day!). I've repeatedly asked the lifeguards if anyone has the pool being irritating, and none of them have.

This pool has always been extremely prone to mustard algae, possibly because it's right on the Tennessee River, and I've noticed the algae will try to return with levels get below FC=10ppm.

Regarding the algae problem, my preference is to take the chlorine to 30 ppm, and hold it there. If that doesn't solve the problem, the next step is to add small amounts of sodium bromide, creating a small unstabilized bromine residual. Without the presence of DMH (dimethyl hydantoin, used in formulating bromine tabs), bromide is converted to bromate (non-regeneratable) in a matter of days.

So . . . personally, I would NOT recommend trying to lower your CYA level. But, not all my moderators and Support Team members agree. (Yet. )

I did want to ask a question about your bucket test: when you added the soda ash, no clouding occurred? No sediment formed on the bottom? Can you try again, with these guidelines: http://www.poolforum.com/pf2/showthread.php?16992 ?