Pool math recommended FC levels

poolnoobgrandma

Well-known member
Sep 15, 2018
214
Seminole, FL
I've been using the pool math app, and we started with the SWG a couple of weeks ago. My settings are that we have a SWG and a plaster pool. PB target level sheet says FC 1-3 ppm. Pebble tech says 2 - 4.
App is stuck on a target of 3 - 10. How can I make the app reflect my pool's target FC range? All the other pool math target numbers are at least close to the pebble tec and PB recommendations.

Thanks!
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,260
Tucson, AZ
You shouldn't. The app recommended FC levels are set based on your CYA level according to the FC/CYA Chart.

If you try to keep the FC too low for your CYA, then you are bound for algae and an unsanitary pool ... forget about recommendations from other sources that are not taking the CYA level into account.

 
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Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,948
NW Ohio
Your target FC range is based on your CYA level, per the FC/CYA Chart. Most in the industry lack the knowledge of how CYA and FC are related so they just give those extremely low numbers. Numbers that are absolutely correct in a pool with no CYA, but quickly become inadequate when the FC is buffered by the presence of CYA. CYA also protects chlorine from the sun so it's not a good idea to attempt running an outdoor pool without it.

The app takes your CYA level in to account when giving you its FC range.
 

poolnoobgrandma

Well-known member
Sep 15, 2018
214
Seminole, FL
PB target level sheet may have been correct for the first 28 days of new plaster. Now you should use TFP targets for your CYA level FC/CYA Chart
OK... so the CYA requires that we target somewhat higher FC numbers, but ALSO reduces the FC loss, so that in terms of SWCG run time, it's a wash?

Odd that Hayward and Pebble Tec (not just my PB) have those lower FC targets (with CYA of 70 targeted as well.)
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,744
Northern NJ
OK... so the CYA requires that we target somewhat higher FC numbers, but ALSO reduces the FC loss, so that in terms of SWCG run time, it's a wash?

Odd that Hayward and Pebble Tec (not just my PB) have those lower FC targets (with CYA of 70 targeted as well.)
Hard to comment on musings without specific numbers or references.
 

poolnoobgrandma

Well-known member
Sep 15, 2018
214
Seminole, FL
111422
That's from a Hayward pamphlet: https://hayward-pool-assets.com/assets/documents/pools/pdf/literature/SaltChlorination-guide-LITSLTPAMP16.pdf?fromCDN=true

From Pebble Tec:

First, test the water to determine the current state of your pool balance. These are the ideal ranges:

  • pH: 7.2 to 7.6
  • Free Chlorine: 2 to 4 ppm
  • Total Chlorine: No higher than the Free Chlorine
  • Total alkalinity: 80 to 120 ppm
  • Calcium hardness: 200-400 ppm
  • Cyanuric acid: 30-50 ppm
I'm not here to argue. I am NOT an expert. I am doing my tests and feel comfortable that I can get to whatever numbers we need to. But these are the two companies that have supplied all my equipment, and I would think that they would have some knowledge.

Right now, since 3-4 falls in all three charts, that's where I'll target my FC, and won't fret about the poolmath app.

cheers...
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,422
Laughlin, NV
Your choice to not follow TFP recommended levels. We know they work, are safe, and provide the best path to a Trouble Free pool experience.
 

poolnoobgrandma

Well-known member
Sep 15, 2018
214
Seminole, FL
Your choice to not follow TFP recommended levels. We know they work, are safe, and provide the best path to a Trouble Free pool experience.
If I target 3 - 4 ppm, I AM following TFP recommended levels.
I'm just aiming at the lower end, and not fretting about the high end (10) of the FC target on pool math.
 

IceShadow

Gold Supporter
Jun 8, 2019
1,072
Milwaukee, WI
Sure, but if you have a sudden spike in FC usage (bathers, high UV from sun day) you could go below 3, and then have an issue that requires the FC to go very high to SLAM and resolve.

See Donaldson's post above. The industry doesn't take into account that CYA locks up a lot of the FC as part of what it does, and so very little active chlorine is actually available unless your FC is higher to compensate. This site does, and that's why people here have less algae outbreaks.

Those manufacturers probably don't blink twice when people drive their FC up to astronomical levels once a week to "shock" pools, either, which isn't necessary with the methods here.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,260
Tucson, AZ
Those manufacturers probably don't blink twice when people drive their FC up to astronomical levels once a week to "shock" pools, either, which isn't necessary with the methods here.
And this kind of action, which is "normal" to the pool industry, would arguably put your pool and equipment at MORE risk than just always maintaining the proper FC for your CYA like we teach.
 
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jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,260
Tucson, AZ
There will never really be a steady state for the FC. The weather every day will impact how much is lost to the sun. On a cloudy day, the FC will climb here than it will on a sunny day.