Is low free chlorine okay?

[Rmd0627]

Hello.

I am looking for some advice. I have not been able to keep my FC above .5 since I opened my pool about a month ago.

When we opened it, we had about a 75% water loss. We re-filled the pool, Added CYA, and proceeded to balance accordingly. as of right now


CYA = 74
PH= 7.2
TA = 110
TC= 1.5
FC=.5


Is it ok to have the FC this low? I cant seem to get it any higher for more than a few hours.

thank you

 

[Texas Splash]

Hello and welcome to TFP! There's no doubt you have an issue with your current FC and CYA levels not balanced properly as noted on the Chlorine/CYA Chart (link below). Before we go too far though, would you mind clarifying how you got those test results? Was it from a TF-100 or Taylor K-2006 test kit perhaps? That will help us as we go further.

 

[Rmd0627]

I have been reading this site for a while and quickly learned to get rid of the test strips...I have the TK2006!

 

[ping]

We need to know your pool specs, please make a signature.

You need to run an OCLT to determine if there are any organics consuming the chlorine. Raise the FC level to at least 6ppm with liquid chlorine for the test and run the pump overnight. This test will determine if you need go through the SLAM process. Pool School - Perform the Overnight FC Loss Test (OCLT)

 

[Texas Splash]

I'll also add another comment to what ping noted above about the OCLT. If you're at a point where you can't seem to increase or maintain FC at all, not even to keep it around 5-6 ppm, then that's pretty significant. That would indicate you have something fairly aggressive in the water eating your free chlorine rapidly. At least you have the K-2006 so that's very good. For the OCLT you need to have at least 3 ppm of FC in your water, and I like ping's suggestion about trying to get it up to about 6 ppm. So what you may need to do first is, with a decent amount of bleach available, increase your FC to about 10. Then, re-test it in 10 minutes and see what you have left. If it dropped really fast, increase it again right away and keep doing that until it holds. Once you add your pool info into your signature we'll be able to guide you a little further.

 

[Rmd0627]

I have a 24' 15,000 gallon. Ok, so I should get it to about 6ppm, wait 10 mins and test, if it stays, then do the OCLT. If it doesnt hold, keep adding and testing every 10 mins until it does and then do the OCLT?

thanks for the help!

 

[ping]

Run the OCLT tonight.

For now, add enough bleach to raise the FC to 10ppm and retest in 10 minutes. If the FC is around 10 then retest in an hour. If the FC dropped to 5 or so add enough chlorine to raise it back to 10. Once the sun is down start the OCLT.

 

[BuckeyeChris]

while waiting to get the FC to hold at 10, you can use the 10 mL FC test. When testing at sundown/sunrise to see what you lost overnight, the extra precision of the 25 mL test might help.

 

[Rmd0627]

got it. if it doesn't pass the OCLT, next step is slamming? Just want to be prepared.

thank you!

 

[Texas Splash]

Yes. If you fail the OCLT the next logical step would be a SLAM (link below). You can read that page in advance just to get familiar with it if you've never done one before. Not the hardest thing to do, just requires a bit of consistency for best results. Good luck!

 

[Rmd0627]

Ok. So I went home and got the FC up to 10. After about an hour it was down to about 5. I brought it back up (this was after sundown) I tested it the next morning and it was at 5. After work I tested again and it was down to 3. It held steady there all night. Is this ok or should I take further steps to keep it higher?

 

[Mr Bruce]

It is better to do an OCLT at about 10. A 20% loss of 10 would be 8 (fail) and a 20% loss of 3 would be 2.4 (pass).

 

[BuckeyeChris]

After the sun goes down, test the FC, and add what you need to bring it to 10. Let the water mix 30 minutes, then do another FC test. Mark your FC number down.
Then retest the FC before sunrise.

You've got to do the SLAM and the OCLT tests as they are written. It seems you went to 10 before sundown, then added some more chlorine later but didn't retest to see where you started the night.

 

[Rmd0627]

The first add was after sundown, I retested, added more but no I did not retest until morning. It was at 3, it held all day yesterday and last night and is still at 3 as of right now. Is that an acceptable number since it is now holding? This is the first time in 3 weeks it has held anything

 

[ping]

The purpose of an OCLT is to rule out organics as the cause of FC loss. The water will only lose chlorine in two ways, from breaking down organics and from the sun. If you remove the sun from the equation, hence measure the FC at night and then again in the morning before the sun hits the water, this will give you the amount of FC loss due to organics in the water. If this lose is 1ppm or less then the water does not need a SLAM process to kill off the organics.