Low TA perfect PH in Spa

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J

JetChick

0
Dec 23, 2010
2
Hi Folks,
New to this forum, but have used this site for the BBB way for our spa other than I use Bromine :) not bleach. Ok here is the question:
TA is at 40 which is low, pH is at 7.2, Bromine is at 15ppm, which are in the perfect range.
So, how do I raise TA without changing pH? Or should I not worry about it?
We have the iSpa 230 gallon (JUST LOVE IT)!
 
Welcome to TFP! :wave:

Are you using bromine tabs in a floating feeder? If so, bromine tabs are acidic and given your lower pH you'll want the TA to be higher to compensate. You could raise the TA to 60 to see how that goes and if the pH still tends to drop over time then raise the TA to 80, etc. Basically, you want to find a TA level where your pH tends to be stable over time. Note that the TA will slowly drop over time due to the acidic bromine tabs.

You can use The Pool Calculator to calculate dosages. Add the baking soda very slowly to the water with the circulation pump on, but not the jets. That will minimize how much the pH rises. It's OK for the pH to be in the 7.7 to 7.8 range, especially with bromine, though if it settles in at 7.5 then that's fine as well.
 
I put Bromine tabs in the return basket. Bromine level was typed in wrong it should have been 10 ppm not 15.
So how do I raise the TA and not the pH? If I use baking soda that will bring both the TA and pH up
Spa temp is 101 degree's.
 
Baking soda won't raise the pH very much if you add it slowly without having it outgas carbon dioxide. For example, going from 40 ppm TA to 80 ppm TA would take about 1-2/3 ounces volume (10 teaspoons) volume of baking soda and with no outgassing would raise the pH from 7.2 to 7.42. With outgassing, the pH could go higher. If it goes up too high for you, then just add a small amount of dry acid. Say, for example, that the pH went up to 7.7 instead; then you could add 1/2 teaspoon of dry acid to lower the pH to 7.5 and the TA would only drop by about 1 ppm.
 
So I have just done a fresh refill of my 330 gallon spa. I use well water so the PH and TA are normally quite high. I adjusted TA to around 120 and then kept adjusting PH until it was 7.2. I then tested TA again and it was 10! Adding 0.5oz of soda ash raised the PH to 7.8 but TA is still 10 - can this be right? Should I add 5.6 oz by volume of soda ash as suggested by the pool calculator?
 
Alk gets eaten before the pH will drop. What I don't understand is why do you want the pH so low? 7.4 to 7.8 is fine for a spa. The bromine tabs are going to pull the alk down as they erode and then start on the pH.

chem geek has forgotten more than I will ever learn when it comes to pool and spa chems.

Scott
 
To lower the TA from 120 ppm to 10 ppm in 330 gallons would take 12-1/2 ounces weight (8.3 ounces volume) of dry acid which is a lot. If that's what you added then your measurement is correct. As was pointed out, you don't want a final pH target of 7.2. If you were doing the TA lowering procedure, you don't stop when the pH stays at 7.2, but rather when you get to your TA target. Aeration will have the pH rise, even if the TA is somewhat low, though it takes longer.
 
I mis-spoke slightly - I was trying to get the PH in ~7.5 range. With my well water high PH is normally my problem and I find it a bit hard to tell the difference between the PH values in the range of 7.8 - 8.2 using the Taylor K-1000 - the redish/purples are hard to tell the difference. What I saw was the PH staying above 7.8 as I adjusted - and then suddenly dropping to around 7.2 - that is when I tested TA again.

I am adding Baking Soda to try to get the TA back up again. So should I focus first on getting TA correct (and what is correct for a spa?) and then seeing what PH stabilizes to?

Edit I now have TA 50-60 PH ~8.2
 
The TA level you should have depends on the type of sanitizer you plan to use. If you plan to use the Dichlor-then-bleach method, then you want a low TA -- about 50 ppm. Your pH target would be around 7.7 or 7.8 unless it happens to settle in lower. Note that aeration tends to make the pH rise, especially when the TA is higher. If you plan on using Dichlor-only or bromine, then a higher TA probably around 70 or 80 would probably be more appropriate. However, at this point, why don't you leave the TA low if the pH seems to want to rise. It's easy to increase TA, but harder to lower it.
 

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Well, that's quite strange. From past posts, I am assuming you are using the TF100 test kit, correct? Is the bromine level high? I'm thinking that if it's high, that it's throwing off your pH reading. Chlorine levels above 10 ppm, so bromine levels above 22.5 ppm, will often falsely show up as purple in the pH test making you think the pH is higher than it really is. Even chlorine levels above 5 ppm, so bromine above 11.2 ppm, can start to influence the pH test when the TA is lower.

Do you have lots of aeration and is this spa uncovered? If you turn off jets and cover the spa, the rise in pH should slow down. You can add some dry acid to lower the pH -- just not very much. It won't lower the TA by that much. Add just 2 teaspoons of dry acid with the circulation pump running (not the jets). That should bring the pH down from 8.2 to around 7.4-7.5 while only lowering the TA by about 4 ppm.
 
Well the bromine is a bit high at about 15 (= 6.5 for chlorine on the TF100 drop test). Not sure why it is high - it a fresh refill 4 days ago. I followed the 3 step system (added sodium bromide to give 30 ppm per manufacturers instructions, shocked with MPS and then used a floater set to 5 ppm).

Not sure what to do next.
 
Try adding 2 teaspoons of dry acid, let it mix for around 10 minutes, then measure the pH. If you are using bromine tabs and MPS to shock, these are both acidic so should keep the pH down, though will also lower the TA over time so you'll need to increase it over time, but keep the TA low if the pH still tends to rise. You can turn down your bromine tab feeder since you seem to have plenty of bromine.
 
OK I added the 2 teaspoons of dry acid last night.

Today the readings are PH 7.8 (I think - it is hard to tell the purple/reds but it is certainly not lower than 7.8), TA 50 Br 10 - so getting better I guess.

I have set the Br floater to around 2ppm two days ago - I'll watch the Br level to see how it moves. We haven't used the hot tub much in the last couple of days.

I assume I should leave the TA and PH as they are for now.

One final question - I have some 'Control the pH' from Spa Choice (http://www.spadepot.com/shop/Control-th ... 4C634.aspx). It says its active ingredient is phosphate buffer (as KH2PO4/K2HPO4). Anyone know anything about this product. Would it be appropriate to use in my situation to try to stabilize the PH?
 
One week after monitoring PH and BR each - but adding nothing to the SPA (except the Bromine floater set at ~2-3pmm) - TA 40, PH 7.8(maybe even a little higher) and BR 6-7ppm. The SPA was lightly used most days of the week.

So the PH is staying high TA dropping slightly and BR seems to OK. What should I do - just leave it as is?

Edit - should I consider adding boric acid to control the PH?
 
Well, at least the pH doesn't seem to be rising much above 7.8 even after a week of light use. That is some hope. Adding 50 ppm Borates (say, from boric acid such as Proteam Gentle Spa) will help to buffer the water, but while the pH won't rise as quickly it will still take about as much acid to lower it as you are using now. So at least it can lessen the frequency of acid addition, if not the total amount. I'd just target a somewhat higher pH of 7.7 rather than always trying to get it to 7.5 or lower. With the low TA (and CH) there is no risk of scaling at the higher pH. Bromine is still very effective at that pH.
 
Hi everyone,

I cannot figure out how to start a new post, so will piggyback onto this one. I have started up an older spa (1998) for first time in a few years. I am having problems with TA & PH. If TA is good, PHis through the roof. If ph is good, TA is 50. I am using dichlor shock, and household bleach until a nature 2 cartridge arrives at which time I will use dichlor shock and MPS. Is it going to be ok to leave TA at 50? Thanks for any input.

Bev

TA - 50
PH - 7.6
CH - 200
Temp - 100
FC - 3.0
Water - clear
 
Go to the "Spas and Hot Tubs" category and click on "New Topic" to start a new thread.

Keeping the TA at 50 is fine if that is where it needs to be to keep the pH stable.
 

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