pH keeps creeping up

[chem geek]

My question to Frank and Jakebear would be whether you have any water aeration features in your pools, such as waterfalls, spillovers (negative edge or pool/spa combo), fountains, showers, aerating jets, etc.? Also, Jakebear uses a bleach pump, but what source of chlorine does Frank use (SWG or bleach/chlorinating liquid)? Are you having a lot of rain (the splashing of raindrops provides a lot of aeration)? Are there any chemicals you are adding to your pools other than chlorine and acid?

As was pointed out, increasing the TA level only makes the problem worse and would require you to add more, not less, acid over time. With your vinyl liners, you can lower your TA level to 50 ppm without a problem and should find some improvement. Also, setting a target pH of 7.7 instead of trying to fight to maintain a lower pH will also help (for Frank, I would try that before lowering the TA further from 70; for Jakebear, you can certainly lower your TA to 70, see how it is, or lower it further to 50 as needed). Turning off water aeration features (if possible) will help. Using a pool cover should also help.

Adding Borates should reduce the frequency of acid addition (i.e. it will take longer for the pH to rise), but will not change the amount of acid you need to add over time (i.e. you will need to add more acid less frequently for the same net acid/time result to bring the pH back down). The main advantage of the Borates is that it gives you an additional pH buffer so that you can lower the TA level even further than you would normally do if the Borates weren't present. Note, however, that the borates do not have much capacity to handle a drop in pH so with low TA you need to be careful about any acid addition beyond that which you carefully monitor -- for example, CYA is acidic and Trichlor is very acidic.

This chart shows the relative carbon dioxide outgassing rates at various TA and pH levels. This is proportional to the quantity of acid you need to add per time. It is not an absolute amount since that depends on the amount of aeration, whether the pool is covered, wind, etc. This chart shows the relative rate of pH rise at various TA and pH levels. Though a lower TA significantly lowers the rate of outgassing, it is also less of a pH buffer so these somewhat balance out though the net result is a lessening of pH rise. You can see that going from 70 to 50 will help just a little, but maintaining a higher pH of 7.7 helps even more.

Richard

[Jakebear]

Hi Richard, We love your commentary an knowledge.

DH is fcfrey, you two have kicked around a lot of emails over the last year and we have learned a lot from you (and others too).

We have a fresh water pool with a pump like they use on a dialysis machine. He rigged it so the pump runs whenever the pool pump runs. It works well but he says he might have to add an acid pump to it??????

Any way we have had about 2" rain as thunderstorms over the last 2 weeks which has kept up with evaporation and rug rat splash out. Since we have a DE we do not back flush very often (just bump). There are no fountains etc. We have not added anything other than chlorine and acid for 6 or 8 weeks except a bit of CYA (DH wants it up to around 30 to try to cut chlorine consumption a bit)

We do not have trouble with TA ---- Just the pH. It's not a big deal but since I don't have to lug jugs like last year -- maybe I'm getting lazy. Either way all last year on BBB (before the chlorine pump) we never had to add acid so I'm wondering ------ was-sup????

[Jakebear]

DH informed me I showed an incorrect amount of bleach being injected. It is actually only about 10 oz of 6% --- the pump pumps 20 oz/hour but the concentration is only 3% since he cuts the 6% 50/50 with pool water. Thought that might be important to correct. He says it amounts to about 1.8 ppm per day loss???

[chem geek]

Jakebear,

A daily 1.8 ppm FC loss in a 27,000 gallon pool is not at all unusual nor high. In fact, with the CYA as low as 22, the loss could readily be higher if your pool gets exposed to more direct sunlight. I used to think that running a pool at the lowest CYA you could while keeping the FC at the appropriate minimum level was the way to go, but recent analysis and experiments (starting around here in a thread in the TroubleFreePool forum) has me now believe that higher CYA protects chlorine more than the traditional industry chart would indicate. So maintaining a higher CYA with higher FC should actually result in a lower chlorine loss so I not only agree with dcfrey, but you could go even higher and probably see even more benefit (seems almost weird to give advice that is 180 degrees from what it used to be, but I can't argue with reality). The CYA to FC ratio should be around 8.6 as a target (or lower) which puts it in the middle of Ben's Min/Max columns and corresponds to the 0.05 ppm disinfecting chlorine level in this chart.

Of course, I've avoided your rising pH issue and we now need to tackle that. There is no question that the rain would lead to a LOT of pH rise, but it sounds like you may have been experiencing this rise even before the rain hit. Perhaps the TA level is higher than last year, or there is more wind, or something else is going on. I doubt very much that the manual vs. automatic chlorine injection has anything to do with it unless dcfrey is secretly adding base to your pool water / chlorine mixture . Seriously, I think the best thing to do is to significantly lower your TA since we know that will help a lot with the total amount of acid, though may not help as much with the quantity of pH rise. So, first lower your TA a lot -- to at least 70 via Ben's Lowering Your Alkalinity process and see if you notice an improvement. If you do, you could lower it even more down to 50. You should also try and target a higher pH such as 7.7 and see how long it takes to move up to 7.8-7.9. If you find the amount of acid per time reduced, but the rate of pH rise is still unacceptable, then you could add the 50 ppm Borates which should slow that rise down though won't change the amount of acid you need to add.

One step at a time -- try the lower TA first since it's not hard to do and is easy to change back if for some reason you felt you needed to.

Richard

[mariner09]

I've also been experiencing pH creep. Over the last week, it's been hovering up around 7.8 - 8.0. To try something, I bought a bottle of pH down at Wal-Mart. I added about 24oz and got it down to 7.6. A few days later it was back up. Just finished the bottle this morning, 3 lbs of pH down in less than a week???

My TA is around 160.

I guess my bigger question is, is it OK to keep the pH up around 7.8?

We have had some big storms last week and more wind this week than usual, nice cold front came through in the middle of the week.

Come to think of it, one of my jets is pointed towards the surface and I have seen bubbles, maybe I need to lube the O-ring on the pump and re-prime..

[Amir]

Richard,
I can not access the link to the charts. Did you move them?
Thanks
Amir

[chem geek]

mariner09,

Yes, you can keep your pH at 7.8. The only downsides are a slight possibility of being more drying or stinging on the eyes since it's further away from the 7.5 that is around the pH of tears, but even that pH varies by person so I think you'll be fine. The other thing is that chlorine is a little less effective at that pH, but not by as much as the "traditional" industry graphs say because CYA helps to buffer disinfecting chlorine concentration. It's only around 10% less effective, so just bump your FC target up a bit to compensate.

You can lower your TA to around 80 to see if that helps. Then use 7.7 or so as your pH target after you've lowered your TA and I think you'll find a huge drop in the amount of acid you need and some drop in the rate of pH rise.

Amir,

No, I didn't move any of the charts and the link works for me right now and I don't have it protected in any way (i.e. it's visible throughout the world). Do you get an error message like it's a broken link? Does anyone else see that problem? Here are some links to various charts and graphs:

Free Chlorine Chart
Disinfecting Chlorine Chart
Outgassing CO2 Chart
Rate of pH Rise Chart
Chlorine Half-Life Graph (will be changed in future)
Disinfecting Chlorine Graph

Richard