Normal FC loss during day

[TCJ4]

Yesterday after noon i added 8oz of cal-hypo to raise my FC to 7 but just now i tested the FC and it's 1.5.

Is is to normal to lose that much FC during the day?

Pool gets alloooot of direct sunlight,from 7am to like 6pm

CYA :40

 

[Donldson]

It does seem a bit excessive, but if the sun is on it all day it could happen. Best way to find out if you have a problem is to perform an OCLT. If you lose more than 1 ppm overnight then you do have something that needs SLAMed in to submission.

 

[BoDarville]

The normal FC loss per day is somewhere between 2-3 ppm per day (24 hours) around this time of year. So your loss seems quite high at first glance. Was is over 24 hours since the prior chlorine dose?

To confirm if there is any organic contamination in the pool, you could run an OCLT.

Going forward, I would recommend dosing with chlorine in the early evening (after sunlight is no longer hitting the pool).

 

[TCJ4]

I chlorinate in the evening and i had checked FC yesterday and today in the early evening.

 

[TCJ4]

Just checked it again it's still 1.5 and CC is 0

 

[linen]

That seems like to much loss. I would follow the advice above, raise your FC to your SLAM level and do a OCLT.

 

[TCJ4]

Should i slam it tomorrow morning or in the evening?

Ps:im gonna slam it with cal hypo because i have allot of it and my CH is at 50

 

[linen]

Should i slam it tomorrow morning or in the evening?

Either is fine, as long as you wait 1 hour with the pump running after your last dose before you do the evening OCLT measurement.

Ps:im gonna slam it with cal hypo because i have allot of it and my CH is at 50

That is fine, but you may want to keep a log of what you are using...it can add up fast.

 

[TCJ4]

Just checked the part from pool school that said that if u have allot of direct sunlight u should keep the the CYA level higher,just wondering if that's the problem.

My current CYA is at 40.
Tomorrow gonna check everything again just to be sure.

 

[linen]

Do the OCLT first and see if you have organics...if you do then continue the SLAM process until that is done. If not, or when you finish the process, I would carefully bump up to 50 ppm cya (and maybe even a little higher for your climate).

 

[TCJ4]

I'm gonna go and check the FC level now.

I didn't add any chlorine since checking in the afternoon

 

[linen]

If you have the time you could do the OCLT tonight. Just make sure you give whatever chlorine you add an hour to mix before doing the evening test.

 

[TCJ4]

Just checked it the FC is 1ppm(dropped 0.5)

So in 7 hours it dropped 0.5ppm

CC:0

 

[TCJ4]

Did not add any chlorine

 

[scott.MI]

1ppm is not good, you need to add chlorine! Should never let it get below 3 per CYA chart. OCLT test or not you can't leave it at 1ppm

 

[TCJ4]

I will be adding chlorine tomorrow morning

 

[chem geek]

With 40 ppm you might normally see around 50-60% loss over 24 hours so from 7 to 2.8 or 3.5 ppm so getting to 1.5 which is a 79% loss seems excessive. The OCLT will tell you more; most likely you need to SLAM the pool to kill off nascent not-yet-visible algae growth. With your hot sunny area, a CYA of 50 ppm or more would make more sense. At 50 ppm you may lose about 40% over 24 hours and at 60 ppm a little less loss while at 80 ppm it may be around 22%, but such a high CYA becomes risky if you ever need to shock since it takes a lot more chlorine to get to the required shock FC level.

 

[TCJ4]

Just checked the water FC:1ppm
CC:0ppm

So i think i passed the OCLT,the water is still clear.

Do u guys recommend continue using 3" thrichlor because i stopped using them when my CYA was at 40.
I'm now using 65%Cal-Hypo.

Will post a full test result later

 

[Bama Rambler]

I wouldn't consider that a good OCLT. You should raise the FC to shock level and then run the test. 1 ppm FC is way too low for your pool anyway. You should have added FC as soon as you saw it was that low. Leaving it that low for any length of time is asking for trouble.

 

[TCJ4]

I will add some cal hypo now just to raise the FC to 5 and in the evening raising it to shock level and doing the OCLT again.