Increased combined chlorine despite low overall chlorine consumption

[Wake9909]

Hi guys!! Thanks for all the wealth of great info on this site. My pool has been in virtually immaculate condition for the three summers we’ve had it now. My husband and I have been completely managing it on our own with the help of Trouble Free Pools!

That being said, I now have a question. We have a plaster pool with a salt water generator. We run our pool pump 24/7 at 2500 rpm during the summer months. Our SWG is currently running at 25-30%. My most recent chlorine level was 7.5 ppm with a CYA of 70 (checked yesterday). I noticed the past couple of drop tests I’ve done (I usually check about every other day or so), the combined chlorine is now around 1 ppm. It’s historically always been 0.5 ppm or less. It just now creeped up recently. The water still looks crystal clear, the free chlorine level is not being consumed…it lingers around 6-7 most all the time. All other things seemingly in good, normal working order, is it necessary to SLAM our pool, bringing it to a level of 28 ppm just to decrease the CC by 0.5? Or can I perhaps just add another gallon or 2 of 7.5% bleach to give it a chlorine boost? Thoughts?

 

[Mdragger88]

To rule out testing interference try cleaning your beaker with alcohol.
Next,
do u cover the pool? If so try leaving the cover off a while before testing for trapped cc’s to escape.
Had any kiddos or a party in the pool? If so maybe it’s just lingering bather waste & a little extra fc will do the trick.
To rule out an organics problem do an Overnight Chlorine Loss Test.
Sometimes an oversized swg can kind of hide a nascent algae issue (your swg size isn’t listed in your signature)

 

[pjt]

We run our pool pump 24/7 at 2500 rpm

Why are you operating at a fast speed? You can probably lower your RPM (and electricity bill) considerably and still achieve your goals.

Taylor K-2005 test kit

Confirm you also have a FAS-DPD test kit?

 

[HermanTX]

I would retest again - maybe in morning then in afternoon to check your CC. If still at 1 or higher, then do a Overnight Chlorine Loss Test to verify. Remember to turn off SWCG.

I am curious why you are running your VS pump at 2500rpm 24/7. Pump speed does not affect SWCG generation. Have you tried to lower your pump speed to verify your SWCG still operates? Most run a SWCG at minimal speed + 200rpm to ensure the flow switch is activated. Then ramp up to higher speeds for skimming or if you need to run a cleaner.

 

[Wake9909]

To rule out testing interference try cleaning your beaker with alcohol.
Next,
do u cover the pool? If so try leaving the cover off a while before testing for trapped cc’s to escape.
Had any kiddos or a party in the pool? If so maybe it’s just lingering bather waste & a little extra fc will do the trick.
To rule out an organics problem do an Overnight Chlorine Loss Test.
Sometimes an oversized swg can kind of hide a nascent algae issue (your swg size isn’t listed in your signature)

Oh, good idea. I have not cleaned out my beaker and honestly haven’t even thought about it till now. I’ll bet that’s probably what the issue is.

We do not cover the pool. And it is in full sun most all of the day. I think our SWG is a Pentair IC-40. I’ll update my signature with that. I guess I thought I already had.

We did have a pool party a couple of weekends ago and are actually planning on another one this upcoming Labor Day weekend. It could be residual organics, I guess. I will say the water still looks pristine and I net it out every day, vacuum it several times a week, and empty skimmers almost every day. Perhaps just adding an additional gallon or two of bleach will set it straight again. But, I’ll do what you suggested, first. I’ll clean out the beaker with alcohol and re-test first. Thank you!!

 

[Wake9909]

Why are you operating at a fast speed? You can probably lower your RPM (and electricity bill) considerably and still achieve your goals.


Confirm you also have a FAS-DPD test kit?

I do.

 

[pjt]

I do.

Excellent. When you update your signature, you can include that info.

 

[Wake9909]

I would retest again - maybe in morning then in afternoon to check your CC. If still at 1 or higher, then do a Overnight Chlorine Loss Test to verify. Remember to turn off SWCG.

I am curious why you are running your VS pump at 2500rpm 24/7. Pump speed does not affect SWCG generation. Have you tried to lower your pump speed to verify your SWCG still operates? Most run a SWCG at minimal speed + 200rpm to ensure the flow switch is activated. Then ramp up to higher speeds for skimming or if you need to run a

To rule out testing interference try cleaning your beaker with alcohol.
Next,
do u cover the pool? If so try leaving the cover off a while before testing for trapped cc’s to escape.
Had any kiddos or a party in the pool? If so maybe it’s just lingering bather waste & a little extra fc will do the trick.
To rule out an organics problem do an Overnight Chlorine Loss Test.
Sometimes an oversized swg can kind of hide a nascent algae issue (your swg size isn’t listed in your signature)

Well, you were right. It was the dirty beaker that needed to be cleaned out. Combined chlorine came down to 0.5 ppm after that. I got an Amazon and ordered a new one. It’s time. I’m hoping with the brand new beaker, my CC will be zero! Thank you so much! You saved me $$$ to not have to buy a bunch of bleach and a huge headache, too!

 

[Mdragger88]

Well, you were right. It was the dirty beaker that needed to be cleaned out. Combined chlorine came down to 0.5 ppm after that. I got an Amazon and ordered a new one. It’s time. I’m hoping with the brand new beaker, my CC will be zero! Thank you so much! You saved me $$$ to not have to buy a bunch of bleach and a huge headache, too!

Glad that’s sorted out
Mine gets stained & that’s my little reminder to clean it. When i got my new one it was amazingly clear & i was embarrassed that i had been using the old one the way it was for so many years it’s literally like $2

 

[Wake9909]

Glad that’s sorted out
Mine gets stained & that’s my little reminder to clean it. When i got my new one it was amazingly clear & i was embarrassed that i had been using the old one the way it was for so many years it’s literally like $2

Ha ha!! Me, too!! Yeah, I’ve been using the same one for over 2 years…and have never cleaned it. I have always just rinsed it out. Oops. Well, now I know!

 

[proavia]

What is the minimum speed you could run your pump and still get the SWG flow switch to close.
With a clean filter, add about 200 rpm to that minimum to close the flow switch will allow for the filter getting dirty and still keep the SWG running.
Chances are it's probably less than 2500 rpm and if you were to lower the rpm, you could save money on electricity.