High FC - can cold temp affect my test?

[jimmychuck]

Hey everyone,

Water temps have been dropping here in SoCal and my pool has been 55ish for a few weeks now.

I lowered my SWG to 35% and am running the pump for 8 hours per day and am still getting higher than expected FC readings.

Today’s was 18 so I’ve dropped the SWG to 25% and will test again in a few days.

Pool was completed in February so this is my first year with it and I guess I don’t know what to expect. My last pool was in Texas and was not saltwater so the chlorine control was different.

Anyway looking for guidance in case I’m missing something.
TIA

 

[jimbethesda]

I currently lose .5ppm of chlorine a day. I don’t see your SWCG model in your signature. How many PPM will you create at 25% over 8 hours?

 

[ajw22]

The only test that we do that is affected by cold water is the CYA test. You should let the CYA water sample warm to room temperature before adding the reagent.

Your FC loss drops this time of year due to the low water temperature and lower sun angle and shorter days. Just keep on reducing your SWG %. As we get into the spring you will reverse the process and increase the SWG % as your chlorine use increases.

Yesterday was the shortest daylight of the year.

 

[jimmychuck]

Thanks AJ. Seems I’m on the right path then. Appreciate it.

 

[jimmychuck]

I currently lose .5ppm of chlorine a day. I don’t see your SWCG model in your signature. How many PPM will you create at 25% over 8 hours?

Hey Jim sorry just updated my profile.
I’ve got an IC40.

 

[jimbethesda]

Hey Jim sorry just updated my profile.
I’ve got an IC40.

According to pool math, an IC40 at 35% for 8 hours in a 22,000 gallon pool raises it by .9 ppm. If you’re losing .5 ppm/day like me, it will still increase at 35%.

My suggestion is that you turn it off for a few days, then remeasure. Then you’ll know how much you’re losing per day and can plan accordingly.

 

[Timujin]

FWIW I am running the SWG at 20% 10AM-4PM maintaining 6-6.5PPM.

 

[setsailsoon]

Below 60 deg algae growth is near zero. Also, usually swg FC production drops dramatically as well. I don't see this as a problem. You actually have a great cell and your FC consumption is just very low. If the high FC levels persist after dropping your % power I would just turn off the swg for a day and measure the FC loss. This will tell you how much you need and you can use Pool Math to estimate the swg settings. But do watch the weather. If you get warmer conditions it won't take long for FC loss to increase substantially. I like to run FC on the high end of the range for this reason.

I hope this helps.

Chris

 

[jimbethesda]

FWIW I am running the SWG at 20% 10AM-4PM maintaining 6-6.5PPM.

According to pool math, you are creating.5ppm per day.

 

[Rocket J Squirrel]

The only test that we do that is affected by cold water is the CYA test. You should let the CYA water sample warm to room temperature before adding the reagent.

Does cold water cause the CYA test to falsely read too high or too low?

 

[mknauss]

Does cold water cause the CYA test to falsely read too high or too low?

Too low. Let the water come to normal room temperature prior to the CYA test.