There are two ways you can remove calcium from your pool:

1. Drain 2/3 of the pool, and refill. With pool water CH=800 and fill water CH=110, you should end up with new pool water CH=340, which is acceptable. BUT, be careful to make sure your pool won't float! Dig a 3' deep hole next to the pool, and make SURE it does not fill with water. If it does, don't drain! Empty concrete pool WILL float on a lake OR in ground water!

2. Do lime softening, which involves raising the pH above 10.5 with soda ash, and precipitating the calcium as calcium carbonate, and then vacuuming it out. You'll need to be comfortable using the K2006, and be able to vacuum to waste, before you're ready to tackle this. This will remove more of your calcium, but will be more work. There's a bucket test you MUST do first, to make sure it will work, and that you have the right doses.

Meanwhile, keep your pH between 7.0 and 7.4.