FC overtime if CYA is zero

[engrav]

Hi

CYA is zero as we are starting up after new plaster.
Had an algae bloom that cleared with SLAM, passed OCLT.
Now letting FC drift down.
Pool looks fine.

However last evening FC 7.5 at 4 pm
This AM at 5:30 am FC 5.5

Assuming no algae, and with no CYA, will FC drop overnight?

Thanks

 

[PoolGate]

Could be an anomaly with the test. Just test again and go with what you get. You could have also hit a cloud of chlorine last night. Get some CYA in there!

FYI: Chlorine always drops some especially with that time-frame.

 

[engrav]

Could be an anomaly with the test. Just test again and go with what you get. You could have also hit a cloud of chlorine last night. Get some CYA in there!

FYI: Chlorine always drops some especially with that time-frame.

thanks

re-test, same, 5.5

builder using Orenda startup plan that includes no CYA for 30 days, am at day 20, plan linked below

https://www.dropbox.com/s/nsd36fk66x11722/Orenda%20Startup%20Tank%20Procedure%20Page.pdf?dl=0

ok will assume 2 pt drop overnight with no algae no CYA no sun is Ok, how life is

thanks

 

[engrav]

follow-up

today (no sun), pool temp 46, FC dropped from 5.5 to 3.5
confirming lability of FC with no CYA even with no sun

is interesting to me
with CYA say 20-30 a gal of chlorine lasts weeks in our cloudy winter weather