Cost Comparison of Chlorine Sources

[chem geek]

bbse,

This link has a table near the bottom of the webpage that shows that the half-life of more concentrated chlorine isn't very long. At 12.5% and 80F temp, the half-life is around 150 days (5 months) so it really needs to be used within a month or two to be economical. If you can keep it at cool temps, then that helps a lot.

Richard

[gonefishin]

bbse,

This link has a table near the bottom of the webpage that shows that the half-life of more concentrated chlorine isn't very long. At 12.5% and 80F temp, the half-life is around 150 days (5 months) so it really needs to be used within a month or two to be economical. If you can keep it at cool temps, then that helps a lot.

Richard

Hi Richard

5 gallons of 15% will cause a theoretical raise of 75ppm in a 10,000 gallon pool. 5 gallons of 14% 70. 5 gallons of 12% of 60ppm . 5 gallons of 10% 50ppm raise. 5 gallons of 8% 40ppm. 5 gallons of a 6% solution 30.

I've still got to fill my 5 gallon carboy with the greater than 12% solution. But when I do I plan to get a sample and see what real world measurements would be like.

So if you have a daily consumption rate of 1.5-4ppm then you end up using 5 gallons of 12% solution up in 40 days or shorter. I would imagine utilizing a solar cover could increase the length of time that you'll have your 12% bleach around.

But even if you kept the 12% around for 5 months (to reach the half life that you stated at 80f) wouldn't you still end up somewhere around 45ppm increase for 5 gallons over 5 months? Which would round out somewhere to a near equivalent of 9% (ish) over 5 months for a starting 12% solution.

But I thought that bleach was supposed to become more stable with every bit that it weakens. (Where) if you start with a 12% solution it will take longer to degrade from 12% to 11% than it would from 6% to 5%...and also the same would hold true from 11% to 10%, no? (I'm just thinking aloud here...and asking questions so I can understand a bit better) If this is true...then wouldn't it be difficult to predict how much a 12% solution would degrade over 3 months?

(if the above is true) Wouldn't the rate at which bleach weakens actually increase (in length of time) for each percentage loss. I would think that this would give you a slightly better cost/effect ratio even if it were drawn out to the 5 month time period. Now, if you used up the 5 gallons in three months I would think it would even increase more.

just thinking aloud
thanks,
dan

[gonefishin]

I also found this posted by a Clorox Product Specialist

We recommend storing our bleach at room temperatures. It can be stored for about 6 months at temperatures between 50 and 70 degrees Fahrenheit. After this time, bleach will be begin to degrade at a rate of 20% each year until totally degraded to salt and water. Storing at temperatures much higher than 70 degrees Fahrenheit could cause the bleach to lose its effectiveness and degrade more rapidly. However, if you require 6% sodium hypochlorite, you should change your supply every 3 months

So at 50-70f the 6% solution would hold it's rate for approx 6 months. So it would degrade 1.2% that first year and a half and .94% in the year after that. So the 6% solution would be 3.84% after 2 1/2 years.

I think that this just drives the point (I think orginally brought up by CarlD?) that the greatest savings can be had if you purchase a 12% solution and then dilute it to half that strength for storage of that bleach until you can use it in the pool. If you need to...dilute the 12% bleach in old bleach bottles to keep on hand. Also...ask your bleach supplier how often they test their bleach, how often they receive deliveries in a month.


thanks chemgeek!
dan

[chem geek]

Yes, you are right. Diluting the concentrated solution in half will significantly extend its life. It is also correct that as the chlorine breaks down its rate of breakdown will slow down, but note that the half-life takes that into account -- the table isn't a rate table but the time it takes to get to half of its strength and accounts for this slowdown. I use 12.5% chlorinating liquid and don't run into any problems even after a month or two which is about how long it takes me to go through 4 gallons, but the temp in storage is around 55-60F at night and 75-80F during the day.

Richard

[chem geek]

Just wanted to bump this since I added the costs of adjusting the pH for Trichlor and Dichlor which are both acidic when accounting for chlorine addition AND consumption. This makes these sources of chlorine quite a bit more expensive then Cal-Hypo and bleach and chlorinating liquid.

[Spensar]

Thanks for the post. I can take my local prices and figure out my value pretty quick.

Though bulk 12.5% chlorine is $2.05 per gallon ($2.27CDN) here to fill either either a 10 litre or 20 litre carboy, much cheaper than the $3.25 per 1 gallon in the calcs, so I don't think the other sources will be able to touch it.

[Tredge]

Yes, I bought 80lbs of Trichlor at Sam's last year but it has stabilizer in it at since my pool is already up to nearly 70 ppm of CYA, I want a source of chlorine that does not have CYA added to it.

Doing the same here. Due to the SWG I need the -PH from the Trichlor and my CYA is low after every winter.

I use trichlor sparingly for extra boosts in chlorine and when CYA or Acid needs a bump.

Consider the cost of Acid and Stabalizer the Trichlor really works out to be a great value in my situation.

I think as long as you keep an eye on your PH and CYA the trichlor is a clear winner.

[steveinaz]

Dont know if this helps the cause, but the 2 methods I used cost:

Bleach...$12-$14 a month (Clorox)
SWCG...$4.00 for 20lbs of replacement salt (season)

[Themadczar]

There is a simple calculation to see if the sale price of bleach at one store is better than what you normally pay for bleach...
Price/ounces/% chlorine. For example, i can get a gallon of 6% bleach at Aldi for $1.21. Price per oz of CL is $1.21/96/.06 or $0.21/oz. When Walmart had 3 oversize jugs (128 oz each) of 8.25% bleach on sale for $8.65 I needed to know if this was a better deal. So, 8.65/(128x3)/.0825 = $0.273/oz. Aldi is still the better deal. A simple calculation you can do on your smart phone in a few seconds to ensure you are buying the cheapest chlorine around!