Rising pool pH with SWCG

[spibill]

My pool is has an SWCG, and I am having a problem with the pH constantly rising. What can I do?
Muriatic acid is relatively cheap, and once you learn to handle it, not hard to use. So it's not really that much of a problem. But, you can often reduce the pH rise by the following steps:

• Increase the CYA level to 70 ppm or higher, which will reduce SWCG on-time.
• Decrease the TA to 70ppm or lower. (Increase the calcium to compensate on concrete pools).
• Add 50 ppm borates (borax) to help stabilize the pH. (This will require a one-time pH adjustment, since the borax is basic, and causes a pH rise itself.)

(from http://www.poolsolutions.com/gd/swim...ators-faq.html )

I have this problem. How do I determine how much borax I need for a 5,000 gal pool/hot tub?