Cyanuric Acid (CYA) Drain High or Low

[LynnB]

First I'd like to say hello to everyone, and I'm really excited I found this site (I'll be ordering a TF100 test kit soon). Last fall we finally bought a house with a pool and have been looking at it every day since, just waiting for it to be warm enough to actually enjoy. The pool was built in the 80's and replastered about 6 years ago. We've been having the water test off and on the last few months at the local pool store chain. A few months ago they said our CYA was over 100 and we needed to drain about 1/3 of our water out and replace. We did this and CYA reading came down to around 90. After having another test done yesturday we were told CYA was to high again and that we needed to do another drain and fill, but as we drain the water we should brush the sides with a solution of 1 part muratic acid to 2 parts water, and that since we hadn't done this the first time, that is why our levels are high again so soon. So here are my questions:

1. Should I do the acid scrub/brushing on the pool walls as I drain?

2. I've read mixed reports that the cya tends to float to the top or sink to the bottom. Which is true? The reason I'm curious is it seems where it sits in the water would be the best place to drain from, so if it sinks, using the main would work best, if it floats, then renting a sump pump and placing it on the stairs might be the better option. Am I over thinking this?

Any help is much appreciated.

Thanks,
Lynn

 

[loughps]

Once dissolved, CYA is basically spread evenly through your water, where you drain from will make no difference.

The most likely reason your CYA only went down to 90 was that with most CYA tests, 100 is the maximum reading. Anything over 100 will still read as 100. I'd continue to drain and fill and test until your CYA number is within range.

I don't have a plaster pool, so I'll let others weigh in on the acid scrubbing, but I'm pretty sure you're going to hear that it has nothing to do with the CYA reading. Whether it's a good practice or not, someone with knowledge will say soon enough.

Get that test kit ordered so you can do your own testing as soon as you can. You'll be really happy you did.

Welcome and good luck.

-- Pete

 

[JasonLion]

Scrubbing the walls of the pool with an acid mixture will take off a thin layer of plaster and shorten the lifetime of the remaining plaster. There are some situations where you might want to do that, especially calcium scale buildup, but it won't have any effect on CYA one way or the other.

 

[LynnB]

Thanks for the responses. I was a little concerned about the acid wash, that one just didn't make sense to me. Guess I'll just drain a little more this time.

This is a great site.