TA

[bof]

Help

My pool is 19500 gals
FC 5.8
Temp 20 C
Ph 7.7
CYA 75
TA 0

Is this right it was at 25 2 weeks ago. Can the ta be at zero, I have tested this twice and got the same result. Can anyone help me with the this. All advice welcome.

 

[Patrick_B]

Hey Bof,

Just covering the simple stuff here, did you add acid since the last test?

Are your sure the pH is correct? Usually, a higher TA would be expected at a 7.7 pH.

Did the test turn red immediately when you first started to titrate with the final reagent?

 

[Richard320]

It's hard to give advice to you, since I know the preferred test kits and chemicals are not readily available cheaply in Europe.

If you've been chlorinating with dichlor or trichlor powdered chlorine, then it's very possible your TA has dropped that low. They are both acidic. You should have added baking soda when TA was at 25 - that's way too low. Your surface may be tile, but the grout can still be weakened by etching, so you should consider it a plaster pool. .

 

[JamesW]

It's not possible to have a TA of zero with a pH of 7.7 and a cya of 75.. The test titrates down to a pH of 4.5 to get to zero TA. Your tests are probably not accurate. How are you testing?

It's theoretically possible to have a very low TA and a pH of 7.7. For example, distilled water with a little hydroxide to raise the ph. In that case, there is no alkalinity to buffer the ph change, but the hydroxide would measure as TA in the titration test.

In your case, your cya of 75 would contribute about 25 ppm TA at a pH of 7.7.

Also note that whatever brought down the TA would have brought down the pH. Even if you had a lot of aeration, the pH would not go up. In fact, once you pass the equilibrium point with CO2, aeration will lower the pH.

Have you ever used bromine or bromide salt?

Have you ever used a hydroxide base, like sodium hydroxide, to raise the pH?

 

[bof]

Hi all
Sorry about my delay in replying I am using a Scuba 2 digital tester. I have found that occasionally my results are way off, but I do not know why. I have checked my results with a friend who has a great test kit, and the results are similar. I have decided that when the results are way off to clean everything go have a cup of tea and start again.
Tests today
Temp 22 c
Fc 3.4
pH 7.9
TA 116
Cya 76

I am now going to add chemicals. Thanks for your help.

 

[jblizzle]

And this is why we do not like to trust digital testers.

 

[Patrick_B]

Indeed, digital testing equipment that is reliable is far too expensive to be practical for the average pool owner, and quite unwarranted. Simple titrations are more than adequate, and very dependable.