Expected amount of FC to rise per day?

[Yarzy]

Hi everyone,

I am in my 2nd year of new pool ownership and I had a question. We run our pump 24/7 at 1200rpm. Salt system seems fine with no flow errors, etc. Last year, I could have swore I did not set my SWC more than 30% and I was good on FC. I went back and looked and I was well over 5, sometimes 7-10 FC. (too high, I know). This year, I am at 40% with 2 "extra" chlorine pucks in the skimmers just to make sure all is well. I dont plan on keeping the pucks in there all the time, i will explain why I added them in the first place. A few days ago, I tested the water (TF Pro 100) and my FC was at 2.5 with a CYA around 90, my SWC was at 30%. My FC was too low according to the pool math app. I upped my SWC from 30%-40% and added the pucks just to make sure nothing was weird with the SWC because again, I dont think I went over 30% all last year and I was well over 4, more like 7-8 on average. I am trying to understand two things. 1) About how much FC is expected to raise each day with a 5% increase? I know sunlight, etc will have major impact but any ballpark number? 2) Any idea why even though my levels were similar, I was so much higher in FC last year? I am talking I was 7-8 in the dead of August. Pool stays super clean, etc. I just can't figure it out. The only thing different is last year I ran the pump for a few hours a day on a higher speed. Does a higher RPM create chlorine faster? For reference, here are my numbers currently:

FC - 4.0
Ph 7.7
TA - 70
CH - 375
CYA - 70
Salt - 3400

Thanks!

 

[Mdragger88]

If your cya is already 90 the pucks aren’t doing u any favors. Or is it 70? U said 2 things. This definitely matters when it comes to fc levels.
Supplement your swg with liquid chlorine to at least target level now. FC/CYA Levels
Do an Overnight Chlorine Loss Test to rule out algae.
A clean looking pool can still have nascent algae lying in wait especially if u have gone below minimum for your cya. Better to catch it now.
Fwiw - running fc a dab higher than target isn’t hurting anything- it actually protects u from broaching minimum as u are now FC/CYA Levels
The average pool consumes 2-4ppm of fc/day
Your current swg settings are barely in range to produce that. Its more likely that u need to up the % to at least 50% during peak summer. Lets see what the oclt says.

 

[Newdude]

Hey Yarzy and Welcome back !!!

So your cell should make 6.35 ppm FC per 24 hours in your pool. (Maths away that 40% is 2.54ppm a day, etc)

If last years UV was lower than this ones so far, it could be about right.

Overnight Chlorine Loss Test just to ensure there is nothing eating up your FC.

 

[Yarzy]

Thanks everyone! Just to clarify, my CYA is at 70, I did not mean 90. Based on the chart, it looks like at a min, I should be at 5 FC. Is it possible it will be there by tomorrow AM? I wonder if I just wait a day or two to see how it goes (and if it goes up) would be an idea.

I will do the test as well and see what happens. Thanks again!

 

[Jimrahbe]

Y,

I never try to run my SWCG between the minimum and my target, just too much work always adjusting things up and down.

I try to keep my FC at my target or higher. Higher is never an issue. I look at my minimum as a cliff that I never want to fall off.

Thanks,

Jim R.

 

[Newdude]

Huge +1. I am dialing in a new SWG right now at 10 FC. (70 CYA). I won't blink unless it hits a teen and once the newness wears off, I likely won't catch it immediately in the teens. I'll laugh and shut it off for a couple days and start back at 10.

I could fiddle with it all the time and dance the razors edge at minimum but I specifically bought it for less work, not more.

 

[wireform]

You also don't want to put the pucks in the skimmer as it'll destroy the heater core .

 

[Mdragger88]

A Better plan is to raise fc now (to target level or above) with liquid chlorine & see if it keeps up after turning up the swg.
Swg’s are great maintainers but they take time to produce fc - u don’t want nasties proliferating in that time. Running a little “hot” is way safer than skirting minimum.

Also doing an Overnight Chlorine Loss Test to rule out organics consuming your fc is wise.
A strong swg can hide an algae problem but not forever. The 1st sign is generally increased fc demand.

 

[Yarzy]

Well, I figured out my issue...it turns out the SWC was not making Chlorine...I noticed a message on the app saying there was a flow issue. I backwashed, cleaned the pump filter, took out and inspected (and cleaned) the salt sensor and we have not had that error in two days so I think I am good there. The FC is climbing as well so I think that was my issue.