CYA in a sock

[polyvue]

Polyvue,
A couple months ago I tried dissolving a couple cups of CYA granules in a gallon jug. Nope. Some did, most didn't. Kept pouring off the concentrated liquid into the skimmer and refilling and eventually after a couple weeks the solid was almost dissolved. Certainly didn't dissolve in 10 minutes. The granules are fine enough they will easily, or quickly, get past the skimmer and pump baskets. Once they make it to the filter how do you know how long they take to dissolve? I don't use the stuff personally. I smash up pucks.
Al

Well, my CYA is a bit low so I guess it's time I do an experiment. It's been my belief for some time that when CYA is added to my pool it can be detected in a fraction of the time suggested by those here and elsewhere... in hours, not days or weeks. But I'm conservative when adding chems and haven't tried to increase CYA 20 or 30 ppm all at once; perhaps I've been misled due to the imprecision of the test. The turbidity test doesn't exactly lend itself to the task.

And, even if the experiment supports my thinking (that all or nearly all of the CYA will be evident in testing within a few hours of application) I don't know how transferable this finding would be. Everyone's (IG) pool plumbing is a bit different, filter capacity, flow rates and head vary, etc.

So, I'll try to resolve this during the week, starting tomorrow night, by raising CYA 20 PPM. Got lots of melanine stored up. What the heck!

[waterbear]

Got lots of melanine stored up. What the heck!

err, melamine.

[CarlD]

I used to have a lot of melamine--but then we threw out my mom's 1950's unbreakable dishes....I hope they didn't get ground up and put into dog food!

[AnnaK]

My experience, for what it's worth:

Monday, 6/28, 06:30
ph 7.6
CYA 30 (consistent with previous tests over the past 4 weeks)

CYA goal 50. Per Pool Calculator, add 946 g CYA.

The CYA I use is mfg'd by Seaboard, 100% cyanuric acid, granular. I added 500 g slowly into the skimmer, basket removed, made sure all product was granules, no clumps. The 2-speed pump ran on 'high'. The CYA swirled in the pump pot for 15 - 20 minutes until it had all gone into the filter. At that point I set the pump to low and left it running.

According to the Pool Calculator, 500 g CYA in my pool would decrease pH by .2 and increase CYA by 11 ppm.

Tuesday, 6/29, 08:30:
pH 7.4
CYA 45

I can readily accept the difference in test results from the calculated expectation because a) the water volume can ever be just a close guess and b) variations in the 'endpoint' of the CYA test.

My past experiences with adding CYA product have been similar: it dissolves faster than what I had read and it's measurable within 24 hours.

[Watermom]

All this may be true for your pool. My experience has been that it takes longer for my pool to get up to the reading that I aim for when I add cya. So, although in some pools it may be in there and measureable fairly quickly, for some pools that doesn't always appear to be the case. Therefore, when I answer posts, I will still continue to advise people to wait awhile before testing again (to save reagents) or adding more. Better to be a little patient that overshoot a target of cya since it could mean a partial drain and refill.

Thanks for sharing!

[chem geek]

Personally, I've used an old T-shirt put into the skimmer and then added CYA on top of that shirt in the skimmer. It is important to note that my skimmer has a pipe going into the pool (looks like a return below the skimmer inlet) so that any skimmer clog will pull in water from the pool (and not crack the skimmer). I also have two floor drains so even if the skimmer and it's separate pipe to the pool were clogged, the pump would still be able to pull water from the floor drains.

So for me this works best as it is easy to do. The CYA dissolves in a matter of hours, usually overnight and certainly less than 24 hours. As for CYA measurement thereafter, at least 2/3rds of it registers after it dissolves (tested 24 hours after my last addition to the skimmer) and it could be more, but I don't usually add more than 20-30 ppm and target a CYA of 30-50 ppm so errors in measurement play a significant role here.

When CYA is added to the skimmer without a T-shirt, panty-hose, skimmer sock, etc. then it gets caught in the filter. The water velocity in the filter media itself is MUCH slower since it is spread over a much larger area. This is why it takes longer for the CYA to dissolve using this method. For my oversized cartridge filter with four 85 square foot filter cartridges, even with the pump at 48 GPM for my solar (it's 26 GPM with no solar), over 340 total square feet of cartridge area the water velocity is around 0.2 inches per second. In my skimmer (with no CYA in it that obviously blocks the flow significantly), assuming 15 GPM and a 1 foot diameter skimmer area the flow rate is about 2" per second.

Those that use a sock over the return should probably periodically squeeze the sock to break-up and mix-up the material inside. I think that a sock over the return is far better than simply broadcasting the CYA around the pool, but I think that putting the CYA into the skimmer either with a T-shirt/panty-hose/skimmer sock filter or without (to get caught in the filter) are very reasonable alternatives. Just make sure the filter isn't backwashed too soon -- the recommendation to wait a week should be fine (or if a CYA test shows that it is all dissolved).

Richard

[PoolDoc]

Hadn't thought about the water velocity thing -- makes sense.

Ben

[AnnaK]

All this may be true for your pool. My experience has been that it takes longer for my pool to get up to the reading that I aim for when I add cya. So, although in some pools it may be in there and measureable fairly quickly, for some pools that doesn't always appear to be the case.

You make a great point, Lisa: all pools are different. They are dynamic systems which change with the environment in which they live. Type of pool, type of equipment, fill water, use, weather, location, surroundings . . . the list is endless. As well, the way a pool is managed depends on the owner's knowledge, skill, understanding of pool water chemistry, attention to detail and so forth.

In the end, the goal we all strive for is to have well balanced water and that, ultimately, is the goal of this forum: to assist pool owners, via the sharing of experiences and observations by other pool owners, the coming together of myriad methods and techniques with the clear caveat that not everything works for everybody or every pool.

Thanks for helping me make that point.