Chlorine depleting fast!

[TomS125]

I opened my 35,000 gal vinyl pool about 3 weeks ago. I converted to BBB after learning about pool chemistry from this site last season. I like knowing what is happening in my pool and not relying on someone caring more about making money off of me rather than caring for those who swim in it.

After getting the pool cleaned up (it is very clear now), I'm having problems with maintaining any chlorine level. I can get it up to 4ppm FC in the morning but it is at 0 in the evening. I did not have this trouble last year albeit with very high CYA levels (over 100). Now after several partial drains and refills, I have a more manageable CYA number (I thought it was ideal) but I can't believe that I can't hold chlorine levels for a day. My latest numbers are:

FC: 0
CC: 0
TC: 0 (I'll be adding more bleach once the sun is down)
pH: 7.2
Alk: 80
CYA: 40

I run sand filter 24/7 and there is very little organic material and no bather load right now. Like I said, water has looked good for past week and still not able to hold chlorine. I'm dumping about 3- 3.5 gallons a day to try to keep above 3ppm. That is not what I wanted after conversion to bleach.

Any thoughts?

[CarlD]

It sounds like you are still fighting something, but your testing is depleting the CC so it doesn't show.

My first suggestion is shock the h*** out of the pool...Run your FC all the way up to 15ppm and keep it there for several days...that should solve your problem. Trying to keep it at 3 with a CYA of 40 is, IMHO, pushing your luck. For that CYA, 3 is the MINIMUM FC you can run.

So shock it up, hold it there for a few days, then try running your maintenance level at 6ppm and see if your chlorine usage goes down. I know, I know--use MORE bleach????? Yup, I suspect that is exactly what you need to do to solve your problem.

Good luck!

[aylad]

Raise your CYA a little and see it that helps! That's why I run mine high...

Janet

[KurtV]

Tom,
Clearly something is amiss. My two theories are:

(1) Your CYA level isn't what you think it is (this seems fairly unlikely). How are you testing for it?

(2) Something is alive in there and is consuming your chlorine. If that's the case, shocking is the answer. Based on Ben's Best Guess Table (http://www.poolforum.com/pf2/showthread.php?t=365) you'll need to bring your free chlorine to 15 ppm until you can get it to hold some free chlorine overnight. It will take about 9 gallons of 6% bleach to get you to 15 ppm initially (that's a big pool). After that, test frequently and keep adding enough to bring it up to 15 ppm.

Best of luck.

[TomS125]

First, thanks to all of you for your help. Your dedication to us newbies just amazes me and is certainly appreciated.

KurtV, I have Ben's 234 test kit and have run the test 3 times already. It is hard to read but black dot seemed to completely disappear at the 40 mark both times. I learned of the whole CYA thing after taking over from previous owner and continuing with Tri-Chlor pucks. The refills have seemed to do their trick after being so high last July and having an algae bloom with CL levels where I had always had them.

I suspect it is working on something but the water is so clear right now that even that didn't seem to make sense. I can literally make out every screw head on the drain at the 8' deep end. Does it make sense to have that much for Cl to be working on with this water clarity? Also, when I measured Cl over last weekend, I found no CC with Ben's kit. It didn't seem to be the issue but UV didn't seem to add up either with CYA where it is at. I was thinking like Janet that I need to add it back now.

[KurtV]

First, thanks to all of you for your help. Your dedication to us newbies just amazes me and is certainly appreciated.

KurtV, I have Ben's 234 test kit and have run the test 3 times already. It is hard to read but black dot seemed to completely disappear at the 40 mark both times. I learned of the whole CYA thing after taking over from previous owner and continuing with Tri-Chlor pucks. The refills have seemed to do their trick after being so high last July and having an algae bloom with CL levels where I had always had them.
So, I think it's pretty safe to rule out that theory.

I suspect it is working on something but the water is so clear right now that even that didn't seem to make sense. I can literally make out every screw head on the drain at the 8' deep end. Does it make sense to have that much for Cl to be working on with this water clarity?
Not to me, but I can't think of anything else.

Also, when I measured Cl over last weekend, I found no CC with Ben's kit.
Yeah, the no CC argues against my second theory, but I don't think it rules it out.

...but UV didn't seem to add up either with CYA where it is at.
Agreed. UV can't be causing that much chlorine loss with that level of CYA (unless maybe you live at the equator).

I was thinking like Janet that I need to add it back now.
I'd really hesitate to raise CYA. Many people here are holding chlorine in their pools for a reasonable amount of time at even lower levels of CYA and you know better than I what a pain it is to get it back down. Where do you live, by the way?

I'd still give shocking a try (think Occam's razor).

[TomS125]

I'm in greater St. Louis area. We have just started to get some sun and warmer temps - not sure of water temp but imagine it is high 60's - still too cool for the kids!

Sounds like shocking is the answer to see if I can get it to begin holding.

[TomS125]

An update....I think my CYA measurement is off. Despite doing it twice and reading 40, I have to think it's more like 20. Chlorine is still disappearing fast but only during the day and I'm not showing any CC when I do have chlorine in there. After adding bleach and testing chlorine reading last night, it held the same reading this morning. Then it will be gone by the time I get home this evening.

I know I need to get more CYA in now but with the difficulty in knowing exactly where I'm at now, I'm not sure how much to add. I'm thinking about using pucks for a few days to try to maintain some consistent chlorine during the day while I'm at work and bring CYA up slowly until I see it holding. Thoughts?