Adjusting water ph

[adan]

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This is just a funky little chemistry problem.

In order to reduce acidic leaching of lead from old plumbing, the Denver Water service adjusts its tap water to a pH of 8.8 (increased very recently from pH 7.8). That is to say, rather on the alkali side of neutral (pH 7).

I suspect this is why I have problems with occasional overdevelopment (which do seem to have increased since the water change), since development activity increases with alkalinity.

Does anyone know a simple formula for reducing water pH from 8.8 to ~7, such as "add XXml of grocery-store cider vinegar (5% acetic acid) to every 500 ml of solution?" A couple of drops of lemon juice? Rice vinegar? Other ideas?

I'm sure some will suggest using distilled water - but I don't see that distilled water has a guaranteed pH either, plus it is expensive ($24.00/gal-4 liters, locally - technical grade), and if shipped, has a carbon footprint.

https://www.chemicals.co.uk/blog/ph-of-distilled-water

So on the whole I would much prefer to simply knock the pH down a couple of notches with kitchen chemistry applied to the cheap temperature-adjustable tap water, if possible. I'm not too picky - I can accept anything in the range of pH 6.5-7.5, I expect.

Of note, Covid lockdowns make it a bit tricky to get hold of litmus or pH testing materials right now, locally.

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[jaapv]

Swimming pool suppliers sell pH- powder. And testing strips.

[giannis]

Stop bath solution is cheap too and gives a colour indication if the ph has risen. This is for washing after development right, or also mixing chemicals? If mixing chemicals, you can get just bottled water (and check the ph on the label), much cheaper than distilled.

[sblitz]

Add lemon juice .... exactly how much, not really sure. You should be able to get Ph strips in the mail from a pool service firm, I am sure there are plenty in the Denver area as well as on line. Then experiment. Water is free and the lemon juice won't cost much either.

Makes me want to check on NYC water PH.

 

[sblitz]

That is high, NYC is 7.2 and I know it is soft water too .... 

[fatihayoglu]

I'd use de ionized water to deal with this issue

[Bobitybob]

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If you have any, you could try adding captured rain water which is supposed to have a ph of between 5 and 7, and it's free and soft.

[LocalHero1953]

pH 8.8 is surprisingly high, but within international standards (but I think US EPA sets an upper limit at 8.5). Water companies normally keep it the alkaline side of 7 (7-8) to minimise the risk of dissolving lead from old pipes. Also the built up scale in pipes masks corrosion leaks; if the scale is dissolved by low pH water then the plumbing system leaks.

There is no quick answer to this, Andy. As you probably know pH is determined by the quantity of H+ ions, which in turn is determined by the balance of dissolved constituents, including CO2 which comes from the air; the nature and quantity of those constituents affect how much lemon juice, citric acid, vinegar, battery acid etc you should add to achieve the desired pH. The word is 'buffering': a well-buffered solution takes a lot more acid to change pH than a poorly-buffered solution. If you know the makeup of your water then you can calculate the amount of an acid you need to add. In practice, it is far easier to do it by trial and error; water companies do the same.

(Water quality used to be one of the bits of my job. At times it was ALL my job, including occasionally in court.)

Edited June 1, 2020 by LocalHero1953

[adan]

Thanks, Local. Yeah, I thought about the buffering in the developer (borax, in D-76). And maybe that means I just shouldn't be too worried about the problem anyway. I notice that in announcing the pH change, Denver Water did give some advice to our brewers and distillers (of which Colorado has many) - "YOU figure it out!"

https://www.denverwater.org/your-water/water-quality/brewing-beer-home

To answer giannis, I was intending acidifying (or dealkalizing) only water used for mixing developer, which is the most critical chemical for image charateristics. Not worried about wash or the other chemical steps, which don't require the same precision.

In the absence of any better testing regimen right now, I did run a non-critical roll last night in D-76 stock, with 1 ml of rice vinegar (listed as 4.5% acetic acid) added.

1) it did no harm.

2) it did not seem to have much effect, except that I used Kodak's "book" time, and the result (contrast and shadow density) looked about the same as when I pull development time 7% with untreated water.

I guess my main objection to bottled water of any kind is that somebody is burning a fair amount of fossil fuel to move it around, at 997kg per m^3. Water is heavy. Whereas Denver's piped city water is being delivered 1) locally, and 2) via gravity (all those mountains and snow melt) or with electric pumps (Colorado is producing 29% of its electricity with renewables).

[giannis]

17 hours ago, adan said:

To answer giannis, I was intending acidifying (or dealkalizing) only water used for mixing developer

Ah fair enough, this makes sense. So does buffering your developer. Though most general purpose developers (D-76, XTol) are well buffered, especially XTol if I remember correctly.

You idea is sound, get some PH strips (or a cheap PH meter, you should be able to find one for ~$30), and then experiment with how much vinegar you need to put in. Note down the quantities (both vinegar and water) that were required to bring it back to neutral, and use this recipe in the future.

[Doug A]

Shop around for distilled water, in the US at least. I just paid $1.19 for a gallon of distilled water at the Acme (Albertson) supermarket. Just be careful that the fine print on the bottle doesn't say that the water is "suitable for use in applications that require distilled water." It has to say "steam distilled." Using a 250ml stainless tank and the Ilford Method of film washing I use less that 1.5 liters of water to develop a roll of 35mm film. That works out to about 45¢ per roll.