Salt Water Generator / Intex Pool Question/advice

[Indywar]

I have been using Intex's saltwater chlorine generating (SWCG) system for several years and have been complete satisfied. I would dissolve the proper amount of NaCl, turn on the pump/generator, dial in the time to 4 hrs and the pool was perfect for the rest of the year.

This year, the generator/pump electronics malfunctioned, and I had to purchase a new one. It looked different than the old system (clear electrolytic cell and copper generator), but what could go wrong? A lot! I have been unable to get my pool stabilized since Memorial Day.

I had the beginnings of algae (based upon water color) due to a lack of chlorine generation a week ago. Since then, I have shocked the pool (16'x48" round, ~ 5000 gal.) twice, added stabilizer twice, and added muratic acid. The pH was high but now is in the 7.2-7.4 range. I measure the chloride using the drops (HTH 3 way kit), and measure the pH with a pH probe. I have measured the chlorine 1 hour after starting the SWCG (in the evening), the next morning, and before starting the SWCG the following evening (I have been running the SWCG for 6 hrs at night, even though the manual recommends 2 hrs for my size pool). After ~ 1 hr, chlorine in the pool measures ~ 1ppm, in the morning about the same, and by evening no color is detectable.

The current condition of the pool is cloudy.

Any advice? I have already returned 1 of these units, and the new replacement showed up yesterday.

Thanks,
Rob

[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]

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