Background
I live in Utah where we get cold snowy winters. This is the third year closing my pool so I'm becoming a pro at it. I'm meticulous about checking and balancing chems daily & weekly when the pool is in operation. In preparation for closing, 7 days ago I shocked using 7.5% bleach to raise FC to 16.5. In previous years over the course of the week the FC would slowly drop to a reasonable level by the time I closed the pool. This year, however, we had a cold snap and pool temps plummeted from 70's to 50's (Fahrenheit) and the chlorine level is not dropping. I tried forced aeration (using this method My $5 Return Jet Aerator) to off-gas to reduce chlorine levels and this has worked in the past but is not working this time.
Levels as of yesterday (10/27/2022):
FC: 16.5
pH: 7.7
TA: 60
CH: 300
CYA: 40
Temp: 54F
Questions
1) Will closing the pool with FC that high damage the vinyl liner or winter cover (thick winter tarp material)?
2) Should I consider using Sodium Thiosulfate to reduce chlorine in this case?
I live in Utah where we get cold snowy winters. This is the third year closing my pool so I'm becoming a pro at it. I'm meticulous about checking and balancing chems daily & weekly when the pool is in operation. In preparation for closing, 7 days ago I shocked using 7.5% bleach to raise FC to 16.5. In previous years over the course of the week the FC would slowly drop to a reasonable level by the time I closed the pool. This year, however, we had a cold snap and pool temps plummeted from 70's to 50's (Fahrenheit) and the chlorine level is not dropping. I tried forced aeration (using this method My $5 Return Jet Aerator) to off-gas to reduce chlorine levels and this has worked in the past but is not working this time.
Levels as of yesterday (10/27/2022):
FC: 16.5
pH: 7.7
TA: 60
CH: 300
CYA: 40
Temp: 54F
Questions
1) Will closing the pool with FC that high damage the vinyl liner or winter cover (thick winter tarp material)?
2) Should I consider using Sodium Thiosulfate to reduce chlorine in this case?