What level FC should be at during the winter with CYA at 80ppm

Hachu

Bronze Supporter
Aug 11, 2020
82
Dallas, TX
Hi. I live in DFW area and my pool is open during the winter. I'm curious what level of FC should I keep my pool at when my CYA is at 80ppm? I've been adding liquid chlorine to bring FC to 9ppm every week. After 7 days FC goes down to about 6ppm. I'm just curious if I should still follow the CYA/FC chart or I can just maintain a lower FC now that the water is colder? I don't want algae to be waiting for me when weather gets warmer or when we decided to use the spa. Thank you.

Today's tests
Temp: 48°F
FC: 6ppm
FC:0
pH: 7.8
TA: 80
CYA: 80
TDS: 525
 

HermanTX

Gold Supporter
May 20, 2020
1,162
Katy TX
Pool Size
14600
Surface
Plaster
Chlorine
Liquid Chlorine
I like to play it safe so the best way to avoid algae is to dose liquid chlorine daily or every second day. If you are dosing weekly you are starting high and letting it drop everyday. Even though it is colder, some days are sunny than others so you just do not know when your FC drops. Agree that you always keep FC at or above the recommended level per FC/CYA chart which for CYA 80 that is target 9-11ppm with absolute minimum of 6. You are risking potential algae if you miss your weekly dosing. Just evaluate the level of risk you are willing to assume.
 
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Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
8,363
Central California
Pool Size
12300
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
FC level is based on CYA, not weather. Chlorine will likely burn off more slowly in the off season, so you can probably get away with less frequent dosing (I do). But lurking around your FC minimum is risky, even in cooler weather. Remember, chlorine is used up by the sun, yes, but also by the organics that enter your water (that's its primary mission, after all). So while you might be able to rely on consistent weather, you can't rely on never having any errant FC-consuming events occurring, like leaves falling in the water, or bugs, or animals drowning, etc.

If you dose just once a week, it's likely that you're ignoring your pool for much, or all, of that week, too. If something crawls in your water on day 1 after dosing, and drowns in your skimmer, then it could tank your FC in a matter of days, leaving your pool FC free and susceptible. So you decide for yourself the amount of risk you want to take: how often you check your pool and equipment, how often you test, how often you dose...

One of the easiest pool tasks is a simple "drive by." Walk by your pad, look for leaks, listen for the pump running, glance at your filter gauge, then walk by the pool, check that the water is clear, peek into the skimmer. That's it, less than a minute. That's nothing compared to battling an algae outbreak, which can take hours and hours!

Want to play it safe? Mid week, dump in half your normal weekly dose of chlorine. If you're getting consistent numbers each week, it's a safe bet that dosing half the normal amount is going to be fine. You don't have to test. When it comes to chlorine, an extra cup or two will do nothing harmful, and will likely just be supplementing what has already burned off in those first few days. Then come week's end, you'll be much better off, FC-level-wise, than you would have been. That might add a minute to your "drive by" for just that one mid-week day!
 
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Waiawa

Silver Supporter
Dec 10, 2020
108
Round Rock, Texas
Pool Size
13860
Surface
Fiberglass
Chlorine
Liquid Chlorine
I know this question has been answered somewhere, I just don't know where.
How much ppm does a quart of liquid chlorine add to the pool?
 

Hachu

Bronze Supporter
Aug 11, 2020
82
Dallas, TX
I like to play it safe so the best way to avoid algae is to dose liquid chlorine daily or every second day. If you are dosing weekly you are starting high and letting it drop everyday. Even though it is colder, some days are sunny than others so you just do not know when your FC drops. Agree that you always keep FC at or above the recommended level per FC/CYA chart which for CYA 80 that is target 9-11ppm with absolute minimum of 6. You are risking potential algae if you miss your weekly dosing. Just evaluate the level of risk you are willing to assume.
Thank you! It makes sense.
 
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Hachu

Bronze Supporter
Aug 11, 2020
82
Dallas, TX
FC level is based on CYA, not weather. Chlorine will likely burn off more slowly in the off season, so you can probably get away with less frequent dosing (I do). But lurking around your FC minimum is risky, even in cooler weather. Remember, chlorine is used up by the sun, yes, but also by the organics that enter your water (that's its primary mission, after all). So while you might be able to rely on consistent weather, you can't rely on never having any errant FC-consuming events occurring, like leaves falling in the water, or bugs, or animals drowning, etc.

If you dose just once a week, it's likely that you're ignoring your pool for much, or all, of that week, too. If something crawls in your water on day 1 after dosing, and drowns in your skimmer, then it could tank your FC in a matter of days, leaving your pool FC free and susceptible. So you decide for yourself the amount of risk you want to take: how often you check your pool and equipment, how often you test, how often you dose...

One of the easiest pool tasks is a simple "drive by." Walk by your pad, look for leaks, listen for the pump running, glance at your filter gauge, then walk by the pool, check that the water is clear, peek into the skimmer. That's it, less than a minute. That's nothing compared to battling an algae outbreak, which can take hours and hours!

Want to play it safe? Mid week, dump in half your normal weekly dose of chlorine. If you're getting consistent numbers each week, it's a safe bet that dosing half the normal amount is going to be fine. You don't have to test. When it comes to chlorine, an extra cup or two will do nothing harmful, and will likely just be supplementing what has already burned off in those first few days. Then come week's end, you'll be much better off, FC-level-wise, than you would have been. That might add a minute to your "drive by" for just that one mid-week day!
Thank you. These info is very helpful. I do like to play it safe and will follow the advice.