Increasing Calcium Level

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I bought a house a year ago and it had many issues when I purchased it. The ongoing problems that I have had have to do with high CYA and Calcium levels. I have switched to SWG so that no more CYA is being added and I have been draining and refilling as possible in order to get the levels down. Here in Texas we cannot afford to drain 1/2 a pool due to the cost of water. (Especially since the water rates increase with usage)

So my solution has been to drain 3-4 inches a month and then refill what I can each month. In addidition I have closed my overflow and run the pool level at the bottom of the skimmer to allow the free rain water to dilute the pool. This has been successful for the CYA which was puching 200 a year ago and is now down to abou 115 or 120. (it's an estimate when over 100 if you are using a taylor kit, but it noticable the difference and I'm getting close to the 100 mark)

However, the Calcium level just keeps increasing even as I dilute the water and can see results with the CYA. I have tested my tap water that I refill with and the calcium level is about 110, so I should be lowering the level with the tap water. So my question is where can calcium come from other then if you add it?

My current levels are as follow:

FC 6.0

CC 0.0

TC 6.0

PH 7.2 - 7.8 weekly with on Gal of acid to adjust from 7.8 - 7.2

TA 120

CH 460 (was at 400 about a month ago)

CYA 115

TDS 4200

Salt 3100

The only chemicals I add are 1 Gal of acid weekly. Chlorine (unstabilized bleach) monthly to shock. and some salt occasionally to keep the salt level at 3100-3200 as I dilute. The pool is white plaster with tile at the water line and brick coping. There is also a spa that has a layered brick waterfall flowing to the pool. Could there be some sort of chemical reaction that is causing the calcium to increase? In the past I had calcium deposits in the waterfall which would imply just the opposite that the brick caused the calcium to calcify rather than that it would increase the calcium.

Any thoughts on the source would be helpful since I really want to get this calcium level down.