My responses in bold in your quoted post below.
Quote Originally Posted by jereece View Post
I really appreciate the education. I when ahead and ran a complete set of analysis and I have a question about the pH. I used a Taylor K-2500 kit.
I think you mean the K-2005 test kit. This uses a DPD chlorine test which only lets you measure chlorine up to 5 ppm. A more accurate test is found in the K-2006 test kit and is called a FAS-DPD test. It can measure up to 50 ppm and has a resolution of 0.2 ppm or 0.5 ppm depending on sample size and it accurately measures both Free Chlorine (FC) and Combined Chlorine (CC). You can just get the FAS-DPD test separately as the K-1515-A from Taylor here.

Free Cl2 = 5
pH = ~ 7.1 (Taylor) 7.37 (Laboratory Probe)
CYA = 30
TA = 40
CA = 20

I was a little surprised that TA was 40. I thought it would be lower.
Fill water usually has some TA in it as well as some Calcium Hardness (CH). The TA of 40 is not at all unusual, though the CH of 20 does mean the water is "slightly hard" since the total hardness is probably around 30 ppm. Soft water is < 17 ppm total hardness, slightly hard is 17-60, moderately hard is 60-120, hard is 120-180 and very hard is > 180.

As for my pH, my Taylor kit shows a color somewhere between 7.0 and 7.2. However I took a sample into work and had one of our chemistry tech run the pH using a calibrated probe. They got 7.37. I suppose I need to raise the pH a little as my primary concern is corrosion of the walls should I have a leak. As I said in my original post, I replaced the liner this spring and to my surprise found a good bit of surface rust on the walls. I removed the rust, treated it with rust converter, then painted the entire wall with aluminum Rustolium paint and then coated the lower 1/3rd (where most of the rust was) with rubberized undercoating.
The pH will change over time, usually rising, if your sample got shaken or aerated on the way to the lab. The outgassing of carbon dioxide causes the pH to rise. To verify the accuracy of the Taylor test, you should take the kit with you to the lab and test them side by side on the same sample water. If that is what you did, then one or both tests are a bit inaccurate.

I originally thought my pH would come up naturally using bleach, but with such low alkalinity I may need to bring it up another way.
Bleach and chlorinating liquid initially make the pH go up upon addition, but the usage of chlorine is an acidic process that balances the initial pH rise so the net result is no change in pH (pretty much). Usually, a pool rises in pH due to the over-carbonation. So what you are seeing is normal.

Questions

1) Should I go ahead and manually bring the pH up to some higher value?
Yes you should. If you want to do so without changing the TA, then you can aerate, though at your low TA level this might not be very successful. You can add 20 Mule Team Borax to raise the pH. Don't forget that it will take much less acid or base to move the pH at your TA of 40.

If I assume your 27' is the above-ground pool diameter and that it has a 48" (4') depth, then that's 3.141*(27/2)^2 * 4 = 2290 cubic feet which is 17,130 gallons so let's call it 17,000 gallons. To raise the pH from 7.1 to 7.5 would take 39 ounces weight (about 4-1/2 cups) of Borax and the TA would only rise by 4.5 ppm. To raise the pH from 7.37 to 7.5 would take only 9.5 ounces weight (about 1 cup) of Borax.

2) If so, what pH should I target considering my low alkalinity?
You use the same pH target at the lower TA, namely 7.5 so that it is easiest on the eyes while not being acidic for the vinyl.

3) What should I use to get the pH up?
Either aeration or 20 Mule Team Borax as indicated above.

Again, I really appreciate the help.
That's what we're here for! And you are a great experimenter and help confirm theories that are doubted by some (mostly in the pool industry).

Jim