Salt Water Generator / Intex Pool Question/advice

[aylad]

Hi Rob,

You say that you've added stabilizer twice--what is your current CYA reading? (With the disappearing dot test, not strips). The two things that immediately come to mind are that 1)you don't have enough stabilizer in the pool, so you're losing all your chlorine to the sun, and 2) you still have some sort of chlorine demand going on in the pool that's using it up--we've seen a whole lot of that this year. What was your CYA level when you closed last year, and what was it at the beginning of this year?

You can rule out chlorine demand by testing your chlorine level at night, and again in the morning before the sun hits the pool, and comparing the two--if you've lost more than 1 ppm of chlorine, then you have something in the water that's using it up, and you need to shock the pool and maintain that shock level until you can pass that test. If there's 1 ppm or less chlorine loss, then it's possibly stabilizer.

Have you tried testing the water right after it comes from the cell (return stream) to see what the Cl level is as it comes back into the pool?

[PoolDoc]

Hi Rob;

I think you've been lucky, before, and now you're not. So, it's time to actually have a plan.

For starters, you can't measure chloride (salt) with a 3-way; you can measure chlorine (not chloride), pH and alkalinity. AND, using a pH probe could be a BIG part of your problem -- because I'm guessing you do not have the pH probe calibration solutions. That means, that your probe could now be reading ANYTHING, except the correct value.

Read through the Intex recipe sticky in this section; learn to do your pool withOUT the SWCG, and then turn the SWCG on, and see if it works.

But . . . first you have to get a test kit. Go get a cheap OTO/phenol red test kit, and find our what your pH and chlorine levels are. Turn your SWCG OFF.

Meanwhile, for a 5,000 gallon pool, add 1 gallon of PLAIN 6% bleach each evening. Test with OTO before each addition; if the result is dark yellow, or orange, skip that addition.

[Indywar]

Thanks for the reply PoolDoc.

Sometimes it is better to be lucky than good I suspect there has been a fundamental engineering change to the SWCG (in addition to adding a copper generator that is useless) that has caused the change.
But anyways, the sodium chloride (salt) is measured by a dipstick and/or a conductivity meter, not by any chemical means. The pH probes is indeed calibrated with Fisher scientific pH 4 and pH 7 standards (I am a chemist and microbiologist during the day, and easily have access to the expensive pH meters to have an orthogonal technique to compare my pH probe to. In addition, I have used the phenol red (significantly less sensitive than our pH meters), yet another orthogonal technique, to confirm the pH probe readings).
I think I mentioned previously that I did have a test kit (OTO style), but if not my omission. I purchased a 6 way kit tonight, and have posted the results in a previous thread (approval pending).

I appreciate the advice to try to get things under control without the SWCG, trying to isolate if that is truly the problem. That is a good plan. I will also follow the advice with the sodium hypochlorite and report back.

Thanks again for the advice,
Rob

[PoolDoc]

But anyways, the sodium chloride (salt) is measured by a dipstick and/or a conductivity meter, not by any chemical means. The pH probes is indeed calibrated with Fisher scientific pH 4 and pH 7 standards (I am a chemist and microbiologist during the day, and easily have access to the expensive pH meters to have an orthogonal technique to compare my pH probe to. In addition, I have used the phenol red (significantly less sensitive than our pH meters), yet another orthogonal technique, to confirm the pH probe readings).

Not the response we usually encounter! But, you did lead me astray with this:

I measure the chloride using the drops (HTH 3 way kit)

(Shame on you!)

Shocking is not the hazard it's made out to be. People are very chlorine resistant -- though swimwear is not!

Anyhow, we'd gradually been moving toward a full blown rejection of all the NSPI / APSP / CDC / EPA "Keep people out of the pool till the FC is less than 3 / 5 / 10 ppm", though we hadn't quite gotten there. Now, we have.

I've known for some time that those regulatory limits were pulled out of the air. But until recently we didn't have positive confirmation of the safety of high levels of FC exposure. But, we had the issue raised this spring, and in the investigation that followed, I found that an old dermatological treatment, a "bleach bath" (> 50 ppm FC), is STILL actively and regularly prescribed for a variety of skin problems. Here's the link to a Google search on the topic.

So, when you shock, let it circulate long enough so their suit (or eyes) won't hit a hot spot . . . and you're fine!

[aylad]

But make sure that whatever's using the chlorine is dead--it's not the level of the chlorine that is a concern, so much as the fact that if the chlorine is fighting something in the water, then there's not any left over to fight additional people-goo, and if somebody in the pool has any sort of virus, the chlorine won't be available to act on it....

[Indywar]

PoolDoc, my bad. Amazing the difference in a couple of letters: chloride, chlorine, nitrate, nitrite, etc. You are right to scold me for not being accurate

It is amazing the paranoia the government, and in particular the yahoos in the EPA cause. As a scientist I am skeptical of anything coming from the EPA, the Center for Science in the public, and similar NGO that don't have any relevant data to back up their claims. Often they will cite some obscure study in the hinderlands of France with a maximum of 100 subjects, and then claim the 300 + billion people on the earth will be similarly affected. (Sorry for the soapbox).

Thanks for the advice. Will get to the shocking. Also, should I continue to increase the CYA. The pool place has a broad range of 30-150 ppm. Is higher better in this case?

Aylad,
Good point, although I am less concerned with the viruses as opposed to water borne bacteria. The cells of virus are more susceptible to disinfectants, even low levels and are incapable of reproducing without a host. Bacteria commonly grow in water environments (e.g biofilms that are at water fountains, in water coolers, etc.). Nonetheless, still good points.

Thanks again for all the advice. I have some work to do to get this stabilized.

Rob

[PoolDoc]

Good point, although I am less concerned with the viruses as opposed to water borne bacteria. The cells of virus are more susceptible to disinfectants, even low levels and are incapable of reproducing without a host. Bacteria commonly grow in water environments (e.g biofilms that are at water fountains, in water coolers, etc.).

As far as we know, the high risk events in pools are all related to person-to-person transmission, usually fecal-pool-oral or snot/spit-pool-oral. And, the culprits are usually either viruses OR amoebic oocysts. The data I've seen suggests that pathogenic viruses are MORE, not less, resistant to chlorine. Also, though these cases are not biofilm related, they ARE fomite related, and killing fomite associated pathogens is a LOT harder than killing planktonic pathogens!

There some common low risk events, associated with P. aeruginois and biofilms (hot tub itch; otitis externa) but those don't kill anyone or even make them very sick.

One rare exception: Naegleri fowleri is VERY dangerous and can actually live in pools, apparently.

Right now, the pool is the problem -- but this fall, if you are interested, it would be very helpful to have a working microbiologist looking over my shoulder as I'm putting SwimmingPoolResearch.com together. I've got about 8 Gigabytes of peer-reviewed articles to index!

Oh, and you're preaching to the choir, at least with me, about trusting "scientists" and especially government "scientists". Here something my older son (a recent biochem grad) found for me:

"It has long been known"... I didn't look up the original reference.
"A definite trend is evident"... These data are practically meaningless.
"While it has not been possible to provide definite answers to the questions"... An unsuccessful experiment, but I still hope to get it published.
"Three of the samples were chosen for detailed study"... The other results didn't make any sense.
"Typical results are shown"... This is the prettiest graph.
"These results will be in a subsequent report"... I might get around to this sometime, if pushed/funded.
"In my experience"... once.
"In case after case"... twice.
"In a series of cases"... thrice.
"It is believed that"... I think.
"It is generally believed that"... A couple of others think so, too.
"Correct within an order of magnitude"... Wrong.
"According to statistical analysis"... Rumor has it.
"A statistically oriented projection of the significance of these findings"... A wild guess.
"A careful analysis of obtainable data"... Three pages of notes were obliterated when I knocked over a glass of pop.
"It is clear that much additional work will be required before a complete understanding of this phenomenon occurs"... I don't understand it.
"After additional study by my colleagues"... They don't understand it either.
"Thanks are due to Joe Blotz for assistance with the experiment and to Cindy Adams for valuable discussions"... Mr. Blotz did the work and Ms. Adams explained to me what it meant.
"A highly significant area for exploratory study"... A totally useless topic selected by my committee.
"It is hoped that this study will stimulate further investigation in this field"... I quit.

[Indywar]

Hi Aylad,

My CYA reading (dot test) was ~ 48ppm, pH=7.2, chlorine after 3 hrs of running SWCG (10:00 PM) was between 1-2 ppm, total alkalinity~200ppm.

Honestly, I never measured CYA, or anything other than pH with the other chlorinator the last several years. It was that dependable. Once I got the pH in range, & added the correct amount of NaCL at the beginning of the season I didn't add anything else all year: no stabilizer, maybe minor pH adjustments one or twice per season=crystal clear water with appropriate chlorine conc..
After pool season I drain the pool and store it.

As far as CYA earlier this year (based on the local pool shop....after reading your article on this forum I'm not sure what they are worth) 6/8/2012 CYA=10 ppm, 6/18/2012 = 25 ppm.

I tested the water right in front of the jet, where the chlorine conc. should be the highest and it was ~ 2 ppm.

I can check in the AM to determine chlorine loss, however there is an extra variable: the SWCG runs in the evening, so the chlorine should increase from now to the morning. If something was scavenging the Cl2, then the extra Cl2 produced by the SWCG could mask that effect. Anyways, I'll try to measure it tomorrow AM.

Thanks for the feedback. Unless you have other advice I will probable shock the pool tomorrow. How long should the kids wait after shocking before swimming?

Thanks,
Rob

[aylad]

There's really no reason to check for chlorine loss if your SWCG is running through the night--the whole point is to determine if something is consuming your chlorine, or if it's not being generated--and if it's running overnight, then any difference in the two readings is pretty much meaningless. If you need to shock the pool, you need to shock it and hold it there until you're not losing chlorine overnight. Could be one night, could be more, it just depends.

The kids should wait until you're finished shocking (no longer losing chlorine to anything other than sunlight) and until the chlorine levels have come down to an adequate level in your pool, which for a CYA of 48 should be at least 3 ppm before swimming. If you have something in the water that is creating a chlorine demand, then there's no chlorine left over to kill the viruses and bacteria that we're trying to protect the swimmers from!

[Indywar]

Checked Chlorine & pH at 7:30 AM: chlorine=1 ppm, pH 7.2