Pool Itch and PH Keeps rising

[CandyMoss]

Thanks Richard,
Yes, you're right about me investigating pseudomonas as mentioned in that thread. Since then, I have nearly drained and refilled all the water, and while the most of the water was drained I poured in 20ppm of chlorine in an attempt to not only shock but to completely bomb the water. I then refilled the remaining 2/3 of water. I bought a test kit for bacteria, including pseudomonas and just tested the water yesterday - it came up negative which is good news, but makes me have to investigate further as to the itching problem. I've shocked and brought the values back in line so many times I've lost count - according to the test I don't have any harmful bacteria in the water and and I don't know how it could've survived my many shock and awe raids on the water. I've become so obsessed with solving this that my next step is replacing my sand filter . The pool surface is old and ugly and needs to be replastered next year and the equipment is also old - maybe old chemicals or itch-causing stuff is lurking in the pipes or equipment...I don't know.

However, I haven't tried a bacterial soap and will do that next. Even if the test says I don't have bacteria in the water...if I try a bacterial soap and it works...well, then that would mean the test probably is wrong.

As for the PH, I do have an aerator, at least I think that's what it is. Basically a return that sprays water in the air over the pool. Isn't aeration done to lower the TA without affecting the PH?

Thanks!
Matz

[chem geek]

Aeration causes the carbon dioxide that is dissolved in the water (as carbonates) to go into the air and this causes the pH to rise with no change in TA. It is the addition of acid that lowers both pH and TA so the procedure for lowering TA combines these two effects by doing aeration and acid addition together.

Aeration --> pH goes Up
Acid --> pH goes Down, TA goes Down
--------------------------------------------
Aeration + Acid --> TA goes Down

So the net result of the above is for the TA to go down which is what you have been seeing over the longer term. In the short term between acid additions, you just see the pH go up.

If you want to continue to use your water feature, you are going to need to live with running at a higher pH level and lower TA level. Since you have high CH, having a lower TA isn't a problem though 70 is probably the right place to be (I wouldn't go below 60). You will have less of a pH rise at higher pH so just keeping the pH at around 7.6 or 7.7 should be easier and isn't a problem in any way. With CYA in the pool, the variation in disinfecting chlorine concentration vs. pH is small. At the lower TA level you are now at, you should find that you add less acid, though you still see a pH rise. If you live with a higher pH target, then you should not only see less quantity of acid, but shouldn't need to add it as frequently. At least you know that with your water feature you have a GREAT aeration device if you ever need to lower your TA! You might try, as an experiment, turning off that feature and seeing if your pH rise slows down significantly.

In your list of measurements you said that the CH reading is hard to determine and sometimes doesn't measure. Are you using the drop-test for CH in the Taylor K-2006 kit or something equivalent? If you find that the endpoint is "fading" so doesn't stay at one color, then you can add some titrant drops to your sample before adding the calcium buffer and indicator. Then just count those drops in your total.

Good luck with the itching investigation. If something works (like heavy cleaning or changing to new swimsuits or changing the sand filter), let us know.

Richard