Well... First the site has been very helpful, but my first post on here.I'm out here in Yuma, Az. It's hitting the 100's and I just took over duty on a 197,000 gallon pool here on the Army base. It is a SWC pool. They fought all last summer to keep the chlorine in it. I found the stabilizer was non existent in it.Salt content is dead on. I got the chlorine readings up to 5.0ppm....Too high they want it at 3.0ppm. They shut down the pool today and I'm looking for quick advice. I cant figure out how much neutralizer to put in the water without killing all my work. All my tests and chems are dead on but they want it at 3.0ppm. I need it open quickly. I have tried searching charts,etc which got me here to TFP. Any suggestions, time is not on my side at this point? Thanks in advance,Mark
I'm in over my head!
- Thread starter poolmanaz
- Start date
3ppm is a perfectly acceptable chlorine level if you maintain a low level of CYA stabilizer of only 20 ppm, the problem is in order to get away with only 20 ppm of CYA in a pool exposed to a lot of sun light you would have to install massively oversized SWG's to produce enough chlorine to beat the losses to the sunlight. The underlying question is why the 3 ppm FC limit?
Ike
p.s. in my limited experience a little bit of chlorine neutralizer goes a long way, I suspect even on a pool yours size it would only take a couple of pounds or so to drop you FC by 2 ppm (well maybe 3 or 4 pounds, I do remember using it in an emergency I had with my pool and used only about 1.5 pounds to drop 6 or 7 ppm of FC, of course your dealing with a pool 5 times bigger or so)
Ike
p.s. in my limited experience a little bit of chlorine neutralizer goes a long way, I suspect even on a pool yours size it would only take a couple of pounds or so to drop you FC by 2 ppm (well maybe 3 or 4 pounds, I do remember using it in an emergency I had with my pool and used only about 1.5 pounds to drop 6 or 7 ppm of FC, of course your dealing with a pool 5 times bigger or so)
Arizona state codes for commercial/public pools (what they call "public or semi-public") require chlorine to be from 1-3 ppm (bromine from 2-4 ppm; spas from 3-5 ppm chlorine or bromine) based on the DPD test or the ORP being at least 650 mV (no upper limit!).
Since you are using a saltwater chlorine generator, then if you want to prevent algae growth without using any supplemental algicide (e.g. Polyquat 60) or phosphate remover, then with 3 ppm FC max you shouldn't have the CYA be any higher than 60 ppm. Though this means that you will have to size your chlorine generator higher than you would if you could do 4 ppm FC with 80 ppm CYA, it should still be reasonable for you.
Of course, if this is a residential pool, then what is the issue? It sounds like this must be a commercial/public pool. [EDIT] I see from your initial post that it is a very large pool so clearly in the "public or semi-public" category. [END-EDIT]
Since you are using a saltwater chlorine generator, then if you want to prevent algae growth without using any supplemental algicide (e.g. Polyquat 60) or phosphate remover, then with 3 ppm FC max you shouldn't have the CYA be any higher than 60 ppm. Though this means that you will have to size your chlorine generator higher than you would if you could do 4 ppm FC with 80 ppm CYA, it should still be reasonable for you.
Of course, if this is a residential pool, then what is the issue? It sounds like this must be a commercial/public pool. [EDIT] I see from your initial post that it is a very large pool so clearly in the "public or semi-public" category. [END-EDIT]
Thanks for the quick replies! Isaac it has 24! Pentair cells! That's been the problem here is the CYA has never been set. I got it right (I think) and these things are cranking it out. We see temps near 120 and pool water in the 90's so I don't want to drop everything out with the Neutralizer. Well heading out to check it again. I think I'm going to add 3 more pounds of Neutralizer (I put three in yesterday) and see where she goes.Thanks for the input guys, I will update later,pm
You are doing what you need to do. Just keep adding the Thiosulfate a little and test about an hour later Keep the pumps running and shut the swcg's off until you get to about 3 ppm FC.
Once you get it close to 3 ppm fire the swcg's back up and run the percentage down about 25% from where it is now. You'll have to watch it pretty closely the next few days in order to get the swcg's dialed in to keeping the FC at 3 ppm.
Once you get it close to 3 ppm fire the swcg's back up and run the percentage down about 25% from where it is now. You'll have to watch it pretty closely the next few days in order to get the swcg's dialed in to keeping the FC at 3 ppm.
Below is a chart from an old spreadsheet I have laying around. I cannot vouch for the accuracy. The instructions on an old bottle states 2 oz per 10K gallons (equals 39.4 oz in a 197K pool) reduces Chlorine 1 ppm. I am assuming the bottle is not 100% Sodium Thiosulfate, so the dosage would depend on your percentage. Hope this helps.
To Decrease Free Chlorine Using Sodium Thiosulfate ; 5-Hydrate (100%) in 197,000 Gals
Decrease
in ppm Ounces
1 ppm 27.58
2 ppm 53.19
3 ppm 80.77
4 ppm 106.38
5 ppm 133.96
10 ppm 267.92
15 ppm 401.88
20 ppm 535.84
30 ppm 803.76
50 ppm 1339.60
To Decrease Free Chlorine Using Sodium Thiosulfate ; 5-Hydrate (100%) in 197,000 Gals
Decrease
in ppm Ounces
1 ppm 27.58
2 ppm 53.19
3 ppm 80.77
4 ppm 106.38
5 ppm 133.96
10 ppm 267.92
15 ppm 401.88
20 ppm 535.84
30 ppm 803.76
50 ppm 1339.60
I went out and discovered the cells were stuck in the "boost mode' I can't seem to get them out of Boost mode. It does not have a main control box as stated in the Pentair manual. I'm waiting for a reply from Pentair.Thanks Guys!
No wonder it's pounding the FC out!! (Pun intended) 
Post back what Pentair tells you.
Post back what Pentair tells you.