Going from SWG to Bleach in Winter

[Bluelilly]

As the water temps drop and the SWG stops producing chlorine, we will obviously be using bleach for the winter. Pool will be left uncovered. With the recommended levels of CYA differing for SWG and Bleach methods, do we need drain pool to lower CYA? SWG recs 60 - 80 for SWG and Bleach is 30 - 50.

FC 5
CC 0
pH 7.8
CH 100
TA 90
CYA 70
Water Temp around 55

Thanks.

 

[duraleigh]

Interesting question.

Because of the lower temps and far less demand on your pool, I would not drain to reduce CYA but rather use the chlorinating values for a manually chlorinated pool and leave the CYA right where it is.

You will not use much extra chlorine and you will save the refill water and having to add back CYA in the Spring.

 

[jblizzle]

No need to drain the water to lower the CYA ... just use the recommended FC level for your CYA in the bleach table: FC/CYA Chart

With a CYA of 70ppm, just use bleach to maintain the FC > 5ppm.

With the colder water and less sun, the FC will not drop nearly as quickly as it would in the summer.

 

[Bluelilly]

Thanks for the info. That makes sense to keep the FC levels a bit higher.

 

[woodyp]

You may get surprised and have your CYA actually drop over the winter for reasons none of us really understand either. Also, just pumping out excess rain water if needed will also help lower it.