SWG Conversion Going too Smoothly...What am I missing?

[J_L_D]

Had a rip in my liner and decided when I replaced it, I would start back with SWG system. Had been using bleach for last 3 seasons, but last one didn't go as well as first two, which went great. Anyway, bought a CompuPool CPSC48, a 240v timer, cut-out the tab chlorinator, installed the new equipment, and waited for liner. The guys cut in the returns, lights, pressure pump connection, and skimmers...yesterday.

We turned the pumps on and started circulating. He mixed 3 "scoops" of chlorine in a 5 gal bucket and put it in, along with 2 gallons of acid. I checked some chemistry and this is what I had:

FC: 10
PH: 7.2
CC: ? (My TFT100 no. 3 reagent bottle broke...all but a couple drops leaked out...but they didn't change the color)
TA: 100
CH: 0

I couldn't test salt, as I haven't ordered a kit yet, but I pushed the power on button on the CPSC48, scrolled to the Salt screen, and after a minute of calibration it said OK...went back to home screen and it started making chlorine at 70% by default.

I took (2) 3 lb. bottles of CYA and put each into a knee-high stocking and dropped (1) each in the skimmer baskets. Turned off the SWG as per instructions when adding chemicals. That's it.

Today I'm going to try to have the salt tested, because I think I must be on the low side (3000 ppm), but I'm glad I didn't add any more than I did yet, which was 560 lbs.

Once the CYA is dissolved I should have maybe 30 for a CYA reading, and will probably take it up slowly from there, as needed. I'd rather keep FC in the 2-3 range and think the SWG should be able to do that?

Everything seemed to sort of fall into place with no hiccups so I wanted to ask what's next, or what to look for. Water is clear but I hope to get it even more clear after a few days running the sand filter 24/7.

Thanks for your input.

 

[Melt In The Sun]

Sounds like you're not missing anything, it typically is that easy. If your system is happy with the salt level there's no need to match any specific number. Increasing CYA gradually is a good idea...you don't say how high you want to go, but I'd say 70 or 80. Your system will work harder to keep it at FC 2-3 @30 CYA than 5-6 @75 CYA. Seems a little counter-intuitive, but it's true!

Do you really have 0 CH? Not that it's a problem if you do...

 

[jblizzle]

What type of chlorine was added? If it was dichlor, that will have added some (although not much) CYA already.

I think you have a good plan to add enough to get to around 30ppm and then to test it, but like MITS said, I would then immediately raise it up around 70+ppm to better protect it from the sun and let the SWG work less.

Keep an eye on the pH as the SWG tends to make it rise. Also your TA is a little high so that will aid the pH in rising as well. As you keep lowering the pH, the TA should come down and thus slow down the rising pH.

 

[linen]

Hey J_L_D, maybe update your sig with the swg info now so you don't forget to do it.

:!: What is your current ph?

2 gallons of acid. I checked some chemistry and this is what I had:

That is a huge amount of acid (if it was 31% MA). Check your ph right away :!:

Once the CYA is dissolved I should have maybe 30 for a CYA reading

Assuming you had no cya in start with, 3 lbs of granular stabilizer will only raise your 24000 gallon pool to 15 ppm.

Have you read?: http://www.troublefreepool.com/pool-school/water_balance_saltwater_generator

 

[J_L_D]

I was wondering about the CH. The test I think I used 20 drops then added 5 of another, and it turns red if Calcium is present...or something like that. I looked back at my old water test and I had written down 30, but new water indicates no calcium. I wonder if I need to add something? I wonder if my almost 3 year old reagents are accurate.

I went back and posted the PH I read yesterday which was at 7.2. I was thinking the CYA my bring it down even more, but then the SWG and aeration would bring it up. Not sure where the TA will settle out.

I know the 60 or 70 range is recommended for the CYA, and yes it seems counterintuitive, and not per the mfr. recs, which is why I wanted to experiment with it before taking it up that high (knowing that reversing that is a bit of a task and would also cost $$ for water and salt). You got me thinking...I wonder how one could tell in which scenario you list above, that the cell is working 'harder'. My other thought was that the lower levels would be easier on the liner, and swimmers. My old one faded badly, but I don't know how it spent it's first 5 years in the pool.


linen...I went back and added to original post. I read 7.2 last night. Will check it again soon... And it was 6 lbs. of CYA... 3 in each skimmer

 

[linen]

linen...I went back and added to original post. I read 7.2 last night. Will check it again soon...

Okay...with an addition of 2 gallons of MA, I would have expected your ph to be much lower than 7.2. One thing to remember, when your FC is above 10 ppm, the ph test is not valid (and typically reads high). Low ph can really damage vinyl liners (much more than high FC)...and we wouldn't want your brand spanking new liner's life shortened

 

[J_L_D]

I knew it was going to smoothly ...but hopefully it's still ok. I see what you mean about the acid, and when I play with the pool calculator, it only needed 59 ounces for a reading of 7.2 (I read the PH at around 8.2 that morning, before he added the Chlorine, so hopefully that part was accurate...but that's the top of the scale so who knows). I will look again at the PH but I think it bottoms at 7.2 so it's kind of hard. You're right about the 2 gallons...Pool calc says that would take it from 8.2 to 6.4, if it's 24,000 gallon (which I'm not sure of...builder sort of mentioned it). How can I test PH below the Taylor scale? I have a TFT-100.

One other thing I don't know how it figures in, he mentioned that the fill water was probably around 200 TA, although we didn't test it. I guess he's just used to what's out there. I wonder if that's why he added so much acid? I can go get some bicarb or whatever if I need to.

SWG added to sig

 

[jblizzle]

You can tell it is "working harder" by what % setting you are having to use to maintain the required FC level.

You may find that the % is lower to maintain 5ppm at a higher CYA than to maintain 2ppm at the lower CYA.

 

[RobbieH]

What bizzle said. I maintain 5% at 80 ppm CYA. I realize the min is 4%, but there is no point in risking falling under when it's not that much harder to stay at 5.

 

[J_L_D]

I had pulled a sample yesterday morning and I took it to the pool store after work yesterday.
Here are the results (NOTE: It wasn't enough water for proper salt test, but she used the strips and said it would be close)

TA: 128 (I had 100 - do the reagents lose accuracy over time or is that normal variation)
PH: 7.4 (I had measured 7.2 the day before, but my color scale test confirmed the 7.4 last night)
CYA: 8 (Some of it is dissolving, but going very slow in a sock in the skimmer...pulled one and dumped in skimmer, will dump other one in deep end)
FC: 4.0 (My color scale seemed close to 5 when I got home)
CH: 21 ( I read 0)
Iron: 0
Copper: 0
Salt: 3350

So it looks like everything was good after all. I don't know how 2 gallons of acid didn't take it down to near 6.4 as per pool calculator. Actually it would have been even lower than that on the calculator as I did it for 24K gallons. I think my pool size must be less than that, IF the 3350 salt is correct. Using the calculator, if I started with 90 ppm salt, and added 560 lbs to a 21K pool, that would give me the 3350 ppm the pool store saw. So 2 gallons of acid would have taken it even lower than 6.4. But if the TA was really 200 to start with, as the builder suggested, maybe that would explain it...I don't know.

On the CYA issue...if I can ever get it dissolved and confirm that I have at least 30 ppm...I could get the system set up for maybe 8 or 10 hours per day at x% SWG (maybe 50% don't know yet). And if that's holding say 3 ppm CL for a couple weeks, and then I add enough CYA to take it up by 10 ppm, theoretically, the CL ppm produced would come up, because it would be working better/more efficiently. That's correct, right? I mean if I have to keep turning up the % on the SWG as I increase the CYA, then it's not working more efficiently. If CL goes up with the addition of CYA, then monitor for a week or two and repeat to see if it goes up again...Then stop when it doesn't go up faster than the required FC ppm. I mean wouldn't it (FC) need to go up more (faster) than the rate the "required FC for x-amount of CYA" is going up to be working more efficiently? I'm new to SWG so may not have that right or be expressing it well.

Do you think the TA will come down over time, as I run the SWG and add acid?

Thanks for all the input. I found this board when I first bought the green swamp in 2010 and have found it very informative for various issues since then, including turning the green swamp blue.

ps. Is the SALT ppm test I describe above a good way to verify pool size? I read somewhere the tap water may have 100 or 200 ppm, but it wasn't tested. The pool store said she didn't even find that to be the case...(less than that). So I just tried to back into how many gallons 560 lbs would take up to 3350 ppm.
The label on the liner box said 37-9" x 19'-6" or something like that. But it has lots of curves and reverse reverse radius sides...I don't know how I'd ever measure it.

 

[JasonLion]

Never add CYA directly to the pool. Do not pour it into the deep end. CYA can damage the pool surface.

If you add acid regularly, the TA will come down. It may take a long time however.

Trust your own test results and ignore the pool store results. The odds are that your results are far more accurate.

There is lots of error in all of the common salt tests, typically +-400 or worse. Your approach to guessing the pool size with salt addition is sound, but the precision of the result is low. You can use a whole sequence of different chemical additions over time to try and improve the precision of your guess of the pool volume.

As you add CYA you will be able to turn down the percentage setting on the SWG.

You should raise CYA to between 70 and 80. Don't use the procedure you described for guessing an appropriate CYA level. Your process would favor an infinite CYA level, which has other completely unrelated major problems. Just be cautious not to overshoot and raise CYA too high. It is fairly easy to raise CYA, difficult to lower it.

 

[J_L_D]

Yeah, I was wondering about the pool surface as you mention. The MSDS I read on CYA indicates about 3.5-4 ph, and it doesn't seem like a good idea for that to rest on the vinyl, although those are the instructions on the bottle (pour in deep end). I will dump the other sock into the skimmer rather than the pool.

I think I'll order a Taylor drop test salt kit...then my salt level, and pool size, will be more accurately known. I will put the DIY fountain in to aerate and try to lower the TA and add acid as needed. The CYA may bring it down a little as well. Then maybe I can measure the acid I add in the future and watch the change in ph to help confirm the pool size.

I wasn't going to go over 70 on the CYA, even using the method I described to test. I could still use it up to that point, and confirm that I'll be turning SWG percentage down as it goes up. I assume someone has already done this or something similar or it wouldn't be advised. That would be great and save on the salt cell. Right now I just need to get the CYA dissolved, turn on the SWG and start getting things dialed in. According to pool calculator I still only need 3 ppm FC with 70 CYA so that does not seem too high, although that puts shock level (if needed) at 20, which is a lot of chlorine.

The manual suggests 100-120 TA and depending on which test result I use, I'm pretty much there, but will try to get it down to 80.
One other thing...my calcium reading 0, per store 21. The manual says 200-300 and Calculator says 50-300. The pool store said get it up to 100 to help prevent having problems like brittle vinyl liner 4-5 years down the road. Should I add more chemicals for that? I would prefer to add as few as possible, get everything balanced and let the SWG do it's thing, adding a little acid now and then, push a couple buttons.

Thanks for your help.

 

[jblizzle]

Aerating does not lower TA, it only raises the pH. When you add acid, it lowers the pH and the TA.

 

[J_L_D]

Right, I didn't really state that correctly. Aerating raises the PH, effecting a need to add acid and thereby lowering TA. Hopefully the 100-120 TA is not too far off as to cause problems but I'll try to get it down some. My understanding is that the SWG will cause the PH to creep up, requiring the addition of acid (lowering TA). I have read that the SWG Chlorine is PH neutral, yet the PH will still rise eventually with use, so maybe over time the TA will keep going down as I add acid to correct the PH.

 

[linen]

so maybe over time the TA will keep going down as I add acid to correct the PH.

You can take that approach, but you will be adding acid frequently at first. Getting your TA down to 80 (or maybe even lower depending on your pool) will reduce how often you have to add acid. In fact in my swg pool, I adjust at the beginning of the season (TA and ph) and that is it for the swim season, my ph stays stable.

 

[J_L_D]

So you don't have to add acid or other chemicals all season...that sounds fantastic. What adjustments do you do at the beginning of the season to achieve proper TA and PH... I would like to try to get it down... I have a PVC Spray Fountain I made that I can hook up and divert all the water from one of the (3) returns into the air, via about (20) holes drilled into about a 2 ft. long piece of 1.5" PVC. Should I hook that up or just keep dumping acid in? Or Both...

 

[linen]

So you don't have to add acid or other chemicals all season...that sounds fantastic.

First, recognize that each pool is different. Yes, in my case I did not need to lower ph after my initial balancing done at the beginning of last summer. Keep in mind, my swim season is relatively short (mn). In addition I have Borates in my water that also buffers the ph.

What adjustments do you do at the beginning of the season to achieve proper TA and PH... I would like to try to get it down

In addition to having borates in my pool, I got my TA down to about 55 ppm. I would suggest that you do not go that low on your pool for now. I would shoot for 80 ppm and see how stable your ph is for awhile after the adjustment.

Should I hook that up or just keep dumping acid in? Or Both...

Kind of both. Have you read?: http://www.troublefreepool.com/pool-school/lowering total alkalinity Basically you raise ph up with aeration, then lower it back down with the appropriate amount of acid (which also lowers your TA). Then repeat, repeat, repeat...until your TA is down to where you want to stop.

 

[J_L_D]

Thanks. Yes, that confirms what I thought. I read all the Pool School a few years ago when I got started, but some stuff probably seeped out . I sort of figured I would be adding some acid throughout the year, but maybe less than when I was using Bleach. Our season is long here, and I never "close" the pool, just stay out. My last swim was mid-October, and probably will be back in it in a few weeks. I'm looking forward to the new liner, fresh water, and SWG system. Been sucking air into my strainer basket when I close the 3-way to either the main drain or skimmers, so just ordered new o-rings for pump drain plugs, pump suction union, 3-way valve cover and stem. Hope that helps.