Cyanuric acid missing

I have started up my pool for the spring. Opened to a green mess. After about 70 gals of bleach (30k gal + vinyl in ground), I have apparently held chlorine overnight. My question is I tested at zero cya at opening (I am sure it was eaten by bact.). Normally I keep at 50+ ppm due to living in the deep south. I have started adding cya with 2 socks with 3 lbs each at each skimmer entrance. My question is (finally I know) Is it ok to add bleach in the deep end with the cya at the sides? Oh yea ph is 8 to 8.5, alk. is 90. Thanks, been using the bbb method for 3 seasons and it was the best thing I have every done for my pool.

Hi, glad to see you back!! Yes, it's fine to add bleach at the deep end with the CYA at the sides, just don't put them into direct contact with each other. You need to get the pH down below 8, though. Low chlorine, low CYA and high pH are ideal conditions to use trichlor, if you're tired of hauling bleach:)

yes good idea, Everybody at Sams probably thinks I am building bombs or something

Janet,
I just checked my ph and is was probably over 8. I went ahead and added some acid, how long do you think I need to wait to retest. Also I was going to retest about dark and add bleach to get me to about 8 or 9 ppm. Does this seem like a good idea.

I'm not Janet but ............You can retest pH after 3 hours or so. Give the acid plenty of time to mix in well. Yes to adding more bleach this evening.

Watermom,
Sorry I thought Janet had answered my first question but thanks for the reply. Will retest tonight.
Thanks

It was Janet. But, she and I bounce in and out of the threads without worrying about 'whose' thread it is.

Just want to confirm:

+ 30K gal pool
+ 50+ CYA in fall
+ 0 CYA when opened
+ 70 gallons of 6% bleach to achieve chlorine retention overnight (140 ppm chlorine dose!)

Are those statements correct?

Sounds like bacterial conversion of CYA into ammonia as happened to me and that I describe in this thread (this post has a summary of chlorine usage before I got a reading and is described technically in this post). For every 10 ppm CYA degraded it would take at least 25 ppm and possibly 32 ppm chlorine to get rid of it. So 50 ppm CYA could take 125-160 ppm chlorine and that's not counting what is needed to get rid of any algae.

The best way to minimize the likelihood of this happening or of opening a pool to algae is to close the pool when the water is cold (below 60ºF and preferably below 50ºF) and to open the pool early before it warms up (so before it hits 50ºF or 60ºF). Of course, if one can maintain chlorine in the pool over the winter, that will work but isn't viable for pools that are closed due to freezing.

Ben
I would be happy to give you the exact numbers. First it has been 14 days this morning since I started my pump for the season. I closed in later November when it was in the 40's. I took fc to shock level @ 15ppm, ph @ 7.8, ta @ 100, and cya 50ppm. I let it circulate 1 day and pulled pump. I do not cover pool just winterize and leave uncovered. Living in the deep south this year we had almost no winter with temp at times in the 80's and easily the 60's at night. When I opened 2 weeks ago I had 0 cya, 0 fc, and ph was high at well over 8ppm. I have added to date 72.5 gals of 6% bleach, 9 lbs cya, and 12 pounds of baking soda, oh yea 120 lbs of salt ( I do not have a swg but run about 2000 ppm salt for feel). I just tested about 15 minutes ago and here are the numbers. fc=9, cc=0, ph=7.3, cya=40ppm, ta=120, and salt=2290. It is a 20*40 vinyl inground pool with a sand filter. If my math is right it should be in the 30 to 32000 gal range. This is the third season I have used your method and it is wonderful. My maintenance last year for example was about a 1.5 gals of bleach a day, and that was all. What is your opinion of swg's. I have no problem with adding bleach but if there is something a little more maintenance free I am all about it. I just have not been able to justify $1000 for a swg. Is the money savings and time savings really there? My pool is pretty easy to maintain (once I do my due work for a couple of weeks early in the year). It cost me about 40 gals of bleach a month or about $85 dollars. And time wise less than 2 hrs a week including testing and adding bleach. Any input would be appreciated. Thanks again

Wow.

36K gallon pool (3.34 pool factor)

Initial:
pH = 7.8
TA = 100
CYA = 50

Startup:
pH = 8.0+
TA = ?
CYA = 0

Cleanup:
+ 72.5 gallons of bleach (3.34 * 72.5 * 0.51 =) 123 ppm chlorine (72.5 x $2.50? = ~$180?)
[ very close to Chem_Geek's estimate of 2.5+ ppm of chlorine per ppm of CYA degraded ]
+ 9 lb CYA ( 9 * 3.34 = ) 30 ppm
+ 12 lbs soda

Operations:
40 gal bleach / month => 0.51*40*3.34 = 68 ppm/month or about 2 ppm/day
(a little high, I think)

update
+4lbs baking soda
+3lbs cya
+6 boxes of borax (24lbs I think)
+5 gal acid (borax & acid for borates)
+480 lbs salt
installed a SGS sg3000 swcg

As of 6:00 am this morning
fc=4.0, cc=0, ph=7.0, alk=70, cya=70, salt 4200
aerating water to raise ph as I am waiting on Borate test strips to be delivered. There is one strange thing my cya is testing at 60 to 70ppm but I have only added enough cya to raise to 40ppm. It was testing at zero 6 days after opening pool. First week of opening I didn't add anything but bleach. Water this morning is absolutely crystal clear (the addition of the borates WOW!)

While you wait for PoolDoc to answer your swcg question with more authority, I thought I'd share my experience since you were asking.

IMO, a swcg won't really save you any money, since you have to pay so much up front. Also, you have to regularly add muriatic acid to the pool and periodically (maybe once a quarter for me) add some additional salt due to splashout, and maintain a fairly high CYA level (sounds like you already do that, though). What it does do is saves me time. Once I got the output pretty much dialed in, my chlorine level is just nothing to worry about. I clean the pool, test the water pretty frequently but I hardly ever add anything other than the things I mentioned above. Basically, I love my swcg. It came with the house/pool when I bought it, but was not functioning until I replaced the control board. I greatly prefer adding acid weekly (actually every 2-3 weeks now that I added borates) instead of adding chlorine daily.

Also things like a week or so on vacation become much less stressful with regards to your pool. I just came back from a week and a half road trip to Nashville, TN. Came home to a clear pool with leaves in it, but the chemical levels were all still right were I wanted them and it was a matter of scooping out the stuff that had blown in.

One important thing to consider with a swcg is if you have any metals in or around your pool. If they're not treated for salt water, they will corrode. This includes heaters. Also, if your pool is still under warranty you should check to see that salt water wouldn't void your warranty.

kelemvor thanks for the info, the money for me is not as big of an issue as time. I am trying to get my swcg dialed in now. I am trying different run times and percentages right now. My goal was to hopefully have everything squared away by May 1. Hope you had a good time in Nashville, I just got back myself. My son was taking some classes at Vanderbilt. Very nice campus and community.

Hi Smile;

Just commenting here on the expected vs actual CYA levels. There's a good chance your pool is not 36,000 gallons. It's visible on Google Maps, and looks like standard rectangle liner pool with 4' radius corners, 3.5' WATER depth in the shallow end and maybe a 9' hopper. Keep in mind, builders and liner makers tend to quote gallons at overflow, not at operating depth!

I ran these calculations:

Top 3.5' of entire pool:
20 * 40 * 3.5 * 7.48 = 20,944 gal (this overstates gallons, due to rounded corners and beveled wall to floor transitions)

Hopper only, going from 3.5 water depth to 8.5' water depth - avg depth = 1/2 of difference (again, an over-estimate, but I'm not going to do a more accurate calculation yet.)
20 * 25 * 2.5 * 7.48 = 9,350

So, your likely actual water volume may be closer to 30,000 gallons, than to 36,000. Even a 10' nominal hopper (9.5 water depth) would only take you to 31,000 gallons.

Quote:

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Originally Posted by smileitsachoice

aerating water to raise ph as I am waiting on Borate test strips to be delivered. . . . . Water this morning is absolutely crystal clear (the addition of the borates WOW!)

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Aeration will only raise pH if CARBONATE alkalinity is present. You don't have much, except the bicarb you just added. I don't know that I'd worry much about adding bicarb in the future. The only real reasons to use bicarb are to (1) buffer the pool and (2) add carbonate alkalinity on pools where you need a near positive Langlier index (based on pH, carbonate alkalinity and calcium levels). On your pool, with a SWCG, your pH drift will be upwards, and a high borate level will work well for you, so you won't necessarily need the carbonate alkalinity for that. And, since you have a liner pool, you don't need a positive Langlier's or SI.

I'm surprised the borate addition made such a visible difference in clarity.

By the way, thanks for the subscription!

Ben,
You are correct I had a typo in my sig. Should be 30,000 gals. I am about to change my sig. Love the site and thanks for your help.