TA/ PH battle

[Rabbit]

Ok, so having figured out so much about my pool thanks to this forum, I decided to see if my spa was ok. I normally just drain the water in the thing any time I feel it's becoming a problem. My normal routine from that point would be to just toss a bunch of bromine tabs in the filter bromine holder and let it run. A couple days later it would be just fine. Well I've always noticed the TA drops and drops over a few weeks time, so I've just been adding Leslie's "Alkalinity Up" (baking soda) to increase the TA. In the past the TA would go up and using dip strips I would check things and everything seamed fine. Well I don't test with dip strips anymore as I've gone to all Taylor tests and I'm having some major problems. My Ph was sky high today so I added some muriatic acid (very little) to bring it down to 6.8, I realized this would also decrease the TA. So I let the spa run for a while with both motors on full and the Ph went up to about 7.6 and I thought great. I then tested the TA and it was 50. Ok..too low. So I added Alkalinity up to increase the TA...and it did....but my Ph went way above 8.2 again. I repeated that process over and over...no luck. So right now I'm trying to get the Ph to stabilize around 7.0 and then I'll try to increase the TA.

So the question I have...what should I have done...and in what order. Clearly I did the wrong thing.

 

[JasonLion]

You need to keep the TA fairly low in a spa or the PH will rise as soon as you turn on the jets. If you can keep the TA at 50 or 60, the PH should stabilize around 7.6 to 7.8. Raising the TA above that till raise the PH too much.

 

[Rabbit]

You need to keep the TA fairly low in a spa or the PH will rise as soon as you turn on the jets. If you can keep the TA at 50 or 60, the PH should stabilize around 7.6 to 7.8. Raising the TA above that till raise the PH too much.

Ahhh, thank you!

The TA from my tap water is 120. This explains all of my drama with my spa and why I've had to change the water almost monthly if I'm planing on using it. So the question is what are the drawbacks to having a TA of 50 in a fiberglass spa ?

 

[MikeInTN]

There shouldn't be any drawbacks to having your TA @ 50 in a fiberglas spa; it shouldn't harm a thing.

 

[Rabbit]

There shouldn't be any drawbacks to having your TA @ 50 in a fiberglas spa; it shouldn't harm a thing.

So from what I've read having a lower TA can cause the ph to swing a bit more? That being said I just need to watch out for any low swings? Will the aeration tend to always increase the ph instead of it falling lower ? Is there a TA for my spa that might be considered too low ?

Thanks,

Rabbit

 

[JasonLion]

I wouldn't let TA go below 50 (assuming CYA is around 20).

TA does two different things. Higher TA levels help stabilize PH against external changes. At the same time higher TA levels cause PH to rise any time there is aeration. In a spa, with extreme amounts of aeration, you need to fine a point where these two effects balance out, not too much PH swing and not too much PH rise from aeration. Keeping TA around 50-60 seems to work well.

 

[MikeInTN]

Yeah, what Jason said...

 

[Rabbit]

I wouldn't let TA go below 50 (assuming CYA is around 20).

TA does two different things. Higher TA levels help stabilize PH against external changes. At the same time higher TA levels cause PH to rise any time there is aeration. In a spa, with extreme amounts of aeration, you need to fine a point where these two effects balance out, not too much PH swing and not too much PH rise from aeration. Keeping TA around 50-60 seems to work well.

Thanks,

I tested the spa this morning and the Ph was ~7.9. I opted to try and drop that a bit with muriatic acid. This worked however my TA went to 30. So I said..ok fine. The tap water is 120 TA. I drained off about 75 gallons or so and replaced it with tap, ran the jets for about 10 minutes and checked the Ph. It was back to 8.2. TA checked showed 50. Added a tiny bit more acid to get the Ph down to 7.7 and TA showed 40. Bottom line is I can't seam to keep the Ph below 7.8 with the TA above 40. My spa has a ton of aeration. Two 2.5 HP motors and lots of jets. Not sure if the ozone plays a part in all this ?

 

[Guest]

You aid you are running bromine, right? Then why are you trying to lower the pH wien it's only 7.9 ? I would not worry about the pH until it climbs above 8.0 . One of the advantages of bromine is it's activity over a wide pH range. Also, bromine tablets are acidic (as is the non chlorine shock often used in bromine systems) so a TA of around 100 ppm is ususally a good starting place for a bromine spa. What are you shocking the spa with, btw? (and you are using sodium bromide on each refill, aren't you?)

 

[Rabbit]

You aid you are running bromine, right? Then why are you trying to lower the pH wien it's only 7.9 ? I would not worry about the pH until it climbs above 8.0 . One of the advantages of bromine is it's activity over a wide pH range. Also, bromine tablets are acidic (as is the non chlorine shock often used in bromine systems) so a TA of around 100 ppm is ususally a good starting place for a bromine spa. What are you shocking the spa with, btw? (and you are using sodium bromide on each refill, aren't you?)

I was trying to get the Ph down as I find it will rise on it's own very fast. At the moment I don't even use the spa as we can't keep the water temp below 106. Nothing like going from 110 deg outside temp in to a 106 deg spa. I've never shocked the spa, I've run sanitizer and such through it before water changes. I normally just refill and add bromine tabs and let the ozone and bromine do their thing. Within 24 hours the Bromine levels get pretty high. The water clarity has always been excellent. I drain it about every two - three months. My tap water is 120 TA, so the second I hit the jets the Ph rises like crazy. I don't like jumping in a hot tub where the Ph has gone off the scale of the test. If you have any suggestions where I can keep the TA higher and the Ph below 8.0 I'm all ears. As it stands now the Ph will hit 8.2 + in a mater of 15 minutes of jets or 24 hours of just the circulation pump (one motor on low). I've also noticed the dip strip tests show the Ph to be just fine where all the liquid Ph tests I have show it to be off the chart. They both agree on the alkalinity. Is it possible my tests are being skewed by the bromine or some other source ? I can drain the thing and start over without much hardship.

 

[Guest]

How high is your bromine when you are testing pH?
Even with ozone you need to shock the spa occasionally to destroy bromamines,
Also, are you testing for free bromine or total bromine? (which can be much higher than the free bromine.)

 

[Rabbit]

How high is your bromine when you are testing pH?
Even with ozone you need to shock the spa occasionally to destroy bromamines,
Also, are you testing for free bromine or total bromine? (which can be much higher than the free bromine.)

Using a normal Taylor DPD test the Free is reading 6 and the combined 10. So I guess that would make the total 16 ? Glad I don't use the spa in the summer

So the question is then could that be causing my Ph reading to go way up, if so this would explain why I'm fighting a loosing battle. I may just drain off half the water and try again. That should kick the bromine down. Can I shock with liquid chlorine ? I'm happy my pool is doing so well, guess I have a lot to learn about the spa.

 

[Rabbit]

Drained and refilled spa. TA 120 , Ph went from 7.2 to 8.2+ in 20 minutes of running jets. I'm back where I started.

 

[Rabbit]

Ok...got the Ph back to a stable 7.8. The TA ended up right where it was before @ 40 with 0.5 ppm bromine. The conclusion, if I want my Ph below 8.2 I need my TA around 40. Not sure why it's being such a pain..but just the way it's going. I'm sure the Ph will rise a bit over the next few days and I'm sure the TA will fall a bit...etc. I'm finding my pool to be way easier to maintain.

 

[chem geek]

You can certainly cut down the aeration by disabling the ozonator (not just the ozone part, but the air injection part) and reducing the aeration jets except for when you use the spa and even then only those jets that you want. That should make a substantial difference.

 

[Rabbit]

You can certainly cut down the aeration by disabling the ozonator (not just the ozone part, but the air injection part) and reducing the aeration jets except for when you use the spa and even then only those jets that you want. That should make a substantial difference.

Running a TA of 40 and a Ph of 7.8 everything is holding perfectly. Course that will change if I start using it again.

Thanks

 

[WaterBeast]

Read this thread: http://www.poolspaforum.com/forum/index ... opic=12645

I had the same problem, but had it somewhat more in control from reading and experimentation. I've been working hard at understanding and getting the pH/TA battle even more tightly in control.

I am currently at:

280 gal spa
CH 130 - as low as my tap water was at fill, I deliberately chose not increase it and want it low.
TA 90 - I've been as low as 50. I like the idea of a higher pH to resist pH swing, but it does exacerbate pH rise from.
pH 7.7 - I'm trying to get to 7.6 while maintaining a near-zero saturation index. I understand < 8.0 is probably OK, but want room to spare.
Borates 30ppm - Will probably increase to 50ppm
Calcium Sat Index - Currently near 0
Bromine 3.5ppm
Filter cycles: 1 hours twice/day - Reducing to minimum helped daily rise quite a bit
Ozonator on - Don't plan on turning it off

I'm pretty new to the borates, but seem to be maintaining with about 1 tsp dry acid/day. Testing with base demand seems to validate borate resistance to pH rise. I like the lesser resistance to pH drop, as this is my most commomn water treatment, and this of course reduces TA. Increasing TA increases pH and perpetuates the cycle.

I will probably increase borates to 50ppm. Current pH rise (again, very new info) is maybe 0.1/day.

WaterBeast