A few testing result questions

[LisaDLu]

Hello - My FC has hovered between 6.0 and 8.0 for the last 4 weeks (TA has been 70 for the same period). I tested yesterday and my FC is now at 4.0 and TA is still 70. My question is if my TA is constant what would cause my FC to drop in the last week (I do a full set of tests each weekend). Are temps have been in the mid to high 80's, and our salt has been reading 2900 to 3000 with a 50% output. We have only been in the pool twice in this period.

Yesterdays results:
PH - 7.8
TA - 70
FC - 4.0
CC - 0
CYA - 60
CH - 360
Salt - 3000
Water temp - 74 degrees
Sat. Index - 0.1

Also, my CH has been slowly creeping up each week (we replastered in January). Since the weather has heated up I am adding some fill water about 1 - 2 times a week and we do have hard water here. The guidelines here for saltwater pools is to keep CH between 250 and 350. At what high point of CH should I consider lowering it? We are in a severe drought so really don't want to partial drain). Thanks!!

 

[JasonLion]

TA and FC have nothing to do with each other.

Chlorine usage varies from day to day based on many factors. Water temperature and sunlight intensity are two of the bigger factors. People are not at all good at judging sunlight intensity. FC will also be different at different times of day. So you can only compare one day to another if both tests were done at the same time of day.

On CH, test your fill water to see how much of an issue CH is going to be for you.

You don't need to do anything at all until CH is around 500. High CH levels can be managed up to roughly 1,000, but it takes more and more work as the CH level goes up.

 

[LisaDLu]

Oops! I talked about TA but meant to talk about CYA. Regardless, you answered my questions. Thanks!