Testing CYA - Just venting...

[rodrigo]

I am beside myself with measuring CYA.

I am still getting the hang of drop based testing (the TF100, natch), after years of strips. FC, CC, T/A, CH. No problem. However, the CYA test has me pulling my hair out. Over the last two weeks, I've measured CYA at values ranging from 65 to over 100. I'm already into my reagent refills. Ugh. I've tried many of the tips I picked up from searching the forums: pour the sample back into the mixing bottle to measure again, wiggle the bottom of the tube to be sure the detect the dot's motion, do the test outdoors in indirect daylight... {sigh} I just don't feel confident that I REALLY know how much CYA is in there.

My water is 98% cleared up after nearly a week at shock level, but it still looks dull. I'm wondering if my CYA really is around 100, and therefore I wasn't really shocking the way I thought I was. I'm considering a 20% dump and refill (to get from 100 to 80 ppm CYA), which I figure is about a 10" drop in water level based on my fiberglass pool dimensions. Is this safe to do in one fell swoop? I don't believe my water table is particularly high at my house (my sump pump rarely runs, unless there are recent, heavy rains).

I'm TRYING... I really am... sheesh.

 

[reebok]

can you get it tested at a pool store? if they say it's 80, measure yours at 80 and see if it's similar. yours would be a good case for that known cya test, where you buy a solution that has a known amount of cya and test it to make yourself familiar.

 

[JasonLion]

Proper lighting is important for the CYA test. You want to test on a sunny day but keep the view tube in the shade. Taylor recommends standing in the sun with your back to the sun and the view tube in the shade of your body.

Other than that, try it a number of times with a sample that you use over and over again, it should be good for at least five minutes, and see if you can get repeatable results.

The CYA measurement is never exact. If you get results that are all within 10 of each other then you are doing well.

 

[rodrigo]

Well, this last test (yesterday) was definitely a sunny day, though it was nearing evening -- maybe around 6:00 pm? it was still broad daylight, though; bright & clear out. I repeated the test several times (poured the solution back into the dropper bottle), and received a virtually identical reading each time. Prior tests were done closer to mid-day, I guess, but as you described, Jason: I held the tube in my shadow at waist level, with my back to the sun. And I have gotten levels of 65 to 80 the last two or three times I tested. Looking at it now, I guess the ambient light level was certainly lower for the the most recent test than for prior ones.

I'm trying to get this shocking worked out, so I can start the process of lowering my T/A, which is very high right now, around 150. Again, I wonder if I haven't *really* been shocking, due to underestimating how much CYA is present.

Unfortunately, the only pool store in town that I kinda trusted recently closed. There is one other guy here, about whom I've never heard a single good thing. I DID discover a place in town that is more of a supplier to public pools & swim teams. Most of their sales are internet & mail order. They have good prices on Taylor reagents & such, but they do not do water testing in their retail space.

 

[duraleigh]

You might be trying to narrow it down a little too much, If you get repeatable results between 65-80ppm, I'd call that 70 and take the next step.

With an SWG, that next step for me would be to drain and refill until I got the CYA down around 50ppm

The CYA is always +- 10ppm so your testing sounds fairly close to what most of us experience

 

[JasonLion]

With a SWG, the recommended CYA level is between 70 and 80, so CYA is good where it is. There isn't any need to lower CYA.

 

[anonapersona]

I find that handing the vial to my spouse helps. "I can see it clearly!" hands it back, "Uh, yeah, I guess I do too." I agree and add a few drops and it is exactly what I measured weeks ago.

 

[duraleigh]

There isn't any need to lower CYA.

Oops! I was too lazy to look further back up the thread to check for an SWG and meant to type "without an SWG," Very slack on my part, Rodrigo....sorry for creating unnecessary confusion.

 

[rodrigo]

I'm feeling a little better now -- at least with respect to testing CYA. I did another test today as soon as I got home from work, a couple of hours earlier than the last one. I got repeated readings of 70 - 80 over the course of two or three minutes.

With that out of mind (for now), I think I need to get back to shocking. My wife thinks the water is pretty clear, but I just don't think it sparkles like it should. It seems just a bit... dull. I DO still get CC readings of .5, and my last overnight test had a FC decrease of 1ppm. I know this is within 'spec', but wonder if maybe I was running my shock level just a bit low to really clear things up. I brushed the pool tonight, something I haven't done for quite some time , and will put the baracuda in in the morning. Maybe that will help...

You folks really do a wonderful thing here. I surely do appreciate the support.

 

[frustratedpoolmom]

The dullness can be attributed to lack of brushing, I don't think you need to keep shocking, but you can keep the levels elevated for a few days if you like. Just keep the filter running, brush, and it will sparkle.