Mild chlorine bounce+strong chlorine odor but no CC in test

[Henry_R]

I thought a strong chlorine odor was usually the result of used chlorine forming CC in the water, but the FAS-DPD test shows none. So what stinks if it's not CC?

After 12am on Sunday I added 1 full gallon and 8 cups of 10% chlorine to the pool. Yesterday morning TC/FC=9,CC=0,pH=7.8,TA=170 I added 2-8oz cups of muriatic to reduce the pH to 7.6 from 7.8 hoping it takes TA down some more. It seems to be working as TA has gradually gone down from 170 peak. I've been trying to keep pH from bouncing over the last week.

That FC was higher than my goal of 8, but I thought it'd be acceptable. There were about 8 people in the pool yesterday afternoon around 5pm which is about normal bather load. I could smell some chlorine then, but no one complained.

This morning OTO test shows TC=2. FAS-DPD test TC/FC=2.5, CC=0.pH=7.5, TA=130, but there is still a strong chlorine odor. How can CC be zero with the odor as strong as it is and what stinks?

Our CYA should be somewhere between 50 (on my test) and 80 (on the pool store tests). I don't think it's 80 since the amount of chlorine loss does support that with minimal bather load.

Though our UV must be off the scale with this 100+ degree heat wave and the pool is in full sun util about 4pm when a large tree begins to shade it as the sun sets.

Am I doing something wrong with the FAS-DPD test? It says add a "heaping scoop" of the powder. I'm adding what I consider a heaping scoop, but perhaps what I consider a heaping scoop is not what the writer considers to be? To me it wuold be a little above the scoop line but not more than that.

[chem geek]

You just need to add enough powder in the FAS-DPD test to ensure there is color in the test. Usually that is one heaping scoop, though at very high chlorine levels if there is a flash of pink that then turns clear then you would add another scoop to get a color. The amount of powder is not critical for the test. I assume you are using the 10 ml sample size where each drop is 0.5 ppm. If you are using the 25 ml sample size where each drop is 0.2 ppm then sometimes I use 2 level scoops in that case.

I'm not sure about your strong chlorine odor. Is it a "bad" chloramine like smell or more of a bleach-like smell? I wouldn't have the chlorine get as low as you are getting it given your 50 ppm CYA. Try and keep it at least at 4 ppm so be in the 4-8 ppm range with your CYA at 50 ppm. That's equivalent in active chlorine (hypochlorous acid) level to around 0.08 to 0.15 ppm FC with no CYA.

[Henry_R]

You just need to add enough powder in the FAS-DPD test to ensure there is color in the test. Usually that is one heaping scoop, though at very high chlorine levels if there is a flash of pink that then turns clear then you would add another scoop to get a color. The amount of powder is not critical for the test. I assume you are using the 10 ml sample size where each drop is 0.5 ppm. If you are using the 25 ml sample size where each drop is 0.2 ppm then sometimes I use 2 level scoops in that case.

I'm not sure about your strong chlorine odor. Is it a "bad" chloramine like smell or more of a bleach-like smell? I wouldn't have the chlorine get as low as you are getting it given your 50 ppm CYA. Try and keep it at least at 4 ppm so be in the 4-8 ppm range with your CYA at 50 ppm. That's equivalent in active chlorine (hypochlorous acid) level to around 0.08 to 0.15 ppm FC with no CYA.

OK. Then I'm doing the FAS-DPD test right. It turns pink with the amount I'm adding no issues there. Yes, I'm using 10ml kit instructions state. I didn't realise that 25ml would make the drops 0.2ppm. I knew that it's capable of 0.2ppm, but I didn't realise it was jut a matter of 15ml more water. The TF100 doesn't have that in the instructions and until now I've never used an FAS-DPD kit. The previous kit I used was from Leslie's and is their "deluxe" DPD test kit that costs $70 and uses Taylor chemicals. That's how I was able to convince the people running my HOA to get the TF100 kit since it was technically cheaper though the shipping made it almost $80.

The odor smells kinda like most public swimming pools that I've been to in the past. It is kinda like bleach vs chlorinated tap water though. It is not strong after adding chlorine so I'm not sure what it is if it's not CC.
I guess it might not be an issue then. Nobody has complained about any irritations either so we must be doing something right.

As for keeping chlorine at 4ppm or more, I'm trying...

I added chlorine on Sunday night(28th) and on Monday night(29th) equal to over three gallons between two days. Both times to bring the FC to 8ppm and by the next time I test it it's down again. We've been losing a lot of chlorine in one day too. At 8:45am on Tuesday FC=8,CC=0.5, by Wednesday 7:30am FC=2 with CC=0.5. That's a 75% drop in 24 hours.

I've been adding a gallon and a half of 10% chlorine almost every other day and either it's the heat (100+ for almost all of Aug.) or CYA is NOT as high as I'm thinking it is or both. We don't have a heavy bather load either. 5 people at a time max over the last few days and perhaps less since school is back in session here.

I dosed it on Sunday night before my original post as I said. And again that night with another gallon and 8-8oz cups. On Tuesday morning TC=8.5, FC=8, CC=0.5 ( finally read some CC by then), pH 7.8, I didn't check TA since pH didn't change from last reading.

By Today (Wednesday) the TC is down to 2.5 with FC=2 and CC=0.5, (Pool store got TC=2.5, FC=2 also)
TA=110(pool store test, I didn't test this myself), pH=7.8 I've been reading TA in the 170 range and last time around 130. Since I'd been adding muriatic I figured it was working with the 130 better than 170.

Maybe the pool store is using the CYA correction factor (whatever it's called) with their TA reading since they got 20 points lower than my last reading and I've not added any more MA since Sunday morning since pH has remained stable.

We had the pool store check for phosphates and they were >2000 so was used some phosfree (against my wishes but maybe it'll help). Maybe our source water is high in phosphates; it's very hard water. We've had to add some water in the last few days. We're in a mandatory water reduction here so we can only add water sproadically, but it was necessary to prevent the pump going dry.

I used cal hypo shock this time since my HOA wants to use up what we have on hand. They're still relying on pool store readings of CH which I'm reading to be 350. The pool store read 225. ARG! How can they mess up so simple a test?!

Anyway, I added 2lbs of cal-hypo 73% which should be enough to bring it to almost 10 (2 ppm more than FC should be) and since I dosed it at 10am allow for some to burn off. I'll check again in the morning (Thursday).

Sorry, it's late and I'm tired since I had to get up earlier than I ususally do.
I think I repeated my self a time or two here, but I'm also too tired to fix it.

[chem geek]

The TF-100 also uses Taylor chemicals. I didn't realize it didn't have the (alternative) 25 ml 0.2 ppm instructions. You can find those instructions here with the Taylor K-2006 that is similar to the TF-100 (but not as good a value since it has far less reagent for the FAS-DPD and CYA tests).

The phosphate remover will only be like insurance helping to prevent algae growth if the chlorine level got too low. It won't do much if you are maintaining the proper FC/CYA ratio. Anyway, it doesn't hurt -- except in the pocketbook.

[Henry_R]

The TF-100 also uses Taylor chemicals. I didn't realize it didn't have the (alternative) 25 ml 0.2 ppm instructions. You can find those instructions here with the Taylor K-2006 that is similar to the TF-100 (but not as good a value since it has far less reagent for the FAS-DPD and CYA tests).

The phosphate remover will only be like insurance helping to prevent algae growth if the chlorine level got too low. It won't do much if you are maintaining the proper FC/CYA ratio. Anyway, it doesn't hurt -- except in the pocketbook.

The PhosFree was a bonus thrown in by the pool store manager when we began this venture in July by buying something like $250-300 worth of chemicals (50lb cal-hypo, 25lb 3" tabs and algae remover) and pool equipment including a vacuum hose, head and pole. So for now it cost nothing for that and hwv only used it sparingly. I said phosphates were >2000,btw, but I here-tell it was only 200 so it might as well have been zero as long as chlorine is normal which it is though I'm getting complaints that I'm using too much chlorine. I've gone through 6-128 oz bottles of 10% chlorine since Aug 23rd. To people who *still* will not follow what I've said that looks like it's a lot and it seems costly. I know it's not since I've seen the cost analysis thread of costs of chlorine methods where cal-hypo and liquid come out within pennies of each other.