CYA inaccuracy and slamming

[ouachita]

So I am in the process of slamming my pool and have been reading some other posts. I have ordered some CYA standard solution and was specifically reading posts about using it. It has been stated that a CYA tests accuracy is +/- 10 ppm. If that is correct then how does that affect a slam when the FC levels vary so widely? Using my CYA of 40 for example. The inaccuracy of +/- 10 ppm means that my SLAM FC could range between 12.2 and 19.8. For mustard algae the FC could range from 18.2 to 29.4 . What concerns me are 3 things:

1) Will the SLAM eventually work if the CYA is actually higher than what is measured?
2) Potential damage to the liner or equipment if CYA is lower than measured. This really bothers me with Mustard algae SLAM levels.
3) Swimming in above SLAM levels because of a lower CYA level than measured.

I'm sure these issues have been discussed. If so point me to existing threads. If not I would appreciate some input.

 

[Razorhog]

If you have a good test kit, learn the proper way to test CYA and trust your results. Everything else falls into place from there. Someone more knowledgeable will have to chime in on the potential for damage during mustard algae shock levels. It is my policy that no one swims while in the SLAM process, even if swimming at normal shock level is ok.

 

[ouachita]

I use the TF 100 fellow Razorback fan. But it's been stated that the CYA test has an accuracy of +/- 10 (even when done properly) which is what concerns me.

 

[jblizzle]

You should be fine to trust the test. You should not be at mustard shock level anyway.

 

[ouachita]

You should be fine to trust the test. You should not be at mustard shock level anyway.

I'm going to be at mustard shock level at some point because I have mustard algae.

 

[jblizzle]

Only for 24 hours.

 

[chem geek]

The recommendations for FC at a given CYA level have some conservative leeway built into them to account for CYA and other test errors. Not a lot of leeway, but some.

As for safety at SLAM levels, a regular SLAM has 10 times the active chlorine level as the minimum FC level so one day of a regular SLAM is like 10 days of normal chlorine levels. For a yellow/mustard SLAM it has 23 times the active chlorine level as the minimum FC level so one day of a yellow/mustard SLAM is like 23 days of normal chlorine levels.

Even so, a regular SLAM has the same active chlorine level as a pool with 0.6 ppm FC and no CYA while a yellow/mustard SLAM has the same active chlorine level as a pool with 1.4 ppm FC and no CYA. So basically it's no worse than what many commercial/public pools have when they don't use CYA such as indoor pools and some outdoor pools (say in New York where CYA is banned for such pools). Of course, it IS very harsh on swimsuits, skin, and hair and corrodes metal faster, oxidizes covers faster, creates disinfection by-products faster, etc. which is part of the reason people complain about many commercial/public pools.

 

[ouachita]

Thank you Chem Geek. I was hoping you would chime in. I always enjoy reading your posts.

 

[Swampwoman]

Ouachita, I have long pondered the exact same question re the +10 cya possibility...and this is why if a poster is lacking visible progress and is already filtering correctly, I'm given to recommend dosing slightly above "regular" slam level but below mustard level in a normal slam...with the goal of staying above the "correct" slam number at all times.

In your case, you will be spending 24 hours at mustard level, so that's a bit of a different duck as dsing above mustard level would be risky. But prior, during the normal part of the slam, dosing a bit higher to at all costs stay above your slam level will, IMHO, keep progress afoot without the stalls

Too many people fail to realize that every minute below slam level is a minute wasted, in which algae can outpace them Sustain-the-Maintain and you'll be golden!