Any connection between SWG and calcium deposits?

[waterbear]

My pool has been very quick to change ph (upwards). I've always attributed that to the SWG. I usually need to add about a pint a day, and have needed to do so since startup two years ago. Now in the summer, when the SWG is turned up because of more chlorine eaten up by sun, I have to add more muriatic.

Short and long of it is highly unusual for me to have a ph of anything other than between 7.2 and 7.5.

Try dropping your total alkalinity to about 70 ppm, and when you add acid shoot for a pH of 7.6. You might find that this gives a a better pH stability with the SWG operating. Also, I have had excellent results by adding 50 ppm borates to the water. You can do this with such products as Proteam's Supreme or Bioguard's Optimizer but if you are cheap like me you will do it with 20 mule team Borax! See this thread:
http://www.poolforum.com/pf2/showthread.php?t=4712

Aslo, what type of SWG do you have? You seem to be running your CYA on the low side and this can also contribute to pH instability by causing the cell to work more than it really needs to. Most manufacuters recommed a CYA of 60-80 ppm (one I know of recommends 80-100 ppm and one I know of recommends 50-80ppm ) and there has been an excellent discussion on this board as to why this is most likely a good idea!
http://www.poolforum.com/pf2/showthread.php?t=4495
I test a lot of pool water every day i'm at work and have a lot of customers with SWGs besides having one myself. I see fewer problems in the pools that have the CYA in the manufactuers recommended range than in the ones that try to run it lower. This emperical evidence is enough to convince me that follwing the manufacturer's recommendation in this area is a good idea! Ditto on running the TA on the low side. I have found that when the TA is dropped to around 70 ppm the acid demend tends to go down. Chemgeek has given an excellent explanation of this in another thread
http://www.poolforum.com/pf2/showthread.php?t=5379

Hope this helps.