rising ph levels

[chem geek]

Jim (jereece),

There's an experiment you can try that will at least isolate whether the bulk of the pH rise is due to the chlorine (or chlorine chemistry). If you double the level of chlorine in your pool which will probably double your chlorine usage, then if the pH increase per day and the amount of acid you have to add to compensate both roughly double, then the source of the pH rise is either in the chlorine (the MSDS is wrong) or in the chlorine chemistry (there is a breakdown or outgassing of chlorine as a basic or neutral process rather than being acidic, so the net overall isn't as neutral as originally thought).

The only processes I know that increase pH from chlorine are 1) when the liquid chlorine or bleach is added to the pool, 2) if the chlorine outgasses from the pool (which is a VERY basic process, but unlikely to occur enough in your pool), 3) when chlorine combines with ammonia or organics to form chloramines and chlorinated organics. The processes that are acidic and exactly counteract the basic (1) and (3) are 1) breakdown of chlorine by light, 2) breakdown of chlorine into chlorites and chlorates by temperature, 3) breakpoint of chloramines or oxidation of chlorinated organics.

If your "double concentration" chlorine test doesn't double the rate of pH increase nor the amount of acid you have to add (which you'll have to do more frequently to keep pH in check -- probably twice a week instead of once a week), then the source of the extra base is elsewhere.

I'll completely understand if you're not willing to try this experiment. It'll cost you twice the chlorine and possibly twice the acid plus is more maintenance, but you'll only have to do this for a few weeks (maybe just one week, if the results are immediately obvious). By the way, the double concentration of chlorine (8 ppm vs. 4 ppm) is no where near being hazardous. It results in 0.18 ppm HOCl which would be the same as adding about 0.4 ppm of chlorine in your pool if it didn't have any CYA in it.

Richard

[jereece]

First I want to run some lab tests. I'll try to do this weekend, but no guarantees. I was a lab chemist and water treatment operator for about 10 years (20 years ago), so I have some experience working with chlorination. I have a few lab tests that I want to perform. I will post a summary when I get them done. Not sure if it will tell me anything or not, but something I want to try.

Thanks,
Jim

[chem geek]

First I want to run some lab tests.

Cool. I'm on vacation starting this Thursday and through next week so I look forward to your results upon my return (and am keeping fingers crossed that you find out something definitive).

[jereece]

Chem Geek - I posted the results and conclusions to my testing here. Please review and let me know what you think.

Thanks,
Jim