CYA Chart is different than app? Trying to understand why.

[Yarzy]

Hi Everyone! I am still VERY new to the pool world, only having our new pool for little over 1.5 months now. I have been testing the water daily per the TF-Pro Salt test. Because of the changeover to salt, in the app I made the change as well, telling the app is it using SWG. My question is, if I look at the CYA/FC chart on the website, it says with a CYA level of 95 (high, I know), I should have a FC level of 4-6/4-7. On the app, it says 4-13? Any idea why that is? Just so you have all the info, here are all my numbers:

24k pool
1.25 24 SWG output
Plaster

Numbers:
FC-2.5
PH-7.5
TA-80
CH-225 (going to the store today to bring this up)
CYA-95 (I am hoping this was due to the salt being added as 5 days ago it was 60
Salt - 4000 (what should range be)
85 degrees water temp

I am sure I am not reading something correctly, but I cant understand why the FC is saying 4-13 when the chart is more like 6/7. Any ideas? Thanks!!!!

 

[cowboycasey]

You FC number is way low... You probably need to do an Overnight Chlorine Loss Test check just to make sure you have nothing growing...

With a CYA of 95> we say 100 as there is no 95 the recommended FC is 7.. I run my pool at 7 FC and I have CYA at 80.. I would recommend you run your FC level at 8...

The minimum is a cliff, you never want to drive off a cliff and you never want to get near a cliff... With a SWG you really want 8 FC at all times 24/7 I run my SWG during the day and keep it at 7 FC, during the night the FC stays at 7 and the pump/SWG turns on at sunrise..

As for the app I am not sure, it should have said it was 7 for the recommends just like this.. Chlorine / CYA Chart - Trouble Free Pool
It is showing the FC level for a non SWG pool...

 

[mknauss]

The app is giving the entire FC range with minimum for SWCG and upper target for manually added chlorine. Your FC right now is way too low. Add liquid chlorine.
@Leebo -- we might want to look at that in future updates.

The salt addition did not raise your CYA. So you have added too much stabilizer. It would be best to replace about 20% of your pool volume. You can try to drain some when you will be getting rain, etc.

3000 - 3500 ppm salt is best. Your SWCG will stop generating at 4000 ppm. So watch that.

 

[Yarzy]

Thanks everyone. So they just switched the SWG on this morning. I have it set right now for the pump to run 24/7 and SWG at 60%. FC has been right around 3.0 for a week now with tablets but they are gone now that the SWG is on. I did not add any stabilizer at all but perhaps my PB did when he came this morning to flip on the SWG. I will monitor it for sure but is it possible the SWG will "make up the difference" now that it is on and making chlorine, bringing it back up to a more acceptable level? I will add as needed but if I can be patient and have it climb back up, I would rather do that. I guess I am asking if the increase is even possible at this point or am I too close to the cliff.

Thanks again!

 

[cowboycasey]

SWG suck at raising chlorine.. raise FC with liquid chlorine then let the SWG maintain that FC level.. They are GREAT at maintaining it

 

[mknauss]

The SWCG is creating 3.8 ppm FC per day as you have it set. That will be close to your daily consumption at this time of year. At a CYA of 100, you need to add liquid chlorine. Now.

 

[Yarzy]

ok, I will add it now. How much should I add?

 

[Yarzy]

Sorry, one other question. I have some left over bags of shock. Can I use them vs liquid?

 

[Newdude]

I have some left over bags of shock

They have either CYA or Calcium in them. Save them for vacations or a future date that either value is low.

How much should I add?

Download poolmath for free and setup your info. Gallons, finish, etc. click on ‘FC’ and enter where you’re at and where you want to be with liquid bleach (adjust the % per the bottle label). It will tell you what to add. Get familiar with the app. It will be your best friend.

 

[Yarzy]

Happy to report that my FC is back to 5. I did not add anything yesterday and it looks like the FC is slowly creeping back up. PH was up so I added some acid but I think we are good to go. Thanks everyone!