CYA Good or Evil?

[jbsmith22]

Hi folks,

First time pool owner, bought a house with an 18x36 IG pool, opened it up a couple weeks ago and have been reading here voraciously to try to understand pool chemistry. Sheesh when my dad owned a pool, all we did was dump a couple coffee cans of liquid chlorine in every few days, who knew it could be so complicated!?!

Anyway, I have a question about Cyanuric Acid. It seems (from reading the board) that people are all trying to either add it or get rid of it. I THINK I understand why - not having any means your free chlorine gets eaten like crazy, having too much means you can't get any free chlorine. I seem to have a different problem (or maybe it's not a problem, hence my question).

When I first opened the pool, there was no chlorine. I had shocked a couple times over the winter per the previous owner's suggestion and the water was crystal clear at open, but the numbers were bad. After mucking for awhile I was at FC of 0.04, TC of 0.06, CYA above the meter's ability to read. So I read more and mucked more and I seem to have settled in to the following numbers (it has drifted slightly over the past week or so, but not much):
FC: Above the meter's ability to read (>10ppm). I am testing three ways - I bought a ColorQ 7 Plus because my color matching skills are pretty weak and also with test strips and a standard (simple) drop kit. I'll be ordering one of the TFP test kits tomorrow. All three show FC and TC above range.
TC: Above the meter's ability to read.
pH: 7.4 (pretty steady - 7.5 3 days ago, 7.2 6 days ago)
TA: 151 (this one seems to fluctuate - it as 115 three days ago and 128 three days before that)
CH: 81 (increasing - 75 3 days ago, 69 6 days ago)
CYA: 110 (fluctuating - 91 3 days ago, 115 6 days ago)

I haven't put any chemicals in for the past 6 days.

The water is crystal clear, there is no smell, and there is light sediment on the bottom (I vacuumed the other day, nothing since).

I should also note that the pool has a slow dissolve chlorine tablet thing coming off the filter and I put some tri-chlor sticks in it when I first opened the pool. They are now gone and I haven't put any more in since it seems tri-chlor adds CYA. So I'm using liquid chlorine exclusively, though, again, I haven't put any in in nearly a week.

So my question is: Do I have a problem? I am going to try the "test 1/5 the sample and multiply by 5" trick to get a better idea of the actual FC/TC numbers tomorrow, but should I be concerned? I saw in one post where having 10-11% of CYA means that there is "enough" FC to do the job and I also read that there is no "safe maximum" for FC so having 10 ppm for a CYA of 100 should mean that it is safely protected from bacteria/algae and also safe to swim in. Other than the presumed difficulty of keeping the FC that high (a problem I do not, for some reason, seem to be having) is there anything inherently "bad" with having a 100/10 ratio instead of the more normal 40/4 ratio? I'd sure as heck like to avoid draining 10k gallons of water into my backyard if I don't need to, but obviously I don't want my kids swimming in an unsafe pool.

Any advice/guidance is very welcome. This is a great board and I already ponied up my money to support it

Jason

 

[duraleigh]

Welcome to the forum. :lol:

Do I have a problem?

Well, sort of, I think you are overcomplicating a bit but let's get started......

How does your water look?

Have you read "The ABC's of Pool Water Chemistry" up in Pool School?

 

[Isaac-1]

Welcome, and to answer your question, I think you have a fairly good grasp on it, and your testing numbers show part of the reason we don't tend to like the Color Q, the resolution gives a false sense of accuracy, and its range is really not all that good on some of the test that matters. As to if you have a problem or not, we will see when you get your test kit in and can do an OCLT pool-school/overnight_fc_test]Overnight FC Loss Test This will tell us if you have a low level algae problem trying to take hold. If not then your good to go, at least for now, but you should work on slowly getting that CYA down through water replacement, and stop using stabilized Chlorine, because if your FC to CYA level ever dips, or if you just get unlucky and some type of algae ever does start growing in your pool then it will be practically impossible to defeat it without major water replacement.

Ike

 

[BoDarville]

jbsmith22:

Welcome to TFP

This is a great board and I already ponied up my money to support it

Thank you for doing that.

+1 That your current test products are a big part of the reason for the fluctuations.

I'll be ordering one of the TFP test kits tomorrow.

I would make ordering this Job 1. Once it arrives, let's baseline your pool's chemistry using the TF-100 and then use that going forward.

 

[jbsmith22]

Thanks for the quick replies everyone!

A few answers:

How does your water look?

Sparkling crystal clear, no smell, no (visible) algae, basically looks and feels perfect.

Have you read "The ABC's of Pool Water Chemistry" up in Pool School?

A couple of times -- the first pass just made my head hurt.

we don't tend to like the Color Q

I know most people prefer dropper tests, and I've been doing three different tests each time (dropper, strip, and Color Q) just to confirm and to look for trends. For instance, when I first opened it, FC was 0, now it's off the scale on all three tests, so accuracy is a concern but I think I can trust the general trend. That said, the "good" test kit is ordered so hopefully it'll be here soon.

If not then your good to go, at least for now

In the meantime it seems like it's okay to use the pool so long as I keep an eye on it.

you should work on slowly getting that CYA down through water replacement, and stop using stabilized Chlorine

Check on both counts. Sticking with liquid chlorine only for now, no more tabs and I'll start draining it a bit at a time and refilling with hose water. (Giving time between for the water to circulate so I'm not just draining the top water over and over)

I would make ordering this Job 1. Once it arrives, let's baseline your pool's chemistry using the TF-100 and then use that going forward.

Okay, so as soon as the kit gets in, I'll do the tests and post the results.

Thanks again!
Jason

 

[duraleigh]

Sounds like you are in pretty good shape with a crystal clear pool, CYA too high but going to work on that and, lastly FC up around the 10 ppm range because your CYA is so high.

If it's warm enough, I'd go swimming!!