Seeking input on using 68% Cal Hypo vs. 12.5% Bleach to add FC

[JPMorgan]

I was doing some math and came up with the following calculations on cost of Bleach vs. Cal Hypo for adding FC to my pool:

12.5% Bleach: 20 oz. raises FC by 1 ppm. Cost $4 per gallon. Cost per 1 ppm FC = $1.60

68% Cal Hypo: 4 oz. raises FC by 1 ppm Cost $100 per 25 lbs (400 oz.) Cost per 1 ppm FC = $1.00

So... at the prices noted above for bleach vs. cal hypo, I am saving 60% by using cal hypo.

Now, I know cal hypo will also raise my CH ( about .7 ppm for every 4 oz of 68% cal hypo) so I would have to keep an eye on that. However, I am usually adding 1-3 inches of water per week to my 20k pool, so I assume CH is always dropping a bit with the fill water and/or rain water.

Because of the significant difference in price, I'm thinking that it makes sense to use cal hypo to chlorinate my pool until my CH is approaching the upper limit recommended by TFP (350 ppm). (Right now I am at 270 ppm on CH.) I might even be able to get through a whole season (about 4 months here in Chicago) using cal hypo if I start the season with CH at 250 or lower, which I think it should be after first filling the pool for the new season.

I would greatly appreciate any comments form the TFP experts on my calculations and/or plans to use cal hypo as primary means of chlorinating.

BTW..... I didn't even figure into the equation the cost of purchasing calcium hypochloride separately to add CH to the pool when needed.

 

[JoyfulNoise]

It’s fine to use cal-hypo as you’ve noted the issues with it (raises the CH) and you’re aware of them. However, topping off does not change CH at all - CH only decreases when water is physically removed from the pool and replaced with fresh water that has lower CH. So rain water can lower CH if you drain first or if the pool overflows.

Just note that cal-hypo is best added to a pool by first dissolving it in a bucket of water and then slowly pouring it in front of a return or dispensing it around the edge. Then you should brush well to make sure any remaining solids are mixed in. You can expect the cal-hypo to cause temporary cloudiness that should go away with filter and it will raise pH as it adds caustic hydroxide and carbonates to the water. So you’ll need to keep an eye on pH, TA and CH in order to rebalance as-needed.

 

[cfherrman]

Unless your fill water is on a water softener, your ch will raise from topping up. Your ch fill water needs to under 200 for this to be more of a permanent solution.

Walmart has 6% for $1.77, 42 oz is 1 ppm, or $0.59. 1 jug does 3 ppm and weights 8 lbs. This is a permanent solution for every pool

 

[JPMorgan]

Ooops....I just realized my mathematical error above. I was dividing doses by cost (6.4 "doses" of 1 ppm FC in 1 gal of bleach divided by $4 = $1.6)

However, I should be dividing cost by doses to get cost per dose. $4 divided by 6.4 doses of 1 ppm FC = $.625. The cost per dose of bleach is about 62.5 cents.

For cal hypo the math is as follows: $100 divided by 100 doses of 1 ppm FC = $1 per dose.

The bleach is actually about 38% cheaper.

However I can get 50 lbs of cal hypo for $150 in which case the math is: $150 divided by 200 doses of 1 ppm FC = $.75 per dose.

Bleach is still the winner by about 17%.

Makes sense to use bleach for chlorinating unless you have some unused cal hypo from your pre-TFP days (which I did this year).

 

[doc8404]

Unless your fill water is on a water softener, your ch will raise from topping up. Your ch fill water needs to under 200 for this to be more of a permanent solution.

Walmart has 6% for $1.77, 42 oz is 1 ppm, or $0.59. 1 jug does 3 ppm and weights 8 lbs. This is a permanent solution for every pool

Nice. My Walmart is $2.27 for that same gallon!

 

[getreal720]

My walmart is also well over $2 a gallon for the regular 6%. I bought my last bleach at $2.20 a gallon for 6% at the local dollar store.

You are way overpaying for that 68% cal-hypo. You can get a 50 pound bucket online for less than $100 with taxes and shipping.
I drug my feet on it, and didn't buy that same 50 pound bucket for $65 on line about six weeks ago. I don't use it, I did last season
and my parents still use the cal-hypo. So... yeah. That's also a 50 pound bucket of 73%

In 10,000 gallons of water, adding 16 oz of 73% cal-hypo will give you 8.7 ppm FC
In that same 10,000 gallons of water, adding 180oz of 6% bleach will give you 8.7 ppm FC

The 16oz of 73% cal hypo will cost $1.84 (at 92$ for a shipped 50 pound bucket)
The 180oz of bleach will cost $2.48 (at 1.77 a gallon) or $3.09 at (2.20 a gallon)

The 16oz of 73% cal hypo costs $1.32 (at 65$ for a shipped 50 pound bucket).

If you watch online, usually in early to mid June, you can find 50 pound buckets of
73$ for usually $80 or under.


I only stopped using it because in my above ground pool, I have a vinyl liner and because
of the previous owners maintenance habits and/or the fact the pool was closed two seasons
with water in it, my liner became very wrinkled on the bottom.

This caused the cal-hypo to precipitate a bit, and particles would settle to the bottom. Even
with the pump running, they would still sit. Unless I physically brushed every day, they would
accumulate and stain my liner. Well, the liner is wrinkled and stained now and I hated spending
20 to 30 min daily brushing. This was even WITH me predisolving the powder and adding it in
front of the return jet.

I just switched to bleach. I have a somewhat short swim season. Bleach is a lot easier. But if
you don't have the issues I do, Cal-Hypo can be crazy cost affordable if you buy it right. Just
gotta keep that CH level in check.