Pool Itch and PH Keeps rising

[CandyMoss]

Hi all - I've had trouble with itching on the arms since last year, so this year I've decided to go as far as I need to in order to figure out what's going on.

There are 2 issues in this post, because I'm wondering if there could be a connection between any of the values and the itch.

FC: 3
CC: 0
CYA: 40
PH: 7.4
TA: 70
CH: 400 (Hard to get a read on - most of the time it doesn't give a value)

The PH keeps rising rapidly within 2-3 days. I add muriatic acid to bring it down to 7.2 - 7.4 range, and within 2-3 days it will have risen up to 7.8+ and I need to add muriatic acid again. The TA has been fine around 100 but of course it keeps dropping when I have to add acid so now it's down to 70 and I will have to add baking soda to bring that up...I see a vicicous circle developing here. I didn't have this problem last year, but that's probably due to my CYA being out of whack (110).

Wkat do I do?
Thanks
C

[chem geek]

You had reported in this thread how you are using BBB and had CYA too high in the past and may have had the bacteria, Pseudomonas aeruginosa, that causes "hot tub itch". This bacteria takes a lot of chlorine to kill. From what I have read, it would take 0.25 ppm FC with no CYA which is equivalent to an FC of 9.6 ppm with a 40 ppm CYA level. So I would suggest shocking with chlorine even higher to 20 ppm and holding that level for a full 24 hours. Then let the chlorine level drop before going back in to swim. Also, be sure and wash all of your swimsuits since this bacteria tends to get transferred from place to place via swimsuits. I'm not sure if there is an anti-bacterial soap you can use during the washing but if hot water is used it has to be very hot to be effective (120+ degrees) since the bacteria actually thrive in hot water of 99F and are able to grow in up to 108F. You might even consider replacing your swimsuits.

As for your pH issue, do you have any waterfalls or other aeration features in your pool? With a lower TA of 70 you normally would not be seeing a pH rise, especially not with BBB. SWG pools tend to see more of a pH rise due to the aeration from the hydrogen gas bubbles that are produced in the SWG.

Richard

[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

[CandyMoss]

Thanks for your suggestions - I'll try and keep the TA at this lower number and allow a little higher PH and see how it goes.

I should've said that I don't actually run the aerator, I thought you asked so that in case I had one I could use it to adjust something.

The only "aearation" I can think of possibly happening is that I have 2 of the water returns pointing up toward the surface which causes some bubbling/movement...

Yes, I'm using the Taylor kit and got the reading by applying the method you described. And yes again, I will definitely post back a follow up when I nail down the problem.

Thanks a bunch!