Bleach seems to be costing me 2x as much as tablets?

[Threxx]

Hi All - my first post here, although I've been reading the forums and help articles for nearly a year now (since before we broke ground on our 36k gallon gunite pool in TN). I also have the 'pool math' app and bought the big test kit everyone here recommends and use it at least once a week.

Anyhow... I just can't seem to make sense of using bleach instead of tablets. Maybe prices around me are out of whack?
Bleach: The cheapest I can find bleach anywhere is at home depot, where if I buy in bulk, at least 12 gallons of store brand 10% concentration, it costs $3.00/gal.
Trichlor tablets: I can get 80 tablets (half a pound per tablet) from Costco for $65. Or about $0.8125 per tablet or $1.625 per pound.

As best as I can tell, 1 gallon of bleach is equal to about 0.9 pounds of the tablets assuming the bleach is brand new. Realistically the stuff I'm getting off the shelf at home depot has often times been sitting there a while - and since I don't want to run by HD frequently, I also stock up and so the bleach may sit on my shelf for up to another month. Meaning by the time I use it, 1 gallon of bleach may only be equal to about .6 or .7 pounds of tablets.

So $3.00 in bleach ends, as far as I can tell, typically nets me the same chlorine input as $1.46 in tablets if I used brand new bleach, and possibly only $0.97-$1.13 in tablets if the bleach is 2-3 months old by the time I use it.

Over this summer is seems like about 1.25 gallons of bleach every other day is enough to keep my pool just barely above the minimum free chlorine level recommended for my current CYA (about 50). Or about 6 tablets per week stuck in the offline chemical feeder.

So while I've heard my chlorine inputs will go down in the cooler months (I'm not closing the pool, but... clouds, nobody swimming, etc), my summer time chlorine costs are about $57 per month using bleach, or $21.18 per month using tablets.

Now, I understand if I keep using tablets, my CYA levels will continue to rise, and eventually I will need to partially drain and refill the pool

Water here costs 41 cents per 100 gallons including sewer fees. So let's say I drain half my water (18k gallons). That's $73.80. Not cheap, but still not nearly enough to offset the savings of running tablets.

I know draining and refilling the pool is a 'hassle', but at least it's just a once in a long while thing.

Also while I was researching I noticed that bleach raises my pH, while tablets lower it... which reflects the results I've been experiencing. When running tablets I hardly ever had to add muriatic acid. But when using bleach I was having to pour in a quart or so of muriatic acid every week. Again, not the end of the world, but the cost and time adds up to where I don't really understand the appeal of using bleach, unless maybe my prices are unusual. Maybe the cost of water and/or tablets here is lower than normal?

 

[borjis]

Bleach doesn't raise ph that I am aware of. It is considered ph neutral.
But there are other factors that could be the reason.

The cost has definitely gone way up the last couple of years though.

 

[ajw22]

Cost Comparison of Chlorine Sources

I originally posted the following on another forum (I thought I also posted it here, but can't find it). First, I describe exactly what is in chlorinating liquid and bleach as far as we know. I'll use 12.5% chlorinating liquid as an example. This link is a typical example. Though they do not...

www.troublefreepool.com

 

[Texas Splash]

The best thing about this discussion is that you @Threxx have taken TFP concepts to heart which is exactly what we hope to see pool owners do. TFP isn't about you managing your water the same way I do, it's about knowing what works best for your pool based on all of those factors (chemicals used, their effects, daily/weekly chemical demands, etc). There are other pools across the country that utilize tabs/pucks quite often, either because of a limited swim season, lots of water exchange from seasonal rain, or like you - evaluated the costs of each and determined to ride it out and exchange some (cheap) water. As long as you know the pros & cons of each, you are free to do what's best for you.

By the way .... welcome to TFP!

 

[Chickinvic]

Bleach should not be raising your PH. Something else is doing that.

 

[ajw22]

Bleach should not be raising your PH. Something else is doing that.

If you test pH after you add bleach it may temporarily show high. Test pH before adding chlorine then don’t worry about it. The pH neutralizes over time.

 

[aeh0603]

I noticed that bleach raises my pH, while tablets lower it

Bleach should not be raising your PH. Something else is doing that.

While bleach is not the cause of raising pH, it does cause a false high pH reading when FC is over 10. Also, the pH will naturally rise from aeration etc. When using liquid chlorine, this rise is noticeable and will need to be counteracted by also adding muriatic acid to lower pH as needed. Conversely, trichlor tablets are acidic, so they lower pH, raise FC and raise CYA all at once. I believe this is what Threxx was referring to.

 

[Threxx]

Cost Comparison of Chlorine Sources

I originally posted the following on another forum (I thought I also posted it here, but can't find it). First, I describe exactly what is in chlorinating liquid and bleach as far as we know. I'll use 12.5% chlorinating liquid as an example. This link is a typical example. Though they do not...

www.troublefreepool.com

Interesting!

The prices they show there have trichlor tabs costing about 35% more than it costs me, and bleach costing around 20% less than it costs me.

Even with those price diffences, according to the math in this link, using 12.5% bleach costs about 30% more per unit of chlorine added to the pool. He goes on to say that savings is more than offset by the need to add washing soda to raise PH. However, since I'm having to add muriatic acid to lower my pH, the pH lowering effects of the trichlor actually has the opposite effect on my net costs... it means I'm not having to add as much muriatic acid.

Also it seems the article assumes that most 12.5% bleach is actually still 12.5% when we use it? I know in my case, per the charts I've seen posted here, my 10% bleach is probably more like 7 or 8% bleach on average as a few months may have passed since it was produced before it ends up in my pool.

 

[Threxx]

The best thing about this discussion is that you @Threxx have taken TFP concepts to heart which is exactly what we hope to see pool owners do. TFP isn't about you managing your water the same way I do, it's about knowing what works best for your pool based on all of those factors (chemicals used, their effects, daily/weekly chemical demands, etc). There are other pools across the country that utilize tabs/pucks quite often, either because of a limited swim season, lots of water exchange from seasonal rain, or like you - evaluated the costs of each and determined to ride it out and exchange some (cheap) water. As long as you know the pros & cons of each, you are free to do what's best for you.

By the way .... welcome to TFP!

Thanks for the welcome. That's good to know. I agree it's good to have a fundamental understanding of how things work so I can make my own educated decisions. It makes pool care so much less intimidating when I understand why something is happening and what my options are. I guess I just wanted to lay my thoughts out here for examination because I figured maybe there was something I wasn't considering.

 

[Threxx]

While bleach is not the cause of raising pH, it does cause a false high pH reading when FC is over 10. Also, the pH will naturally rise from aeration etc. When using liquid chlorine, this rise is noticeable and will need to be counteracted by also adding muriatic acid to lower pH as needed. Conversely, trichlor tablets are acidic, so they lower pH, raise FC and raise CYA all at once. I believe this is what Threxx was referring to.

To be honest I thought I read somewhere that bleach had a mild pH raising effect. I mean I think the pH of bleach itself is pretty high... like 12? But I suppose adding one gallon of a pH 12 liquid to a 36k gallon pool doesn't necessarily mean much in and of itself.
The only thing I do know for sure is I have had to add muriatic acid far less frequently when using tabs.

 

[ajw22]

To be honest I thought I read somewhere that bleach had a mild pH raising effect. I mean I think the pH of bleach itself is pretty high... like 12? But I suppose adding one gallon of a pH 12 liquid to a 36k gallon pool doesn't necessarily mean much in and of itself.
The only thing I do know for sure is I have had to add muriatic acid far less frequently when using tabs.

When you add bleach to raise the FC, the pH does go up a little. But, when the FC is consumed, that process actually lowers the pH. So the net effect is that bleach is basically pH neutral in the pool.

That's why I said to test pH before you add bleach and then don't worry about it.

 

[aeh0603]

To be honest I thought I read somewhere that bleach had a mild pH raising effect. I mean I think the pH of bleach itself is pretty high... like 12? But I suppose adding one gallon of a pH 12 liquid to a 36k gallon pool doesn't necessarily mean much in and of itself.
The only thing I do know for sure is I have had to add muriatic acid far less frequently when using tabs.

I would have to dig through the deep end forums for the exact scientific answer... I believe joyfulnoise is the one who has explained the chemistry behind it, complete with the formulas for how the reaction happens when liquid chlorine is added to water. It may have a very slight effect on pH (i don't recall), but I do know it's effect on pH is negligible in the application of pool maintenance.

I was just trying to explain a bit about why you saw the difference in pH behavior based on using liquid vs tablets for FC.

 

[duraleigh]

The cheapest way to apply chlorine and manage your pool is not what TFP is about. We teach you the nuts and bolts of pool water management so you can make your own, informed decisions.

You (and many, many others) may find TFP really does end up being the least expensive overall but our goal is to get you to understand how to manage your pool successfully. A crystal clear swimming season is yours if you are willing to apply the principles we teach.

 

[Texas Splash]

Oh, and before I forget ..... if you do chose to use tabs frequently throughout a pool season, keep in mind they are acidic and tend to lower pH a bit. May not be a big deal for you, but something to watch. The PoolMath tool and APP also help to make you aware of those effects as well. Have a great weekend.

 

[JoyfulNoise]

Make sure the tablets you are buying are pure trichlor (99%) and not "multi-part" tablets. Costco's tend to sell the tablets that are multi-component and include chemicals like baking soda, flocculants and, sometimes, metal algaecides. You want to stay away from that stuff because (A) you don't need any of the fillers, and (B) you get less trichlor.

Municipal water in my part of the country is about 2.5X more expensive than yours (COT Water charges roughly $9-$10 per 1000 gallons) and pools get very warm around here (my pool is still in the low 90's). So burning through a lot of tablets and having to exchange water frequently is more costly. However, salt-water chlorine generators (SWG's) are very common around here, so I don't use much liquid chlorine at all. Acid is cheap and so that's not really a factor.

As you have learned, there are many ways to manage pool water chemistry....

 

[holdup1time]

Hi All - my first post here, although I've been reading the forums and help articles for nearly a year now (since before we broke ground on our 36k gallon gunite pool in TN). I also have the 'pool math' app and bought the big test kit everyone here recommends and use it at least once a week.

Anyhow... I just can't seem to make sense of using bleach instead of tablets. Maybe prices around me are out of whack?
Bleach: The cheapest I can find bleach anywhere is at home depot, where if I buy in bulk, at least 12 gallons of store brand 10% concentration, it costs $3.00/gal.
Trichlor tablets: I can get 80 tablets (half a pound per tablet) from Costco for $65. Or about $0.8125 per tablet or $1.625 per pound.

As best as I can tell, 1 gallon of bleach is equal to about 0.9 pounds of the tablets assuming the bleach is brand new. Realistically the stuff I'm getting off the shelf at home depot has often times been sitting there a while - and since I don't want to run by HD frequently, I also stock up and so the bleach may sit on my shelf for up to another month. Meaning by the time I use it, 1 gallon of bleach may only be equal to about .6 or .7 pounds of tablets.

So $3.00 in bleach ends, as far as I can tell, typically nets me the same chlorine input as $1.46 in tablets if I used brand new bleach, and possibly only $0.97-$1.13 in tablets if the bleach is 2-3 months old by the time I use it.

Over this summer is seems like about 1.25 gallons of bleach every other day is enough to keep my pool just barely above the minimum free chlorine level recommended for my current CYA (about 50). Or about 6 tablets per week stuck in the offline chemical feeder.

So while I've heard my chlorine inputs will go down in the cooler months (I'm not closing the pool, but... clouds, nobody swimming, etc), my summer time chlorine costs are about $57 per month using bleach, or $21.18 per month using tablets.

Now, I understand if I keep using tablets, my CYA levels will continue to rise, and eventually I will need to partially drain and refill the pool

Water here costs 41 cents per 100 gallons including sewer fees. So let's say I drain half my water (18k gallons). That's $73.80. Not cheap, but still not nearly enough to offset the savings of running tablets.

I know draining and refilling the pool is a 'hassle', but at least it's just a once in a long while thing.

Also while I was researching I noticed that bleach raises my pH, while tablets lower it... which reflects the results I've been experiencing. When running tablets I hardly ever had to add muriatic acid. But when using bleach I was having to pour in a quart or so of muriatic acid every week. Again, not the end of the world, but the cost and time adds up to where I don't really understand the appeal of using bleach, unless maybe my prices are unusual. Maybe the cost of water and/or tablets here is lower than normal?

Sooo I've been having this thought myself too. Our pool was finished in mid June. I started out using trichlor pucks but switched to liquid chlorine. Since switching, I've noticed, as you have, my ph is always going high...I'm at work but will try to find the msds but I did one time and it said the Ph of the liq chlorine was 12. New plaster plus the Ph of 12 on liquid chlorine and I'm always adding muratic acid...31%....so all I'm having to add to my pool daily is liquid chlorine and every 3rd day, adding Muratic Acid. My TA has been very consistent using only the liquid chlorine method...it finally dropped from 80 to 70 the other day...no biggie....when I was using the Trichlor pucks, my TA was dropping slowly from 120 down to 80....I made the switch to liquid chl right about the same time my TA was 80....so over 2 months roughly my TA has only dropped from 80 to 70. When I was using Trichlor, my pool was brand new and was running the pump 24 hours a day for the first 30 days...that is what drove up my CYA from 50 to 80....now my pool pump only runs 6.5 hours a day. Also when using the Trichlor pucks, my Ph was not rising near as fast and once I had to add baking soda due to my TA dropping.

So to me it's either use liquid chlorine and constantly have to add muratic acid...or I use Trichlor pucks knowing I'll have to add baking soda to raise my TA....also, during the winter months, I'll have to lower and fill my pool once a month a bout 1 foot at a time and this will lower my CYA back to lower levels for the next swim season....honestly, adding baking soda is much cheaper and safer for personal safety than messing with muratic acid...not having to add liq chlorine manually everyday is also appealing. Not sure which way I'm going to end up going....for now, sticking with liq chlorine....but it's not hard to drain and fill my pool slowly over the 6 months it will be too cold to swim in....much easier than adding liq chl daily and adding muratic acid every 3 days.

 

[holdup1time]

Hi All - my first post here, although I've been reading the forums and help articles for nearly a year now (since before we broke ground on our 36k gallon gunite pool in TN). I also have the 'pool math' app and bought the big test kit everyone here recommends and use it at least once a week.

Anyhow... I just can't seem to make sense of using bleach instead of tablets. Maybe prices around me are out of whack?
Bleach: The cheapest I can find bleach anywhere is at home depot, where if I buy in bulk, at least 12 gallons of store brand 10% concentration, it costs $3.00/gal.
Trichlor tablets: I can get 80 tablets (half a pound per tablet) from Costco for $65. Or about $0.8125 per tablet or $1.625 per pound.

As best as I can tell, 1 gallon of bleach is equal to about 0.9 pounds of the tablets assuming the bleach is brand new. Realistically the stuff I'm getting off the shelf at home depot has often times been sitting there a while - and since I don't want to run by HD frequently, I also stock up and so the bleach may sit on my shelf for up to another month. Meaning by the time I use it, 1 gallon of bleach may only be equal to about .6 or .7 pounds of tablets.

So $3.00 in bleach ends, as far as I can tell, typically nets me the same chlorine input as $1.46 in tablets if I used brand new bleach, and possibly only $0.97-$1.13 in tablets if the bleach is 2-3 months old by the time I use it.

Over this summer is seems like about 1.25 gallons of bleach every other day is enough to keep my pool just barely above the minimum free chlorine level recommended for my current CYA (about 50). Or about 6 tablets per week stuck in the offline chemical feeder.

So while I've heard my chlorine inputs will go down in the cooler months (I'm not closing the pool, but... clouds, nobody swimming, etc), my summer time chlorine costs are about $57 per month using bleach, or $21.18 per month using tablets.

Now, I understand if I keep using tablets, my CYA levels will continue to rise, and eventually I will need to partially drain and refill the pool

Water here costs 41 cents per 100 gallons including sewer fees. So let's say I drain half my water (18k gallons). That's $73.80. Not cheap, but still not nearly enough to offset the savings of running tablets.

I know draining and refilling the pool is a 'hassle', but at least it's just a once in a long while thing.

Also while I was researching I noticed that bleach raises my pH, while tablets lower it... which reflects the results I've been experiencing. When running tablets I hardly ever had to add muriatic acid. But when using bleach I was having to pour in a quart or so of muriatic acid every week. Again, not the end of the world, but the cost and time adds up to where I don't really understand the appeal of using bleach, unless maybe my prices are unusual. Maybe the cost of water and/or tablets here is lower than normal?

Ok found the MSDS for the liq chl at Home Depot...Brand its HDX...msds shows the Ph is 12.5...look under section 9 "Physical and Chemical Properties" so I'm not sure why many here say liq chlorine is Ph neutral...to me neutral would be 7 ...unless I'm missing something. MSDS link is below
MSDS for Home Depot HDX Liq Chl

 

[JoyfulNoise]

The high pH of LC has nothing to do with pH rise. You are adding fractions of a gallon of LC to a body of water that contains tens of thousands of gallon. The pH rise from adding LC is minuscule. The cause/effect relationship is wrong.

The reason why pH rises in water is due to the outgassing of aqueous CO2 which is directly proportional to TA. If you have high TA, you will have high carbonate alkalinity which, in turn, means there is more dissolve CO2 gas in the pool water. As that CO2 outgasses from heat and aeration, a chemical equilibrium reaction happens and the pH increases. This happens all the time in surface waters open to the air.

The difference, as you note, is the source of acid used. If you use pucks, they are acidic and lower TA and pH. If you use liquid chlorine, it slightly raises pH but, over time, the pH decreases back to normal as the chlorine gets used up. So you need to add acid to a liquid chlorine sanitized pool because there is no longer a built source.

All of this is totally normal and expected. As long as you understand that water exchange is necessary with a trichlor-fed pool, then it’s fine to use it. The other key is that you have to test CYA more frequently to make sure that you are maintaining the correct FC/CYA ratio. As CYA increases, you must also increase your baseline FC level to ensure the water stays algae free.

 

[RMcGirr83]

If I understand correctly when liquid chlorine goes into the water, it actually won't raise the pH as much as you might think. Liquid chlorine's reactions create byproducts of both high pH (Sodium hydroxide) and low pH (Hydrochloric acid), which neutralize each other. The net pH change should be about zero.
@chem geek ?

 

[mguzzy]

I love it when these discussion pop up.. it really fleshes out how pool chemistry changes when various products are used to manage your pool, adjust your FC, etc.....

So @Threxx .. yes it appears the economics of your situation its cheaper to use tabs than LC. Your breakdown of the per unit cost is something everyone should do for their own pools. So follow that path! I figured it was cheaper to put in an SWG.. and that cost has worked out in my favor.. but I also include the amount of time I spent fussing with managing the pool chems, time to get them... etc. For me that is a calculable cost.. I bill hourly