Cyanuric acid missing

[PoolDoc]

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)

[smileitsachoice]

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!)

[kelemvor]

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.

[smileitsachoice]

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.

[PoolDoc]

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.

[PoolDoc]

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!)

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!

[smileitsachoice]

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.