Tap Water; Alkalinity; Reverse Osmosis Treatment

lensmagic · Jun 15, 2009

I live in an area where the water is alkaline. The tap water is treated by the city. What chemicals the city uses I do not know. Because alkalinity, or the degree of alkalinity, is so important to consistent development, I use "distilled water" from the big box store. I am wondering if the use of a reverse osmosis apparatus to treat the tap water would provide water with consistent alkalinity. In other words, if we assume the alkalinity of the tap water fluctuates, would treatment of that tap water by reverse osmosis provide water of uniform alkalinity?

Kirk Keyes · Jun 16, 2009

Call your city and ask them for a report of the city drinking water. I was just mailed one from the city I live in. It should tell you the hardness and perhaps the alkalinity of your cities water and we can take it from there.

snallan · Jun 16, 2009

Treating your tap water with reverse osmosis will provide uniform alkalinity. A membrane in good condition should remove all large ions from the water, the pH of the water then being due only to ionisation of the water itself at pH 7 (at standard temperature and pressure ).

Rick A · Jun 16, 2009

I use a two filter in line system -- first is for sediments, the second is activated charcoal for taste, but I use it to remove chlorine and other minor impurities. Both together remove Iron, but I'm not sure how much, but I haven't seen any signs of iron stains on any of my materials. I do use deionised water to mix developer and fixer. Washing film and prints in unfiltered water doesnt seem to present any problems- Adams and Weston, and their cronies, washed prints in streams. Use a wetting agent in the end, and you should be fine.
Rick

michaelbsc · Jun 16, 2009

ralnphot said:
I use a two filter in line system -- first is for sediments, the second is activated charcoal for taste, but I use it to remove chlorine and other minor impurities.

I have nasty municipal water. This is basically what I do too, except I also have a refrigerator icemaker filter just before my photo chemical area. I have two big filters, a spun fiber sediment filter first, then a charcoal filter second, which all the building water flows through. Mine are the GE Whole House models, but I don't think they're any better or worse than other brands - readily available at Home Depot in the US. I'm not sure about other places.

Then, the water pipe that goes over to my photo area passes through an inline refrigerator ice maker filter. I use this water for everything - developing, washing, mixing chemicals, and it works great. Change the filters about 90 days or so. The sediment filter has a clear plastic housing, and when I can begin to see the buildup I throw them them all out. The water tastes good, makes excellent coffee, and the quality of the pictures reflects the skill of the photographer instead of the scum in the water.

MB

RobertV · Jun 16, 2009

Treating tap water with R.O. will result in a neutral pH=7 water. Followed by an UV lamp also the organic materials are destructed.
Normally it shouldn't be necessary trying to make analytical lab water. The report from the local tap-water company should give you insight information about the tap water. In Europe you can have access on the internet for the lab analysis of the local tap water.
By boiling your tap water you get rid of the oxygen, chlorine and a lot of calcium salts. In critical situations you can use destilled or deminiralised water. Critical developers in metal ions can be Xtol and low contrast document developers.

RobertV · Jun 16, 2009

Therefore a water tank in a lab system stays always full and is recycled to the R.O. unit to prevent that HCO3 acifies the water. The tank has also a 0,1um filter (anti-bacteria).

Kirk Keyes · Jun 16, 2009

Alessandro Serrao said:
Basically no, 'cause atmospheric CO2 will dissolve in water and will yield HCO3 which acidifies the water...

Which quickly results in a pH of about 4.5 to 5. Keep in mind despite this pH, it was very little buffering capacity and it will readily change pH and not cause any interferences when used for mixing photographic solutions.

Which brings up my original point about calling your local water beaureau and asking them about hardness and alkalinity.

dancqu · Jun 17, 2009

Kirk Keyes said:
Which quickly results in a pH of about 4.5 to 5.

And the more quickly as atmospheric CO2 each day is increased. Dan

nworth · Jun 17, 2009

Some water companies put some lime in the water to solve certain problems, but it is unusual. Most alkalinity is from natural sources and just isn't removed. If the alkalinity is due to calcium, the reverse osmosis treatment will likely work; for other things, maybe not. If you already have the equipment, you can give it a try and see what happens. Otherwise, I would use one of the commonly available ion exchange units (e.g Brita, and several others.

Aurum · Jun 18, 2009

Kirk Keyes said:
Call your city and ask them for a report of the city drinking water. I was just mailed one from the city I live in. It should tell you the hardness and perhaps the alkalinity of your cities water and we can take it from there.

When I needed this information for setting a dishwasher, years ago, I just phoned up a rather nice lady at the water company who could give me the information in a choice of 5 or 6 types of unit. I remember frantically flipping through the manual to find one I recognised

Just give them your post code (or Zip code) and they'll be able to tell you more than you need to know right off the page

Tap Water; Alkalinity; Reverse Osmosis Treatment

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