TA reduction going wrong ??

I will give you some back ground on my pool and setup before getting to my problem. I live in N. central Texas near Waco. I have been using the BBB method since 2010. I own a Doughboy above ground '14 X 32' 12,500 gallon pool. My equipment consists of 0ne Doughboy 19" sand filter and a aftermarket 3/4 HP pump. I also have installed a Circupool RJ-60 SWCG system rated for 20K pool ( Not turned on yet).
For water testing I am using a Taylor K-2005c and FAS-DPD K-1515-A plus a LaMotte Borate test strip kit. I decided to cover my pool last November for the first time and did not uncover it until July 15th ( mostly due to installation problems with my SWCG system). When I put it to bed last fall the water had 50 ppm borates, CYA 50 ppm, TA 300 ppm, CH150 ppm and I had increased the Free Chlorine level to 10 ppm. When uncovering my pool I found completely clear water, no signs of algae. Other than a minor amount of dirt I had scaly brownish deposits that look like sand on the bottom of my liner that just continued up the sides about 6 inches. Almost all the deposits were around the edge in a 2 foot wide band( and most are still there). My chemistry numbers were Borates 50ppm, CYA 0 ppm and TA 250 ppm and CH 70 ppm( later learned after I added to my pool it was unnecessary in vinyl pools) .
In prep to start up my SWCG system I have added 400 pounds of salt as MFG's instructions. Since adding salt the PH has pegged out my test kit to the upper limits. Since my CYA had disappeared over the period it was covered I have been using some HTH Calcium Hypochlorite tab I had left over when I went to BBB in 2010. Now after using about 8 pounds of the HTH product my CYA has increased back up to 30 ppm. The SWGC MFG suggested having the water numbers balanced and in good condition before starting the SWCG system.
After referring to my Taylor K-2005c instruction booklet, I had started to try and lower my TA to 70 ppm. When I did the math to lower my TA from 250 ppm I needed to slug 3.5 gallons of Muriatic Acid over 4 days. Day one 50%,day two 25%, day three 15% and day four the last 10%. I slugged in six areas the recommend amount on day one and two, turning off the pump and after 8 hours turned the pump back on each time. I checked my numbers last night and my TA has dropped to 120 ppm which is great but my PH has collapsed from 8+ to 7.0 .
NOW I am concerned about the PH drop and am worried about completing the last two treatments of Muriatic Acid 15% today and 10% tomorrow? Since a PH of 7.0 is neutral and once I start the SWCG the out-gassing of CO2 is going to cause a rise in the PH anyway is this a non issue? I had read some recommendations on this forum that I should keep my PH @ a minimum of 7.6 better 7.8 and and I should raise my CYA to 80-100 ppm. I am not sure who it was that wrote the guide for the SWCG pool chemistry numbers. I haven't been able to find it again!
I had read that if your CYA had disappeared it was due to Algae over winter. But my pool had no signs of Algae when I removed the cover last month and the CYA is rebuilding from the Calcium Hypochlorite tabs and my Free CL is staying stable between 3.5 and 4.5 ppm. My CBCL has remained at 0 ppm !
Any advice will be greatly appreciated

Do NOT add any more acid!!!!

However if your pH is 7.0 or above, you don't have to try to raise it, either.

There's no need to raise your pH for your SWCG, but you don't have to try to lower it, either, once it begins to go up.

I wasn't clear on what you were saying -- did you lose all your CYA over the winter, or not? Did the brown scale go away?

Notes:
+ Cal hypo does NOT raise CYA. Calcium, yes. But not CYA. You don't want to use a lot of that, on a pool with an SWCG.
+ High CYA is not a necessity, but it lowers chlorine usage and extends your SWCG life.
+ Don't trust that Taylor booklet much -- it's the worst thing about that kit.

I did loose all my CYA during the 7 months the cover was on my pool. I had about 15 pounds of HTH Calcium Hypochlorite tabs left over from when I switched to the BBB method 2 years ago. I thought it would be a good opportunity to use Calcium Hypochlorite tabs up since my testing showed my CYA had disappeared. My last test 3 days ago show CYA back up to @ 30 ppm. I am almost out of tabs so I will have to use CYA powder/granules to raise it the rest of the way to 80ppm I read on this forum is recommended for SWCG systems.
I still have the brown scalling on my liner. I was reading some info on metals in the water causing this problem! Then I remember finding my alluminum pole that I attaché my brush head and net too for cleaning the pool on top of the cover late last winter. The blue anodized coating on the pole had disappeared and the pole had a some what oxidized look to the aluminum that the pole was made of! Just a thought.
After following the Taylor K2005c test kits instruction on lowering the TA I have made 3 of the 4 days acid treatments so far or about 90 % of the total acid they recommend to make my correction. I will not add the last dose tomorrow. After reading this evening the procedure recommended on pool forum I started aerating my pool. What do you recommend from here? Thanks for your help !!

I think you may have missed what Ben stated in his post above. Cal-hypo does NOT add CYA.

Watermom, thanks for ringing in on my post!
I had to go back and take a 2nd look @ the containers my chlorine tabs came in. When I first purchased the home 2 years ago I inherited my Doughboy pool. My pool had originally been on bromine for sanitation. I drained and refilled my pool and started using Trichlor-triazineirione tabs after that. Some where along the way I had purchased 15 pounds on Cal-Hypo. I had quit using all the tabs when my CYA reached 50ppm and switched to the BBB method.
I installed a cover for the first time last November and I pulled my cover off in the middle of July, add when I tested the water I found the CYA was gone. I ran the CYA test 3 time and same results, O ppm CYA. I thought I would use the tabs I had left over from two years ago to reintroduce CYA into my water. I have used about 6 pounds of Tri-Chlor I had left and the started using the Cal-hypo. Sorry for the confusion. I assumed wrongly both types of tabs contained CYA.
Anyway when I used up the Tri-Chlor I had about 4 days ago and my test @ that time showed 30ppm CYA. I started aerating last evening and checked my PH and TA again @ 2:00pm central time. My latest test show PH 7.6 and TA 100ppm . At this point do I need to add CYA powder/granules to 80ppm before I start my SWCG for the first time?
I do still have brown scaling on the bottom of my liner where it makes the transition to the wall. This showed up after last winter with a cover on or the first time? I have read on the Forum about possibly some metal getting into the water? Any ideas about that? Thanks again !!!

I'm a little confused.

Could you list -- just a single list -- of your most recent COMPLETE chemical tests: FC, pH, TA, CH & CYA?

By the way, I took your test values OUT of your signature; those values will change, and leaving them in your signature could mislead someone into giving you wrong advice. And, as it is, I wasn't clear on what the date of those values was.

Here are my test results as of 7:00pm central time today.

FC: 2.0 ppm
CC: 0 ppm
pH: 7.8
TA: 100 ppm
CH: 90 ppm
CYA: 50 ppm
Borates: 30 ppm
Temp - water: 80F, air: 95F

Pool had just been covered with shade for the day!
Thanks

OK, thanks.

Now, what are your current questions? I'm guessing they are:

1. How do I remove the scale?
2. Do I need to do anything else?

I'll answer those two, in any case:

1. Lowering your pH to 7.0 and keeping it there will cause your TA to drop, slowly. Low pH and low TA will maximize your chance of removing the stain / scale.
2. I would recommend testing the stain / scale to see what will remove it. You can do so by holding various chemicals against the stain / scale for a couple of minutes. I'd recommend testing in this order:

1. Vitamin C tablets
2. Dichlor or cal hypo granular chlorine.
3. Iron Out powder
4. Sodium bisulfate (pH Down aka dry acid)

You should wear plastic gloves, and put the chemicals in #2 - #4 in a old (but clean) wash rag.

Let me toss in MY two cents:

As much as we love the Taylor K2006 test kit (which, using your K2005 with the K1515 is the same thing) their advice about lowering T/A is nonsense and can damage your pool. Please don't use the "Slug" method, because IF it works, it's only by accident, not because the "theory" (ie myth) behind it is any good.

As Ben pointed out, lowering your pH will lower your TA, but raising your pH after will raise TA back up again. The way around this is to lower pH as Ben said to about 7.0 and test your T/A.
If it's now good, when you want to raise pH again (after you have followed Ben's instructions for treating the stains) you'll raise it by aeration, not by adding any chemicals. That's by using a sprayer, splashing kids, pointing the return at the surface so it bubbles, etc, which will raise pH. Since your TA is now 90 you should be at a pretty good level. If it was STILL too high, you'd repeat by lowering pH to 7.0 again. So the "Slug" lowers the pH and with it the TA and whatever aeration you get raises the pH safely back up. But the "slug" is not what works--the lowering of pH does.