SWG questions re: settings and chemistry

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W

Wolfman

0
Aug 5, 2009
10
Greetings all....new to this forum but not to pool problems...

All has gone reasonably well for the last 6 years of pool ownership...but in the last two weeks I've been stumped. My AquaRite SWG does not seem to be working properly OR I have a yet undiscovered problem with my water chemistry (according to the rude customer service reps at Goldline). Here are the stats: 30K gallon IG plaster pool (6 yrs old), DE filter and Aquarite SWG with 2 yr old T-15 cell. Pump operates 10 hrs per day at 65% setting....and has for 2 years with no problems...till now. No changes in types and amounts of chemicals routinely used.

FC 1 (by addition of bleach last night, otherwise "0")
TC 1
PH 7.6
TA 100
CYA 80
Salt 3800 (SWG reads 3400)
Phosphates .1 ppm

Had the cell tested due to no production of chlorine...cell tested bad at one shop...tested good at second. According to readings at electronic unit (and Goldline), chlorine production is taking place. After reinstallation, a FC reading at return (undiluted by existing pool water) is 2 ppm...with pool water at .5 ppm.

QUESTIONS:

Have I missed something in the pool chemistry that is causing my recent lack of FC?

Is my SWG generating an "appropriate" amount of chlorine?

Having read through this forum and Pool School, should I be targeting my FC at 4 ppm instead of 1 to 2 ppm?

Sorry to go on in such depth, just tried to give enough info to let the experts have enough ammo to answer. Thanks in advance for your assistance...have learned ALOT so far!
 
Welcome to TFP!

In order for the pool to be completely trouble free, you should target a higher FC level, around 4 or a little higher. When you run the FC level below that you can often go a long time before you will get algae, but eventually you will get algae.

The test you did shows that the cell is generating chlorine. It might not be generating chlorine quite as quickly as it did when it was new, but raising FC by 1.5 means that it is working correctly. Have you done a visual inspection of the cell? The cell pates should be either black or silver and free of any crusty white buildup. Calcium buildup will reduce the efficiency of chlorine production.

Assuming the water is clear, I would shock the pool to make sure you are completely algae free and then turn up the percentage a little and aim for a FC level of 4 to 5 and see what happens.
 
I suspect a nascent algae bloom. Shock to about 20-25 ppm with bleach or liquid chlorine and that should solve the problem. After that keep the FC at about 4 ppm. You might also want to consider adding borates to your water.
How quickly does your pH rise and how often do you have to add acid.? Does your pH ever go about 7.8?
 
Thank you all for such prompt responses!

I did have a small yellow algae problem a few months ago...shocked, vacuumed, shocked and cleaned the filter. I suspect that, after viewing the info on this site, I did not shock to high enough levels.

I will shock tonight and see how it goes from there.

I use a Taylor DPD test kit, confirmed/contradicted by 2 different pool stores, and an occasional free test from the neighbor's pool service!

I'm adding acid on a weekly basis...readings do go up to 7.8, then reduce to 7.5 to 7.6 with muriatic acid.

Thanks again...I'll let you know the results!
 
If you used a specialty algaecide with Sodium Bromide at the primary active ingredient, usually with Mustard or Yellow in the name, the sodium bromide is reacting with your chlorine process.

Shocking with chlorine and keeping it around 10 ppm for the next week or two should get you back in operation. But add the chlorine, leave it for several days and add more as needed. Turn your salt system off until after this period and see if the chlorine will hold for 3-4 days without needing additional chlorine. After that, you can turn your salt system back on. It shouldn't need more than two weeks.
 
Ideally you should supplement your test kit with an FAS-DPD test - it cannot be topped when it comes to precision and reads FC and CC up to 50ppm. You can buy the individual test for around $25. Both Taylor and TFtestkits.net sell the individual test.

I agree, shock the pool (refer to the CYA chart for your shock level) and turn off the SWG. Then with an FAS-DPD test, perform an [urlhttp://www.troublefreepool.com/pool-school/overnight_fc_test]Overnight FC Loss Test[/url], to confirm that there are no organics which are consuming the chlorine the SWG is adding.

When the FC holds overnight, your cell should be able to keep up with additional run time, especially if you maintain it at 4, which is the lowest FC level you should be targeting.

Your TA is high for an SWG - next time you add acid, lower the PH down to 7.2 instead. A few more cycles of that and the TA should drop into the recommended 70-90 range.
 
Thanks again to all for your help!

Sean - I didn't use a specialty algaecide, just several bags of "pool shock" to superchlorinate....but clearly (by the CYA chart) not to a high enough level. I shocked last night with liquid chlorine to 25 ppm....we'll see how that goes.

Waterbear - I will be going to get the CH tested by this weekend, and I'll post that as well as the current numbers. I've started reading the articles on borates, and they make sense. Up until this FC fiasco, my biggest routine was to keep the PH within range. Borates sound like the answer......I'll look into that right after this FC episode is resolved.

Thanks to all...again!

George
 
Morning!

Maybe I'm getting ahead of myself here....but it's been hammered into me (and a lot of others I know) that chlorine levels nearing 5 ppm are unsafe to swim in.....and that they should be kept in the 1-3 range...the lower the better.

If I run my SWG at 4 (with a target of 6, according to the CYA chart), am I pushing the limit? I originally got the SWG because of it's lack of chlorine-like side effects (bleaching, green hair, etc.)...am I going to lose some of those benefits with an increased chlorine level?

My main concern is the grandkids...a couple of them are very young and LOVE to spend hours in the pool. If there's no short answer, please direct me to any articles or threads that cover this...I'm retired so I have a lot of research time....you all probably still have full time jobs (ha! ha!)

Thanks again...

George
 

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How high the FC level can be and still be safe depends on what the CYA level is. Anything up to shock level for your CYA level on the Chlorine/CYA Chart is safe to swim in.

The "traditional" rule limiting chlorine to 5 ppm is based on having CYA at zero. As soon as the CYA level goes above zero the maximum allowable FC level goes up rapidly. CYA basically buffers the chlorine, keeping most of it out of it's active state, so the actual active chlorine level is far lower than the measured FC level. The more CYA there is, the more chlorine is held in it's inactive state.
 
George - Green hair is from copper in the pool, not chlorine. If someone gets green hair, then the copper levels of the pool (s) they are swimming in are elevated, possibly from "mineral Ionizer systems" or copper-based algaecides. Also some companies are putting copper in their trichlor pucks.

Nexxus makes a shampoo called "Aloe Rid" that removes the green. :wink: I've tried all the "swimmers" shampoo and that's the only one that got the green out successfully. :goodjob:
 
Here's an update-

First, "Mom"...thanks for the copper refresher and the shampoo update....I know several neighbors who will be REALLY happy with that info!

Got my FC up to 26 last night, tested around 24 this morning. Pool looks amazingly clear.
Loss indicates something is still eating my FC.

Checked the FC about an hour ago.....9.6 !!!! 15ppm loss over the day! (no...no pool leak!)
Added 4 gallons and hope to bump it back to around 25....will test later and again in the morning.

Now I see why I need a FAS DPD test....it's a pain diluting the samples....but the FC loss is so great that my OTO and DPD will work till I buy one tomorrow.

Should I bump the FC in the morning to shock levels or just wait till the evening?

Thanks again for all your advice....it's been solid so far.

George
 
Diluting the sample increases the uncertainty of the test. Usually for the DPD and OTO drop tests the comparator only goes up to 5. If you're diluting 4:1 or 5:1 to get that 26 reading, I'd say 24-26 is within the range of uncertainty of the test (with the diluted sample).

The description of the overnight FC loss test assumes you're using FAS-DPD with a 10ml sample. FAS-DPD uncertainty is +/- 1 drop, which with a 10ml sample is +/- .5ppm, i.e. a 1ppm difference can be just the uncertainty of the test. Color-matching the OTO or DPD tests is not that sensitive.
--paulr
 
I would go ahead and bump it this morning and then again tonight.

Keep in mind you will lose roughly 50% of your chlorine to sunlight anyway, regardless of how high it is. That is why the overnight loss test is so important, it takes the sun out of the equasion and pinpoints organics.

Good luck! :wink:
 
Morning all!

Well, my FC held through the night.....bumped it up to 32 last night. I'll keep the level up throughout the day and do the Overnight Loss test again tonight to be sure (using FAS DPD). Hate to be overly optimistic, but it looks like there might be light at the end of the tunnel.

Now if my salt cell can maintain a 4-6 FC level, I'll be a happy camper......


Thanks AGAIN to all for walking me through this.....

George
 
Greetings all!

The good news is my chlorine is holding on the Overnight Loss test.

I'm scratching my head over some of my test results though.

Had my CYA tested twice at 100 in the last 2 weeks, once as recently as last Friday. No loss of water4 due to leaks or splashout...and I don't backwash my filter (never works well) so I always disassemble to clean. My current CYA reading is "30-50" as of today. Tested for ammonia...nothing. So either one or more of the tests were wrong....or ? I had been using bags of shock due to my cell "malfunction" for the past couple weeks which I thought would account for the rise from 80 to 100.

Anyway,

FC 10
TC 10
PH 7.6
TA 160 (up from 100 3 days ago)
CH 500
Phos. 500
CYA 30-50
Salt 3900
Temp 82 degrees

Best guess.....bump CYA towards 80, acid/aeration to bring down TA, wait for chlorine to drop to about 6 and activate the SWG.....and pray.

Any other suggestions, or am I heading towards the goal line? Thanks to all....

George
 

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