I struggled for over 6 weeks with a conversion from Baquacil to chlorine. I was very disciplined about testing and using the Pool Calculator to maintain the 15ppm FC level. My water cleared up within a week, but the CC level never dropped off. It just stayed between 4 and 9 ppm for weeks. I tried replacing the filter sand and making sure everything was spotless - still no joy two weeks later.
Finally, I decided to drain and refill since this was pretty easy for me to do. It took about 3 hours to drain the pool using the filter pump discharging to waste. Then about 6 or 7 hours to refill with two garden hoses feeding into the pool. So, after one day, I had fresh water.
Day two I added CYA using granular stabilizer in a filter sock hung in front of the return jet. That took about 8 hours to dissolve.
Then I brought the FC up to 6ppm with liquid chlorine after sunset on day 2. I waited an hour or so and tested to confirm I had the desired level of FC. I did. Early the next morning, I tested the water again and low and behold, I only had 0.75 ppm CC and the FC dropped by about 1ppm.
The evening of day 3, I again brought the FC level up to 6ppm. In the morning, I still had about 6ppm of FC and CC was at or below 0.5 ppm. pH has been good at about 7.3 or 7.4. The other readings are also in range (for a vinyl AG pool).
So by draining and refilling, I was able to do in about 3 days, with very little effort, what I couldn't do in 6+ weeks of constant work and large quantities of liquid chlorine. Total cost for the failed "traditional" conversion: $80 in chlorine, $50 in testing supplies and 50+ hours of labor. Total cost for the drain and refill: $4 in chlorine, roughly $2 in testing supplies, and 3-4 hours of labor. There might have been a few dollars of electric power to run our well pump to refill, but that was more than offset by the power used to run the pool filter pump for 6+ weeks 24 hours a day during the failed conversion.
If draining and refilling is a viable option for you, I strongly recommend it over the normal conversion routine. It will almost certainly be cheaper and quicker with more certain success.
Finally, I decided to drain and refill since this was pretty easy for me to do. It took about 3 hours to drain the pool using the filter pump discharging to waste. Then about 6 or 7 hours to refill with two garden hoses feeding into the pool. So, after one day, I had fresh water.
Day two I added CYA using granular stabilizer in a filter sock hung in front of the return jet. That took about 8 hours to dissolve.
Then I brought the FC up to 6ppm with liquid chlorine after sunset on day 2. I waited an hour or so and tested to confirm I had the desired level of FC. I did. Early the next morning, I tested the water again and low and behold, I only had 0.75 ppm CC and the FC dropped by about 1ppm.
The evening of day 3, I again brought the FC level up to 6ppm. In the morning, I still had about 6ppm of FC and CC was at or below 0.5 ppm. pH has been good at about 7.3 or 7.4. The other readings are also in range (for a vinyl AG pool).
So by draining and refilling, I was able to do in about 3 days, with very little effort, what I couldn't do in 6+ weeks of constant work and large quantities of liquid chlorine. Total cost for the failed "traditional" conversion: $80 in chlorine, $50 in testing supplies and 50+ hours of labor. Total cost for the drain and refill: $4 in chlorine, roughly $2 in testing supplies, and 3-4 hours of labor. There might have been a few dollars of electric power to run our well pump to refill, but that was more than offset by the power used to run the pool filter pump for 6+ weeks 24 hours a day during the failed conversion.
If draining and refilling is a viable option for you, I strongly recommend it over the normal conversion routine. It will almost certainly be cheaper and quicker with more certain success.