Info from Clorox on using their bleach for pools

[waterbear]

In the meantime, I did some quick research at some stores today and found that bottles of Clorox Regular bleach say 6.0% Sodium Hypochlorite and below that it says 5.7% available chlorine.

Richard

Interesting....I just looked on the new jug of Regular Clorox in my laundry room and it, too, says 6% and I also looked at a jug of generic bleach from Ace Hardware and it says 5.25%. I also remember the older jugs of Regular chlorox used to say 5.25%. I wonder if Clorox has bumped up the strength of their bleach a bit so it 'whitens' better? The store I work at sells 'liquid chlorine' in both 10% (HTH brand gallons) and 12.5% (The carbouys we fill from our tank). The 12.5% is supposed to be around 14-16% when delivered, according to the company we get it from, to compensate for the loss of strenth on storage.
The plot seems to thicken the deeper we dig........

[chem geek]

Yes, it does appear that Clorox increased their Regular concentration from 5.25% to 6.0% at some point in time so that 5.25% is now the generic brand concentration.

Additional inconsistencies abound. The chlorine I get from my pool store which comes in gallon plastic jugs labeled Sani-Clor and manufactured by Hasa, says on the bottle that it has 12.5% Sodium Hypochlorite as the active ingredient, but it also says that 3-1/4 quarts added to 10,000 gallons increases chlorine by 10 ppm. This latter calculation only makes sense if 12.5% is a Trade %. The $2.50/gallon price is just for the chlorine. The gallon jugs come 4 to a plastic case and there is a deposit per bottle ($0.50 I think) and case ($1.00 or $2.00 I think), but since I always just exchange one case with 4 bottles for another my effective cost is just the $2.50/gallon plus a tiny amount of interest I'm losing (by not investing) on the $4.00 total deposit.

On the other hand, I found Kem-Tek 10% chlorinating liquid that claims 10% Sodium Hypochlorite and it says that 11 ounces in 10,000 gallons yields 1 ppm which only makes sense if 10% is a Weight % of sodium hypochlorite and even then 12 ounces would be more accurate.

So what's the bottom line? It appears that the manufacturers are not consistent. Combine that with the loss of chlorine over time and this means you can really only know what you are getting by testing it, either through a straight dilution test or by testing your pool before and after a significant addition (waiting an hour). Picky, picky, picky...

Richard

[medvampire]

We use to have to test each lot and shipment of chlorx coming in to the hospital by spec gravity. We used a refractometer and had a chart that would allow us to get a 6000 ppm dilution for sanitizing surfaces. We logged each test and the variances would astound you even with in lot test. The hospital where I work doesn’t test due to the HIV scare is winding down. Like Richard mentioned you may have to test each time.
Steve

[fcfrey]

Since I am now injecting a bleach solution with a pump I test every batch I mix up. Today I over-shot on the pumping rate so I decided to mix a weaker concentration. I put one 182 oz bottle of Clorox with two 182 oz bottles of pool water to make what I would have thought to be a ~2% solution. When I tested it ---- it was 3.2% ---- repeated the FAS-DPD test and got the same thing??????? ??????? I did not test the bleach before I mixed it.

My pool water was 7.3ppm but that's a long way from the 6% ?? bleach that it was mixed with.

[chem geek]

Your 3.2% one-third diluted measurement doesn't make sense, even for Clorox Ultra. I don't know what to say. Perhaps try diluting it directly next time. And you are right that your pool water should have minimal effect on the final measurement since it is has so much lower chlorine level than the 6% bleach.

[fcfrey]

I tested bleach and my injection solution again today and found the Clorox Ultra I bought from Sams is running about 7.2% by FAS-DPD test. What I can't figure is that a 1 to 3 (bleach to water) dilution is still testing at 2.4% solution for my injection pump. Does this compute??? (maybe it's this "new math" )

[chem geek]

I tested bleach and my injection solution again today and found the Clorox Ultra I bought from Sams is running about 7.2% by FAS-DPD test. What I can't figure is that a 1 to 3 (bleach to water) dilution is still testing at 2.4% solution for my injection pump. Does this compute??? (maybe it's this "new math" )

Well 2.4% is a lot closer than the 3.2% you reported earlier. When you say "1 to 3" do you mean 1 volume of bleach in 3 volumes of water or do you mean 1 volume of bleach into 3 total volumes (i.e. 2 volumes of water)? You are right that starting with 7.2% and truly diluting 1 part plus 3 parts water (a 25% dilution) should yield 1.8% and not the 2.4% you are getting. On the other hand, if you were doing 1 part into 3 total (so 1 chlorine and 2 water), then this would be a one-third diultion which should get 2.4% which is exactly what you got. So either there is something really screwy or your 1 to 3 wasn't 1 part bleach and 3 parts water, but was 1 part bleach into 3 total parts (2 parts water).

Perhaps if you explain how you did the 1 to 3 dilution this might clear things up.

Richard

[KurtV]

Aren't these home-brewed tests of chlorine strength hopelessly inaccurate? Aren't the errors inherent in diluting a sample to this level simply huge?

We tell people to dilute water samples by 3 or 4 to 1 so they can test higher chlorine levels with an OTO test but then warn them that the results are just ballpark. Now people are diluting chlorine samples by 20,000 to 1 (or so) and talking about tenths of a percent precision? I dunno...

[chem geek]

Aren't these home-brewed tests of chlorine strength hopelessly inaccurate? Aren't the errors inherent in diluting a sample to this level simply huge?

We tell people to dilute water samples by 3 or 4 to 1 so they can test higher chlorine levels with an OTO test but then warn them that the results are just ballpark. Now people are diluting chlorine samples by 20,000 to 1 (or so) and talking about tenths of a percent precision? I dunno...

You are right that unless one uses a calibrated pipette, the errors will be quite large. However, having a large dilution ratio does not contribute to the error. An error in a ratio, which is what a 20,000 to 1 dilution is measuring, is only equal to the percentage or proportionate error in the numerator and denominator. If the "1" unit were one drop and this was only accurate to within half a drop, then this is a 50% error and is huge, but if the "1" unit were 1 ml and were measured in a calibrated pipette, then the error could be as low as 1%. The "20,000" large volume can be fairly easily measured to within 1%, again assuming one has an accurate large volume measuring tool (for liters or quarts, for example).

I'm not sure how fcfrey is doing the measurements, but you bring up a good point about accuracy. The easiest way to determine the rough accuracy of a measurement is to try and repeat the measurement and see if you get the same result, especially if you go on the low/high side for the small/large volume measurement and then repeat going on the high/low side.

Richard