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

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,281
Tucson, AZ
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 ?
From this thread -

Adding Chlorine
NaOCl + H2O --> Na+ + HOCl + OH- (+ extra base Na+ + OH-)
HOCl --> H+ + OCl-

Sodium Hypochlorite (liquid chlorine or bleach) combines with water to produce sodium ions (part of regular table salt) plus disinfecting chlorine plus hydroxyl ion. The hydroxyl ion makes this a basic reaction that raises pH, but because the disinfecting chlorine is a weak acid this overall reaction raises the pH by less than a strong base would. Note that there is a small amount of extra base in the form of Sodium Hydroxide (lye or caustic soda) that comes with Sodium Hypochlorite and is there to help preserve it, but this amount is rather small.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
14,614
Evans, Georgia
The only pucks I saw for sale at Costco were the Clorox XtraBlue....which we all now know contain that dreaded Copper! Ugh!

So while they may be cheaper they can cost you more in the end when you have to later treat your pool for metal stains and buy special copper removal shampoos for your blond daughter's green hair. No bargain in my book.

Maddie :flower:
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,281
Tucson, AZ
Is there an definitive amount that adding liquid chlorine will raise pH? Say 2 cups will raise pH by x in a 10,000 gallon pool.
There is no simplistic answer when it comes to pH calculations because pH depends a lot on what chemical species are in that water that can buffer pH. Carbonates, cyanurates and borates all exist in solution and will modify pH calculations beyond simply accounting for a specific amount of hydroxide ion (OH-) added or taken away.

For example - at a pH of 7.5, CYA 50ppm, TA 80ppm, the addition of one gallon of bleach to 10,000 gallons of pool water will increase pH by +0.13. If you decrease the TA to 60ppm, the pH change is +0.17 and if you change the TA to 120ppm, the pH increase drops to +0.09. None of those changes would be particularly visible on a phenol red pH test. Pool Math use to call out the pH change when one added chlorine but because of programming limitations, it really was not accurate and it would confuse people who were trying to make FC adjustments to their water.
 
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holdup1time

Well-known member
Jun 15, 2019
77
Houston Texas
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.
Joyful,

Thanks for the chemistry lesson...so I've not had high TA since switching to Liq Chl months ago...it's been 80...I wouldn't think that is high TA...however, my pool is new plaster since mid June....I've heard new plaster pools generally have higher Ph...not sure if that is true but I just can't think of any other reason why my Ph is always so high...I have bubblers and water fountains but do not use them since I learned here that aeration raises Ph...so if I'm not aerating and my TA is not high, is my high Ph just due to new plaster? My backyard does get a great breeze through there all the time...could that wind across the pool water be a part of my high PH problem? Thanks :)
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,281
Tucson, AZ
In my opinion, 80ppm is high for any pool in the south/southwest. I routinely keep mine at or below 60ppm. Outgassing of CO2 happens in any body of water, aeration simply enhances it. Simply running a pool pump and causing the water to churn and mix is enough to drive outgassing; a good breeze helps a lot too. Fresh plaster can certainly drive up pH but a plaster surface should be fully carbonated (cured) after 6 months and not contribute much to the pH rise unless some chemical reaction is occurring that damages or compromises a plaster surface. I also add borates to my water to help buffer against pH rise but that’s an optional enhancement for pool owners.
 
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RMcGirr83

Gold Supporter
Nov 19, 2018
935
Tuscola, TX
FWIW our pool was completed in November of last year and I was constantly adding acid to get the pH in line (you can see it in my logs). Past few months I've only had to add acid on a weekly basis. Once pH hits 8 I lower to 7.5 or so and see ya next week.
 

beautifulpool

Silver Supporter
Jun 2, 2019
132
North TX
There is no simplistic answer when it comes to pH calculations because pH depends a lot on what chemical species are in that water that can buffer pH. Carbonates, cyanurates and borates all exist in solution and will modify pH calculations beyond simply accounting for a specific amount of hydroxide ion (OH-) added or taken away.

For example - at a pH of 7.5, CYA 50ppm, TA 80ppm, the addition of one gallon of bleach to 10,000 gallons of pool water will increase pH by +0.13. If you decrease the TA to 60ppm, the pH change is +0.17 and if you change the TA to 120ppm, the pH increase drops to +0.09. None of those changes would be particularly visible on a phenol red pH test. Pool Math use to call out the pH change when one added chlorine but because of programming limitations, it really was not accurate and it would confuse people who were trying to make FC adjustments to their water.
Joyful noise, this explains a lot.
Everyone is reposting my comment LC Can raise pH” What I didn’t add was the whole summer using TFP’s method which is successful for me, I ALWAYS add 1/2 dose required for the change I want, then make myself wait 24 hours and re-test. Often, I find no need to add the remaining 1/2 dose. Thank you for your post... if I’m following your post and this chemistry correctly, the pH if tested later rather than earlier (after adding LC) will show less of change
.... if I’m following you correctly, and this explains why.....
...can I ask you another “chemistry” question. I could post in the “deep end”
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,281
Tucson, AZ
Joyful noise, this explains a lot.
Everyone is reposting my comment LC Can raise pH” What I didn’t add was the whole summer using TFP’s method which is successful for me, I ALWAYS add 1/2 dose required for the change I want, then make myself wait 24 hours and re-test. Often, I find no need to add the remaining 1/2 dose. Thank you for your post... if I’m following your post and this chemistry correctly, the pH if tested later rather than earlier (after adding LC) will show less of change
.... if I’m following you correctly, and this explains why.....
...can I ask you another “chemistry” question. I could post in the “deep end”
Detailed chemistry questions are best posted in The Deep End sub-forum. Like making sausage, most folks care not to see the gory details but rather just enjoy the end-product...
 

iflyjetzzz

Well-known member
Jun 16, 2011
79
Las Vegas, NV
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 ;)
The downside of tabs is that one's CYA gets too high after a season of tab usage.

As for a SWG, we had a SWG installed on our new pool in Las Vegas (VERY hard water). In order to keep the SWG in good shape and keep from getting calcium stains, I had a plumber have soft water plumbed to my pool autofill. The SWG works flawlessly and when I've checked for any buildup inside the SWG, it's been as clean as brand new. (My CH is stable ~420)

Since going with a salt water pool, my wife has been much happier with the water; less skin problems. My maintenance is MUCH LOWER than on our previous two non-SWG pools. Our pool is now almost completely trouble free, with only needing to add some muriatic acid for balancing the chemistry.
I figure that I should be able to get more than a decade out of my SWG based on the 10,000 hr lifespan - I have an automatic pool cover and have found that my pool stays crystal clear and the chlorine levels are fine when I run the pump for ~1.5hrs/day in winter and ~3hrs/day in summer.
I'm also no longer concerned about algae growth in my pool when I'm away from home for more than a week.

Like you, I have nothing but praise for the switch to a salt water pool. It has significantly reduced my pool maintenance time and cost.
 

mguzzy

Gold Supporter
Jul 8, 2015
2,332
OV, CA
The downside of tabs is that one's CYA gets too high after a season of tab usage.

As for a SWG, we had a SWG installed on our new pool in Las Vegas (VERY hard water). In order to keep the SWG in good shape and keep from getting calcium stains, I had a plumber have soft water plumbed to my pool autofill. The SWG works flawlessly and when I've checked for any buildup inside the SWG, it's been as clean as brand new. (My CH is stable ~420)

Since going with a salt water pool, my wife has been much happier with the water; less skin problems. My maintenance is MUCH LOWER than on our previous two non-SWG pools. Our pool is now almost completely trouble free, with only needing to add some muriatic acid for balancing the chemistry.
I figure that I should be able to get more than a decade out of my SWG based on the 10,000 hr lifespan - I have an automatic pool cover and have found that my pool stays crystal clear and the chlorine levels are fine when I run the pump for ~1.5hrs/day in winter and ~3hrs/day in summer.
I'm also no longer concerned about algae growth in my pool when I'm away from home for more than a week.

Like you, I have nothing but praise for the switch to a salt water pool. It has significantly reduced my pool maintenance time and cost.
Right, Tabs add CYA.. but it depends on the kind of Tabs... Also it works for some people that get a lot of summer showers so they are getting naturally diluted...

I can't agree with you more on the SWG. well said.. And good idea on the autofill.
 

iflyjetzzz

Well-known member
Jun 16, 2011
79
Las Vegas, NV
Right, Tabs add CYA.. but it depends on the kind of Tabs... Also it works for some people that get a lot of summer showers so they are getting naturally diluted...

I can't agree with you more on the SWG. well said.. And good idea on the autofill.
I live in Las Vegas - what is this 'summer showers' thing you mention?? :p
I thought that CYA is like calcium in the water - it doesn't dissipate with evaporation. And I'd assume that rainfall is very close to simply refilling the pool, except that rainwater will lower your pH and alkalinity. Perhaps I misunderstood CYA - I thought that partial pool draining was the only real way to lower CYA in pools.
I confess that I haven't tested my CYA since spring - I have an automatic pool cover so my water doesn't get exposed to sunlight unless someone's in the pool. I'll have to check my CYA level today to compare with spring.

As far as a SWG, my understanding is that calcium deposits are the big killer, hence the reason why I always mention having soft water plumbed for the autofill on salt water pools in areas with hard water. The biggest complaints I've heard about salt water pools are 1) the water is 'too slippery'. My water's at ~3500 ppm and it doesn't feel 'slippery' - my house (soft) water feels 'slippery' when I take a shower, but I don't notice it in my pool, and 2) people are concerned with salt stains/damage to their decking. I've chosen a crushed coral decking that's off white so I'm not concerned about any staining. Any long term damage is more than offset by how quick/easy it is to maintain my pool vs previous non-salt water pools.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
19,758
Northern NJ
Perhaps I misunderstood CYA - I thought that partial pool draining was the only real way to lower CYA in pools.
CYA degrades from high water temperature. This tends to show in water temperatures of 90+ degrees. Every 10F increase in temperature results in roughly doubling the rate of degradation. Read...

How_is_CYA_Lost_and_Degrade_in_Pool_Water?
 
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mguzzy

Gold Supporter
Jul 8, 2015
2,332
OV, CA
@iflyjetzzz for you.. If you don't get any natural rainfall that would force you to drain your pool.. you would have to do a drain an refill to lower your CYA and Ca. I get lots of rain in the winter so I have to add CYA every spring to make up for the dilution. If you live in other parts of the country that get summer rains.. then the dilution is ongoing. Also CYA does degrade over time, but not as fast as most people contribute to it with pucks.

Yes Calcium scaling can impede the performance of the SWG. so its a good idea to test your incoming water and see whats there. I've never heard the too slippery complaint in a salt pool, most people like the "satin" feel. And in the almost 15 years I've had my SWG I've not seen any staining or salt damage. Almost always, the anecdotal claims of salt damage are due to other chemistry issues.
 

iflyjetzzz

Well-known member
Jun 16, 2011
79
Las Vegas, NV
CYA degrades from high water temperature. This tends to show in water temperatures of 90+ degrees. Every 10F increase in temperature results in roughly doubling the rate of degradation. Read...

Awesome link! Thanks much - it looks like my CYA fell slightly since Feb - from 40 to ~30. That's still in acceptable range, from my IC40 (salt water generator) manual. I will bring it back up to 40-50 range. I know that number is much lower than TFP recommends for salt water pools but since my pool's mostly covered, I keep the CYA lower so that I can keep the chlorine level a little bit lower.
 

mguzzy

Gold Supporter
Jul 8, 2015
2,332
OV, CA
What Allen said!
Also, rather than follow the "manual" I suggest you tinker more with your CYA and see what works best for your pool. I found mine works best at around 60 and not as well at 40. Everyone's pool is different; different physical setting, different water source, etc. So it no surprise the chem is different too.
 

iflyjetzzz

Well-known member
Jun 16, 2011
79
Las Vegas, NV
What Allen said!
Also, rather than follow the "manual" I suggest you tinker more with your CYA and see what works best for your pool. I found mine works best at around 60 and not as well at 40. Everyone's pool is different; different physical setting, different water source, etc. So it no surprise the chem is different too.
This was my first summer with the new pool. The low (40 at start of season down to 30 now) CYA level has worked fantastic for me. I run the SWG at 100% and run my pool pump for ~3hrs/day during summer and have now dialed it back to 2hrs/day. I will likely choose a lower daily time for running my pool pump as winter progresses.
Keep in mind that I have an automatic pool cover that does not allow sunlight to reach my pool when it is closed, and it is closed unless the pool is in use. That also allows me to not run the pool pump as frequently, as very little debris gets into my pool.
 
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santacruzpool

Gold Supporter
Feb 24, 2015
740
Santa Cruz, CA
I also run my mostly covered pool with a CYA between 30-40 - it works well for the special case of a having the pool closed the majority of the time by the opaque automatic safety cover.