How fast can CYA lower without a drain/refill

[PoolUmp]

Hey all! So, my pool has been consuming FC like crazy recently, to the tune of 4-5 PPM each day! Last season my CYA was around 80, but due to severe water constraints here in CA I was not able to drain and refill. SO, I bit the bullet and used a lot of bleach. In my last few CYA tests I have Ben getting readings around 55. Does that seem like a realistic drop in CYA in that time span? And do you think my FC consumption could be that high due to lower CYA. Temperature here is over 110 for the next week. I'll be doing a OCLT tonight, but here are my last test results:

FC-8
CYA-55
CC-0
TA-120
CH-260

Thank you!

 

[mknauss]

If you were at CYA of 80 last year, and you are now at 60 (round up) and you have a sand filter you backwash occasionally, and you have not added any CYA via stabilized chlorine, then yes, it could have dropped from 80 to 60 in that time frame.

Once you do your OCLT it will tell you if you have organics or if it is FC consumption due to sunshine, which is at its peak right now.

Take care.

 

[Richard320]

You probably got 1/3 of your pool depth in rain this year, didn't you? That'll dilute things. I count on it to lower my CH. I even aimed the gutter downspout at the pool to get as much CH & CYA -free water as possible.

Still, even with the heat, 4-5 FC per day seems a little high. I suggest Overnight Chlorine Loss Test

 

[PoolUmp]

Thank you, yes, doing OCLT tonight. Additionally, I have this giant purple flower tree that hangs over the pool, and drops copious amounts of detritus in the pool each night...will this potentially compromise my OCLT? Sorry, there's more...at night I can see a lot of little particles in the water near the light. Is this just life with a sand filter? Unless I use DE or CF?

 

[duraleigh]

The particles at night is just life with a pool......not sand, DE or cartridge. You will get visible particles at night regardless of your filter type.

What does your water look like?

 

[PoolUmp]

Ok, so my OCLT failed...lost 3PPM over night, although I must admit, my testing at night yielded several different results, so I'm not so sure. But, I lost 10 PPM FC during the day today, so I'm just going to start a SLAM. My hope is that considering I already pass 2/3 of the tests, my SLAM should be fairly quick. Is this safe to assume?

- - - Updated - - -

Water looks great. Clear as can be

- - - Updated - - -

Additionally, do you think lots of flower petals could eat up that much FC? I literally have to skim the pool 3X a day (I will be trimming them back VERY shortly!)

 

[PoolUmp]

Ok, well, here we go. I passed the OCLT last night. Brought FC level up to 24.5 last night. 6AM this morning, still 24.5! So....could it have been that easy to knock out whatever was there? We'll see how much FC we burn through today. I'm moderately confused at this point. Water is clear, CC 0-0.5. So I'll let FC drop over the next few days

 

[Richard320]

Ok, well, here we go. I passed the OCLT last night. Brought FC level up to 24.5 last night. 6AM this morning, still 24.5! So....could it have been that easy to knock out whatever was there? We'll see how much FC we burn through today. I'm moderately confused at this point. Water is clear, CC 0-0.5. So I'll let FC drop over the next few days

It's quite possible if you get it fast enough. If you had to wait a week to take a sample to the pool store to catch that it was using FC so fast, it would have gone from being thirsty to being green most likely.

 

[PoolUmp]

Now I'm at a complete loss! I passed my OCLT, had FC 24.5 last night 11 PM, and same this morning around 6 AM. Water is clear as can be, and CC is at zero. It's now 1:30 PM, and my FC is reading 12.5. What is going on!!??? I've been running my pump since yesterday. Could the vegetation really eat up that much FC? Skimmer was packed with flower pedals. Please help!

 

[PoolUmp]

Ok, I looked through some old posts, and found some info. Please confirm: the higher my FC, the faster the sun/heat will eat it up. Thus, as my FC normalizes (out of SLAM levels), FC loss should slow?

 

[borjis]

ya it drops down rapidly when it's much higher than target levels.

 

[Razorhog]

Ok, I looked through some old posts, and found some info. Please confirm: the higher my FC, the faster the sun/heat will eat it up. Thus, as my FC normalizes (out of SLAM levels), FC loss should slow?

Yes. From what I understand, shock level FC will fall faster. I'm in the same boat right now.

 

[Richard320]

Now I'm at a complete loss! I passed my OCLT, had FC 24.5 last night 11 PM, and same this morning around 6 AM. Water is clear as can be, and CC is at zero. It's now 1:30 PM, and my FC is reading 12.5. What is going on!!??? I've been running my pump since yesterday. Could the vegetation really eat up that much FC? Skimmer was packed with flower pedals. Please help!

That loss seems about right. You lost half in 6 hours. That's why you can't just add a week's worth at once and walk away for a week.

 

[PoolUmp]

Nice chart! Thank you! Explains a lot... essentially going to lose 1/2 every 6 hours, regardless of initial FC. Right? So if I start the day with 10, I'll end the daylight hours with 2.5, assuming no or minimal organics