Chlorine burns off after 2 days

[JohnnyG]

So, my CYA is high (80-90ppm) and I'm trying a new routine this year to help bring it down.
(in addition to annual end-of-season partial draining. The draining has been helping, but not enough).

I've stopped using the Chlorine pucks this season, and only using Liquid Chlorine (Sodium Hypo).
I'm finding that I go through a Gallon or more per week - is this to be expected?
My FC levels keep for about 2-3 days, but drop off rapidly each day. For example, on 8/9 I added 96oz of Liq. Chlorine in the evening and ran the pump for 1-hour.
Tested FC next day (8/10) and it was 5.0. Tested again NEXT DAY on 8/11 and it was 2.0.

Water is CRYSTAL clear - my levels are (using Taylor K-2006 kit):
PH: 7.4 - 7.8
CYA: 80 - 90
ALK: 100
Calcium Hardness: 130
(I ordered a Taylor Phosphate kit to check that level)
CC: less than .5 - kit shows a very, very slight Pink indication and 1 drop of R-871 returns clear.
I've shocked the pool to FC: 6.0ppm twice so far, but CC remains unchanged.

Pool Specs:
=================
16x32 in-ground, approx 13,000 gallons (shallow pool. 3' => 5')
vinyl liner (brush scrubbed and vac'd 3 times this season.)
Gets full day sun - water temp: 82-84 F
Used basically just by myself, and that's maybe 2 times a week at most.

Thanks for your feedback. -John

[Denniswiseman]

With a CYA of 80-90 you would need to maintain a target level of about 10-11 to get correct sanitation as indicated in Chlorine / CYA Chart
Excessive CYA renders your chlorine ineffective and you have to use more to get the same sanitation
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
To reduce your CYA you have to do a partial drain and refill
Continuous use of Trichlor/Dichlor will raise your CYA which means you have to raise your chlorine level as well
You'll never get rid of your CC with those levels of chlorine, you need about 33ppm to Slam (Shock Level and Maintain)

[JohnnyG]

Thanks Dennis. I'll continue to work on getting my CYA under control as Step #1, then go from there.

[Denniswiseman]

You really need to get it down to about 40-50
You probably need to drain about 50% but that may be a problem in one go because of your liner