just wondering as pH tends to not move once TA is lowered to around 70-80 in most pools I've come across but I've seen TA of 50 in one pool and pH climbs. I think I read somewhere that TA is a buffer and we would require still a certain amount. Is this correct? would raising the TA up a little using baking soda help lock in pH?

Thanks.

Raising the TA with baking soda will only make the pH climb faster. If anything, you might need to lower the TA.

Even at a TA of 50 ppm, the pH can still climb from the outgassing of carbon dioxide. If the water is heated and/or aerated, the outgassing will be increased.

If the pool has a salt water chlorine generator, then the pH can rise from that. If the pool uses sodium hypochlorite, then the pH can climb if the sodium hypochlorite has excess sodium hydroxide. If the pool has been plastered in the last 30 days, then that could contribute to pH rise. If the plaster is over 30 days, then a low CSI can contribute to pH rise. If the pool has scale and a low CSI, then that can contribute to pH rise.

Increasing the pH to 7.8 can help reduce the amount of carbon dioxide. Increasing the Cyanuric Acid level will provide some pH buffering and will allow you to use less cell time and/or sodium hypochlorite.

Adding borates to 50 ppm will help buffer the ph from rising as fast.

Also, if the TA is not rising as the pH does, then the pH rise is due to the outgassing of carbon dioxide. If the TA is rising as the pH does, then the pH rise is due to the introduction of some sort of base. What is the target pH, how fast does it rise and what is the TA doing?

What further details can you tell us about the pool? Indoor/Outdoor, all chemical levels, SWG, concrete, vinyl, fiberglass etc?

Thanks James. I think I will add borates. Its a gunite pool with swg.

I think raising the cya would be a solution. I believe this could be the main reason the pH is raising and rising faster than it should. I don't mind a little rise but not shooting up to 8.0 in 1 week. cya was 50ppm I raised it to 80ppm so this should hopefully help.

Thanks again!

we run swg's and some have heaters. I've always wondered if I'd ever have to add baking soda to raise TA. as we are talking swg pools I never have to use borax to raise pH as it usually rises on it's own. I have to use more acid than with tablet run pools. I find I am able to drop TA really fast and sometimes the pH stabilizes and I don't need to add anymore acid. on other pools pH just needs a little adjustment on a weekly basis. this if fine with me. but like you say there are other factors to consider and this could be why the pH shoots up high.

I'm offering the borate service, increasing CYA to 80 and dropping pH down to 7.2 to get the TA lower.

I think that I would try the borates and cyanuric acid first before lowering the TA. 50 ppm is already pretty low and you should be able to manage at 50 ppm. I think that I would keep the pH at about 7.8.

What is the calcium level?

Is the TA rising with the pH, or is it staying the same as the pH rises?

Thanks. Some info on this pool:

gallons: 14,000
FC: 7.5
CC: 0
pH: dropped to 7.4 Added 50 oz of acid (2 full scoops that some with CalHypo bucked)
TA: 70 (3 weeks ago TA was 50 with CYA of 50, Then TA was 60 with CYA of 80 now TA this week is 70 with CYA of 80. maybe my tests were a little off?)
CH: 360
CYA: 80
Salt: 3,500
Temp: 80
SWG: 35%
Filter: 10 psi

Those numbers look pretty good. Just keep the CSI about -0.1 to -0.2 and you should be fine. With those numbers and a pH of 7.8, your CSI is -0.13, which is very good. I would avoid using calcium hypochlorite.

Thanks James. Yes pH was up around 7.9-8.0 on Friday so I dropped it down to lower TA but it probably bounced back up by now. I don't carry tablets, CalHypo (used to and got some scoops left over I use to add acid), or anything harsh like that. Only carry acid to lower pH, some baking soda, borax and some backup DE powder if the owners run out. But they keep DE, Salt and CYA in pump room for me to use when necessary. Works out nicely.

I like -0.1 to -0.2 seems to keep the cells (once pH is stable) clean.

50 ppm Borates will also help keep the cells clean as they prevent the pH from rising as much near the hydrogen gas generation plate -- they roughly cut the amount of this pH rise in half.

only prob is its expensive and I can only offer them this service.