Low CH in a fiberglass pool

Sep 20, 2018
67
N TN
Pool Size
20000
Surface
Fiberglass
Chlorine
Liquid Chlorine
I just tested my water in preparation for closing and discovered that it is only around 100. The manufacturer of my older fiberglass pool recommends a minimum level of 200. Since the pool is going to be covered with a mesh cover for the next 7 months and the water level will be below the tiles all winter, do I need to add 18 pounds of calcium to the water to increase it to 200? Would I be putting my gelcoat at risk if I closed with calcium at 100 since we normally open up to some algae and lots of leaves in our pool? If I need to add calcium, I could use some advice on how to get it to dissolve in colder water and how much to add at one time, since I had difficulty getting it to dissolve in the past. I know from experience that calcium gets quite hot when added to water, so I'm not sure I feel comfortable with dissolving it in a bucket of water and pouring it into the pool.
 
I just broadcast it from my deep end. What I get dissolves instantly.

If you close based on water temp being below 60 and open before it hits 60 you'll never open to algae.
 
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