Will using bleach for clorination raise the ph of my pool?

[jlbaker999]

I have been using bleach exclusively for a couple of years and pretty much got everything working right this year. The only thing I have to do besides keep the bleach adjusted (I have made an automatic bleach dispenser) is keep track of the CYA and the Ph. It seems that I have to add muriatic acid on weekly or bi-weekly basis to keep the Ph down to the 7.5 - 7.8 level. Why is this? Is it just a natural reaction of the bleach? Just curious.
I have a 13,000 gallon pool and have to add a quart to 1-1/2 qts of acid on a fairly regular basis.

 

[mknauss]

Sodium Hypochlorite added to your pool is pH neutral.

What is the TA of your pool water and fill water? Do you run the spillover on the spa for long periods? Higher TA and/or fill water TA can drive pH up, as well as aeration.

 

[thefloatqueen]

Everyone says it is pH neutral (and I am NOT disputing that!!!), but I did a little experiment and depending on the amount of LC, it did increase the pH fairly quickly (but NOT BY MUCH) with TA of 70 and no aeration. It wasn’t a significant increase, though. It increased by 0.1-0.2ppm for me. That was with 3 cups of 7.13% bleach. When I tried it with 1 cup of the same bleach, it did not make any difference.

EDIT: That was just MY personal experience! Not trying to give out any “false” information or start an argument. I’m just sharing my personal experiment I tried.

 

[mknauss]

If you test the pH of the pool water right after adding the LC, your pH will be raised slightly. But once the LC goes through its cycle of reaction, the overall result is pH neutral.

 

[gregsfc]

There are a couple of threads on here that you can find via a search with thorough explanations of the chemical process that occurs regarding sodium hypochlorite and its affect on pH if you like reading chemistry. The more simple answer is that bleach is pH neutral, but it goes up then back down as hypochlorous acid is produced as it sanitizes. If you've minimized excessive aeration already, lowering TA is usually the best solution. The easiest way to do this is to keep adjusting pH back down into range as you've been doing, but each adjustment should reduce TA, and eventually, TA should be low enough that the pH quits creeping back up. At that point, your TA should be at the right spot for your pool to help maintain pH. Don't raise it back up unless you're planning on using an acidic chemical like trichlor, which could cause a pH crash at your new, lower TA level. But if you take care of your own pool and use bleach, there is no risk of a crash.

My TA is 60. I use only sodium hypochlorite, aka bleach. I have no drift.

My first season using TFP methodolgies, I had to adjust TA from 90 down to 50 to better keep pH in range. Someone here had to explain to me that I should quit raising TA back up into the recommended range despite what was officially recommended (TA was recommended 70-100 back then on the TFP chart; now 50-90). The range is misleading. One may think any TA level within the published range is fine, but actually, your pool has its own sweet spot.

When I used trichlor, I needed higher TA to maintain in-range pH, because trichlor is acidic. For whatever reason, beginning last season, 60 became my new perfect TA level (no longer 50). According to the great ChemGeek, pools have different outgassing rates and different source waters, and therefore TA can be manipulated to help maintain pH levels.

Now If you're source water has super high TA, or you have aeration that you can't reduce as do those with generators, you may still have to continually make pH down adjustments. This forum has become mostly a salt water cell generator forum; those operators mostly have to dose with acid regularly due to the aeration caused by the generator; but many bleach users only rarely make pH adjustments. Many of us have a very trouble free pool adding only bleach and cya for pool care. Too bad our method has lost favor. Your method is the most trouble free of all, because you have auto injection.

 

[PoolGate]

Interesting, the 2 pools that i have added a lot of bleach at once to due to ammonia, all had very low ph when I was done. Perhaps that was a product of the ammonia neutralization?

 

[mknauss]

Perhaps that was a product of the ammonia neutralization?

Correct. That is a reaction of oxidizing the ammonia.

 

[JJ_Tex]

I'm no chemistry major, but 2 key points come to mind:

- Trichlor pucks are acidic, so a lot of people need to up the acid after switching from pucks to liquid chlorine
- My pool does not like to stay in the mid 7's very long at all, but will remain at 7.8-8.0 for days/weeks before I have to add acid. Try keeping it there vs constantly fighting it to keep in the mid 7's.

 

[Katodude]

- My pool does not like to stay in the mid 7's very long at all, but will remain at 7.8-8.0 for days/weeks before I have to add acid. Try keeping it there vs constantly fighting it to keep in the mid 7's.

Same here. My pool likes to be at 8. It will stay there for many days before it hits 8.1. But it wont even stay at 7.8 for very long.

 

[thefloatqueen]

If you test the pH of the pool water right after adding the LC, your pH will be raised slightly. But once the LC goes through its cycle of reaction, the overall result is pH neutral.

I tested it 30 mins after adding the LC. That makes sense, though! Good to know I’m not making my pH shoot up when adding large amounts of bleach (very rare).

 

[thefloatqueen]

Same here. My pool likes to be at 8. It will stay there for many days before it hits 8.1. But it wont even stay at 7.8 for very long.

Your fill water must have a high pH and alkalinity like mine does. When I tested my tap water, the alkalinity is 300 and pH is 8.0! Eeeek. That explained my pH bouncing around all summer since I was adding hose water often due to evaporation and long periods without rain.

 

[gregsfc]

I'm no chemistry major, but 2 key points come to mind:

- Trichlor pucks are acidic, so a lot of people need to up the acid after switching from pucks to liquid chlorine
- My pool does not like to stay in the mid 7's very long at all, but will remain at 7.8-8.0 for days/weeks before I have to add acid. Try keeping it there vs constantly fighting it to keep in the mid 7's.

Or keep TA lower than you would using pucks if you're not bound by strict csi limitations.

 

[mariane]

Or keep TA lower than you would using pucks if you're not bound by strict csi limitations.

@gregsfc Not to hijack the thread but my husband has relatives in Smithville.

 

[DanF]

One may think any TA level within the published range is fine, but actually, your pool has its own sweet spot.

Good post, @gregsfc. How do I determine what my pool's TA sweet spot is? Is it the level at which pH rise is lowest?
Note: I just installed an SWCG if that makes a difference.

 

[gregsfc]

Good post, @gregsfc. How do I determine what my pool's TA sweet spot is? Is it the level at which pH rise is lowest?
Note: I just installed an SWCG if that makes a difference.

Disclaimer; I'm not an expert. I was corrected by an expert about an assumption that I had made that SWCGs always results in a lot of upward pressure on pH. I developed that assumption via following a dozen threads or so where a pH drift delimma had been being duscussed; ways to reduce acid demand using an SWCG. Most-times there are three solutions proposed in threads I've read used in conjunction to minimize pH drift with SWCGs. One is to minimize run time of the SWCG while still maintaining sufficient FC. I can't comment any further on that strategy, as I've never even seen one, let alone operated one. Two is to let TA drop as low as 50 if necessary. I've read some threads where operators have let TA drop to 40. You do this by letting TA drop via adjusting pH into range each time it goes up out of range. Each dose of acid not only puts pH back in to range, but also slightly lowers TA. As long as you don't add soda, and your fill water doesn't have high TA, after a while, you should notice that the pH drift slows or even stops. This means that you're TA is at the sweet spot. Now for the precautions: Plaster pools must maintain a CSI range and so this method is limited. Could be other pool surfaces as well. Secondly, if you have high TA fill water or rain water, you're still going to fight pH and TA drift most likely. Thirdly, I'm no chemistry guru, but there is most-assuredly some sort of low TA limit that you can't go under lest you'll risk a pH crash and ruin equipment. I would think that adding cya or another acidic product would be the time you'd risk that phenomenon if your TA is too low. The last method I've read time and time again to reduce acid demand is to not adjust or maintain pH to the mid or low end of the acceptable range; rather try to keep it at the upper end and adjust it only when it drifts up to 8 or higher. Thst's been suggested in this thread as well. All I can say as a bleach user with a vinyl liner pool is that going from the Taylor recommended range of TA 80-120 when I first began following TFPC, down to the low end of the TFP recommendation, which is npwadays 50, totally solved my drift problem; and I don't even worry about reducing aeration or trying to shoot for the upper pH range of 7.8 techniques, because my pool stays right at pH 7.4 just by running my pool at a lower TA level than before. The only time I'll see a change in pH is if I add a significant amount of cya. It may then drop as low as 7.0 (hardly a crash), but about half the time that happens, the pH will recover on its own inside of a week. The other half of the time, I'll have to add just a touch of borax to get pH back in range. This is an average of once per year for me. There are others on here who have forgotten more than I know; maybe they'll chime in, but the great Chem Geek guided me on thos in 2014; and so I know that I'm golden with respect to the advice I received.

 

[gregsfc]

Oh one alibi please. One SWCG user on a previous thread actually floated one puck per week of trichlor to simultaneously control pH drift and maintain cya, as he also had quick cya degradation problem for whatever reason. This solved both issue for him; or at least reduced them greatly.