Chlorine/CYA Balance

[jason.jammer]

Hi Everyone,

I reviewed the chart and watched the video but want to get more of an idea of where I should target my CYA. I tested today and my results are FC- 3.6 and CYA- 35. Should I be targeting 70 like the charts recommends? I pretty much ran the same numbers last year and had no algae and my water is crystal clear. My pool does get direct sunlight with no shade. So sunlight is hitting my water from sun up to down.

Thanks,

Jason

 

[mknauss]

If you are satisfied with the FC loss each day and having no issues, then the lower CYA is fine. I would suggest not letting the FC get below 4ppm.
Your FC loss per day should be no more than 3 ppm in your climate.

 

[mknauss]

I also would suggest testing your FC at mid - day (say 2 or 3 pm) to see if your FC dips during the high UV time of day.

 

[jason.jammer]

I also would suggest testing your FC at mid - day (say 2 or 3 pm) to see if your FC dips during the high UV time of day.

I will do the mid test. Normally during the day I'll turn the spa on for 1-2 hours for the kids but that leaves the pool unfiltered and not generating chlorine. In the past I tested around 6pm and my FC is around 1.7 to 1.8. So my loss is no greater than 2.

 

[mknauss]

You should never let your FC drop below 3 ppm. That is the issue with low CYA and a SWCG.

 

[jason.jammer]

You should never let your FC drop below 3 ppm. That is the issue with low CYA and a SWCG.

Ok so you hit the root of my question. The sun is burning a lot of my chlorine during day. Can you recommend what I should raise my CYA to stop the loss?

 

[mknauss]

I have to have mine no lower than 70 ppm. You might get away with 60 ppm.

 

[jason.jammer]

I have to have mine no lower than 70 ppm. You might get away with 60 ppm.

Thanks for all the help Marty. I really appreciate your time. I'll start raising the CYA and testing during the afternoon and see what the best number is to prevent loss.

 

[jason.jammer]

Thanks for all the help Marty. I really appreciate your time. I'll start raising the CYA and testing during the afternoon and see what the best number is to prevent loss.

I wanted to report back. I raised my CYA to 55 and for the past two days I'm steady at 3.4 FC and my SWG is set to 85%. Not sure how to get to 4ppm unless I go up to 90%. Does that sound right?

 

[mknauss]

Your SWCG is very small for your pool volume. You need to run nearly 100% at 24 hours per day to achieve your FC needs.

 

[Jeff J.]

I wanted to report back. I raised my CYA to 55 and for the past two days I'm steady at 3.4 FC and my SWG is set to 85%. Not sure how to get to 4ppm unless I go up to 90%. Does that sound right?

Just so you know, the CYA test is not precise enough to measure 55. You round up to the next 10, so 60.

 

[mguzzy]

I wanted to report back. I raised my CYA to 55 and for the past two days I'm steady at 3.4 FC and my SWG is set to 85%. Not sure how to get to 4ppm unless I go up to 90%. Does that sound right?

Howdy Jason.. we have found that you should get an SWG that is rated for twice the volume of your pool... with a 23K gallon pool a T-15 rated for 40K would have been better fit. That gives you some elbow room to turn it up or down to suit the conditions without having to run it full bore all the time just to meet your minimum demand.

So as Marty says.. you are going to have to turn that puppy up.

 

[jason.jammer]

Just so you know, the CYA test is not precise enough to measure 55. You round up to the next 10, so 60.

I think I can round down to 50. I was closer to 50 than I was to 60.

 

[jason.jammer]

Your SWCG is very small for your pool volume. You need to run nearly 100% at 24 hours per day to achieve your FC needs.

Even though the T-9 is up to 25,000? My pool volume is 21,600 without adding my spa.

 

[mguzzy]

The ratings on the SWG are based producing a given amount of Cl running them 24/7 at 100%. So having a 25K SWG on a 23K pool is right at its limit. If you had a 40K SWG you would be able to run at 50% for the same time to create the same amount of chlorine (more or less).

 

[jason.jammer]

Howdy Jason.. we have found that you should get an SWG that is rated for twice the volume of your pool... with a 23K gallon pool a T-15 rated for 40K would have been better fit. That gives you some elbow room to turn it up or down to suit the conditions without having to run it full bore all the time just to meet your minimum demand.

So as Marty says.. you are going to have to turn that puppy up.

This is interesting. My pool volume is 21,600 without adding my spa. Believe it or not Hayward just sent me a new T-9 under my warranty. I wonder if I can change this out?

 

[Newdude]

If they let you pay the difference on the bigger model it would be worth every last penny. Alot of warranties wouldn't allow it though. They are usually like for like with no exceptions. It can't hurt to try though.

 

[PoolNewb2020]

I think I can round down to 50. I was closer to 50 than I was to 60.

It doesn't matter how close it was to 50 or 60, if the dot disappeared between these two numbers, you round up to the next one on the scale. Your CYA reading is 60ppm.

 

[jason.jammer]

It doesn't matter how close it was to 50 or 60, if the dot disappeared between these two numbers, you round up to the next one on the scale. Your CYA reading is 60ppm.

Thanks for this info. I wasn't aware.

 

[jason.jammer]

One detail that I didn't report was my ph is 8.0. I used pool math to lower to 7.6. Could my high ph be causing my CL not to be producing at a higher number? My AL is at 90.

My CL this morning was at 3.2 after 11 hours of not running my pump and SWG. So raising my CYA to 60 seems to be working since my CL reading yesterday afternoon was 3.4.