PH and TA bouncing

[miwitte]

Been doing BBB for almost 2 years and things have been really smooth, however this year I am having some issues with PH and TA. I run a Stenner for injection that's works like a charm 30 minutes raises FC by 1 PPm so its really easy. My PH and TA were great last year, my PH never really bounced around and my TA was sitting at 80 a little low but folks said to leave it if no issues. I've only been in pool for about 3 weeks its not been nice here so really haven't been looking at numbers too closely except for FC. Pool is perfectly clear so no issues. I did notice some metal staining this year(I have a heater) and was able to remove them with vitamin C tabs in a sock rubbing them but it also killed my chlorine so I had to be careful but no issues from that. What I have noticed is that last week my FC was a little high around 9 my PH was 8 my TA was 100. I let the FC come down to 5 and my PH is 7.8 however my TA is now 80. I know that adding bleach will raise PH some so I expected to possibly see the PH come down but not the TA. I even bought new chemicals off Amazon last week as I was wondering about that.

So my numbers
FC 5
CC 0
CYA 60
TA 80
PH 7.8
Cal 180

Also I was reading that my TA should be higher to prevent staining so what numbers for TA 110? Also I like to keep my PH at 7.6 so its still high to me. ALso can a higher FC reading like 9 affect the Taylor numbers for PH and TA? That was my initial thoughts as to why the numbers are skewed.

Just looking for a sanity check.

 

[JVTrain]

A few things. To prevent staining, it's recommended to keep pH on the low end, 7.2-7.5 or so. Sequestrants will also help. TA level won't have any effect on whether you get stains or not.

80 ppm TA is not low. It's fine to go as low as 50-60 ppm provided your pH is stable.

The pH (phenol red) test can be skewed high at FC ppms greater than 10. I'm not sure if that's a hard number, or if the pH may be slightly skewed upward at 9 ppm. Higher FCs and other interferences can make the TA and CH tests have different initial colors and endpoint colors. See notes for tests here: Pool School - Extended Test Kit Directions

Sometimes with new reagent bottles, the TA test can be inaccurate (high) due to static electricity on the tip of the bottle making the drop size smaller. Wipe the tip with a damp cloth before each drop when doing the TA test, especially with new reagents.

 

[miwitte]

so ive read in quite a few places where low TA will cause staining(it was 60-70 PPM all last year and PH was steady) I also do get some eye burn even with PH 7.6 and FC at levels recommended by CYA so I raised it to 100 a few weeks ago but now its back to 80PPm which I thought was hard to get TA to move like that. Which is why I suspect interaction with higher FC levels and PH and TA readings. As far as reagent, I actually tested it side by side with what I had left in kit and they are the same 7.8. Finally I thought I read here where the bleach will raise your PH. I typically need to inject 3 PPM to keep it constant, however with a large party and lots of sun I was injecting more and it floated up to 9PPM. Could this cause my PH to rise from 7.6 to 8.0? Then by injecting less this week its down to 5 would the PH then go down as well?

The results of a low TA may be one or more of the following:

• etching of the plaster, marbelite, marcite or tile grouting;
• corrosion of metal parts (pool heater, steps, scoop pole, . . .);
• staining of the pool's surfaces;
• green water;
• burning eyes and itchy skin;
• pH bounce (rapid fluctuations in pH).

 

[pooldv]

In my experience none of those is accurate except the last one. And what is the definition of low? My pool and pH perform best when my TA is 50. And none of those things has ever occurred. In fact, I find that when TA gets too high (110ish) my water becomes sticky feeling and more drying to my skin. My chlorine is normally between 8 and 12 and my CYA is 80. When my pH reaches 8.0 I lower it to 7.7 - 7.8 except when I am lowering TA and then I lower it to 7.2.

PH does become erratic in most pools with TA somewhere between 40 and 50.

 

[miwitte]

Ok so I am just going to leave things as is its been working for 2 years with zero issues no algae. I just saw a anomaly with the PH and TA with FC levels so was wondering what was going on. Also I do have a vinyl pool while you have a gunite so things may be a little different.

So now onto the next question and that's the staining. I was just in and It appears its a little worse than I thought, pretty much the whole pool has it. vitamin c tabs gets rid of it so what's the next course of action. I've seen some products most say need to be done at very low FC levels which I hate doing when pool is 85+.

 

[pooldv]

With a vinyl pool I'd go a bit higher on TA, 60-70.

The next step is an ascorbic acid treatment. Yes, FC needs to be low to 0. Yes, that is more scary when the water is 85. The process recommends adding polyquat60 algaecide to help prevent algae. And it doesn't take long to work and you can start raising you FC back to minimum after the stains are lifted.

More here about stains and a link to the AA treatment, Pool School - Pool Stains. Read through it and see what you think. If the stains are new and light then a sequestrant ight lift the stains and sequester the iron.