Dichlor/bleach method: High CYA on first dose of dichlor after fill?

[angromarsi]

I used dichlor for about 3 weeks on my first fill before I realized I had sky high levels of CYA.  From there we drained half the tub (middle of cold winter), filled fresh and used bleach.  We drained the tub for the first time since ownership this week.  Ran some ahhsome through it before hand just in case as I broke out in a rash last time I used it (but could have been excema too).  Water was clear but not as sparkely and became cloudy easily (chlorine dropped if we didn't go out every other day).  Husband wiped down tub after use washed filter and then filled it.  First reading on dipstick before I broke out the Taylor test kit had 0 stabilizer. 

Last night I had these readings (Taylor) from the fill:
pH: 7.8
TA: 45 ppm
CH: 80 ppm

Added approx 2 oz CH to get it to around 120 ppm per Pool Math Calculator; added 23 oz by weight of Borax to get to approx 50 ppm (I don't have a test for this)
Unfortunately, I only had 2 oz of dry acid left and didn't realize it until after I added the borax.    I added .75 oz of dichlor last night to get the FC to about 7.0 for overnight (didn't want it sitting without clorine overnight). 

Went out to buy muriatic acid today, did the dipstick to see where the chlorine
My pH has been sky high today and I've added 8 oz muriatic acid followed by another 4 oz.  I'm still over 8 ph but only have 3 drops to 7.6 per acid demand test vs the 15 I had after the 8 oz application. 

So now I'm at ph > 8.0 (3 drops acid demand)
TA 70 ppm
CH 90 ppm
With borax
FC 0 ppm
I haven't done the CYA test with the Taylor kit b/c I'm runnng low and don't want to use it all up. 

So thoughts?  Should I add more dichlor?  Should I move onto bleach after only .75 oz?  WWYD?

[chem geek]

For every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases Cyanuric Acid (CYA) by 9 ppm.  So it doesn't take too long with heavy usage for the CYA to get up high.  Usually you switch over to using bleach after having cumulatively added 33 ppm FC so with daily usage that might be after only a week.

We usually recommend getting boric acid (say, from Duda Diesel or The Chemistry Store) rather than using Borax and Acid because it's easier and doesn't swing up and down in pH during addition.  Also, you should NEVER add all the Borax at once because it would cause the pH to go through the roof and potentially cause scaling (depending on your TA and CH levels).  You are supposed to split up the doses and alternate between Borax and acid.

At this point you should add more acid to get your pH in line.  If I understand the sequence correctly, you complete drained the tub so you should still use Dichlor until you've cumulatively added around 33 ppm FC.  So far you've only added 7.

[angromarsi]

Thanks!  I'm thinking the pH was sky high so the test strip wasn't working.  After getting the pH back down to normal, the stabilizer readings went back to close to zero as well.  Still using dichlor and appreciate the response!