CYA loss from Texas rain

[vcarnett]

Split by moderator from HERE. jblizzle

Hey I'm having same problem. Scratching my head here in Austin. I had drained 40% of my pool due to really high cya (ignorant puck user pre-TFP). This reduced cya to 40 and all else was good (CH a bit low @ 140) until today (1 week later) when I just measured -40 after only 1.5" of rain! Water is clear. wth is going on? I tested twice thinking that surely I had screwed up. That's a huge drop in a week!

Test results from 6-16-15 after big rain (over an inch)

FC 0 (added 2 bottles bleach, 96oz ea of 8.25%). Now ~0.4

CC 0

pH 7.5

TA 50

CH 140

CYA -40 (was 40ppm just 5 days ago)

Water crystal clear - running pump 6 hrs / day with very good circ

Perplexed in Austin

 

[Texas Splash]

You might like to see this thread about rain and CYA loss: Question regarding CYA and rain storms.

 

[tim5055]

CYA doesn't go lower than 0 (zero), how do you get -40?

 

[JVTrain]

Your pool is 17,000 gallons. 1.5" of rain in your size pool would be about... 400 gallons at the most. That's just over 2% water difference. You can see why most experts here would say even large amounts of rain will have a minimum effect on water chemistry.

 

[vcarnett]

oh, duh... Just looked at my taylor tube again. the "-" next to the 30 is smaller than the rest so I read as -30 (neg). I understand now that it's just 30. Anyway, I'm filling the tube all the way and still clearly see the dot so I'm assuming that would be 0.

Still not understanding the dramatic drop (40 - 0) in 5 days.. In the meantime, I've added 4, 3" pucks to my skimmer basket to start getting that up. I'll definitely discontinue those once things are back to normal.

Thanks all

p.s. thanks, Splash, I'll have a look at that link

 

[vcarnett]

Just added ~4lbs Baking Soda to raise TA. Left the pump running and will test in the morning.

Still scratching head over the big drop in CYA (45 - 0) in 5 days. Besides adding the 4 pucks to skimmer, I added 7 (all I had on hand) to the in-line holder (I understand the pucks will not quickly raise CYA, so will take further action on that tomorrow as necessary).

 

[Scuba_Steve]

So you added 192oz of bleach and tested shortly after and your FC was only 0.4?

Do this, add enough bleach to theoretically bring your pool up to 10ppm. Test in 30 minutes. Report your results.

 

[vcarnett]

Sorry, it was 0.6 after 192oz. Strange. OK, will test tomorrow morning and then add accordingly (going by poolmath calc) to bring to 10 and report back. Thanks

 

[vcarnett]

OK things are looking better

Added ~4lbs Baking Soda last night and 1 gal 8.25% bleach this morning (meant to get enough to theoretically bring to 10ppm, but wasn't thinking and bought only 1 gal). Tested after a couple hours circ.

FC 5.2 (keep in mind that I also have 4 Leslie's pucks in skimmer bask and 7 in in-line holder since yesterday- in attempt to bring up cya)

Ph 7.5

Ta 80 (added ~4lbs baking soda yesterday to bring up from 50 - looking good)

CH 120 (has dropped - surely due to rain - will get this up)

Cya 30 (I think it's actually just a tad lower, but definitely up from 0). Still perplexed over what's going on here. Did use new 0013 reagent just bought today (same brand - Taylor). However, what I used for all previous tests was only a few weeks old and stored indoors.

CC 0

I'm wondering: I've been using cheap, $1 (from Mexico) HEB brand bleach (96oz). Today I used Clorox brand (1 gal). However, they both claim 8.25%. I'm hoping to continue using cheap brand as it's ~ 1/3 price (considering vol diff)

p.s. I also tested my tap. (n/a to this post, but I'd been meaning to do it): CH 50 and pH ~9

 

[Texas Splash]

The HEB "Bravo" bleach is fine. That's what I use.

As for the FC ... because there was a concern for your FC dropping very quickly, I "think" Scuba Steve was looking for ammonia in the water (he may chime-in later and confirm). Here's an example why from a previous thread: "If you do have ammonia in the pool the FC won't register - it's consumed almost instantly, and the CC is high. The solution is more chlorine - but if you want to confirm ammonia you can purchase an ammonia test kit from a pet supply store (its for fish tanks)."

How is your water looking today?

 

[rphpool]

I use the cheap HEB 1 gallon brand because the store sales alot ( big turn over ) so it seems it should be fresh. I wonder if there is a test we can do to determine the strength???

 

[vcarnett]

Ok good to know i can continue to use cheap stuff.

Fc was registering, though low. CC is 0. Fc good today at 5.2. I will test tomorrow morning for fc loss. Water looks fantastic. Thanks for replies.