Reverse Osmosis v. Deionized Water

thefizz · Oct 1, 2018

I have used deionized water for mixing developers, tomers etc. for a few years but recently noticed I can get reverse osmosis water much cheaper. I understand it’s not quite as pure but still much better than tap water so I’m wondering if it would be suitable?

jim10219 · Oct 1, 2018

It's going to depend on the water they start out with. It's hard to say, because there's not really a standard of purity in the end product. Each are made differently and treat the water in different ways that excel at removing different contaminants. Here in the U.S., most tap water is filtered through a reverse osmosis system at the water treatment facility. So it basically is tap water for many of us, or perhaps slightly better because it doesn't have to run through a gauntlet of pipes before reaching our house. For photography chemicals, deionized would probably be better, as it removes more metals from the water (though not many bacteria or viruses). For really pure water, both steps are often used, as neither one does it all.

Also here in the states, we can buy distilled water fairly cheaply in gallon jugs at grocery stores. That's what I use. It's not 100% pure by any means, but it's a good, cheap solution that works for photographic purposes.

REAndy · Oct 1, 2018

I agree with the distilled water. I can get it for 97 cents a gallon in plastic "milk style plastic jugs". I use this for mixing chemicals and diluting developer. I save a half dozen or so of the jugs and keep them filled with filtered tap water for pre-washing/soaking film and paper. That way it is at room temperature. My darkroom stays at a nice 68-70°F year round so I don't have to mess with temperature compensation for b/w work.

Paul Howell · Oct 1, 2018

I live the desert southwest, our water is really hard, even so I use tap water for most paper and film developers, the only time I resort to distilled water is for high dilutions of Rodenal (sp?) and for final rinse with a wetting agent before drying.

Alan9940 · Oct 1, 2018

I live in the desert southwest, too, and I use distilled water for all developers and RO water for everything else, except washing which is completed with tap water.

DWThomas · Oct 1, 2018

I'm on a well with relatively hard water, so I mix all my chemistry with distilled water and use it for the final rinse with wetting agent. I use the well water for general washing.

I used to think my water had high iron content, as there were rust stains in toilet tanks and such, but several years back, the pump failed and its replacement included new pipe of a plastic material and the stains have vastly diminished. The old steel/iron pipe looked as though it had nearly reverted to iron ore!

slackercrurster · Oct 1, 2018

thefizz said:
I have used deionized water for mixing developers, tomers etc. for a few years but recently noticed I can get reverse osmosis water much cheaper. I understand it’s not quite as pure but still much better than tap water so I’m wondering if it would be suitable?

Can't comment on deionized water. Never used it.

I've tested many reverse osmosis waters. They are close to distilled quality. (A rough estimate is 80% to 90% as clean when it comes to visible dissolved solids.) Tap water is filthy. Many municipalities have a 'toilet to tap' water recycling program.

To see the water distillation test photos from around the country Google:

'Distilling water is a quick acid test you can do to find out what residue is in your water'

Don't get bottled 'drinking water' it is terrible and is only charcoal filtered water which does next to nil. Always get 'purified drinking water'- it is generally reverse osmosis.

An example of residue from distilling 1 gallon of tap water from RV park Chillicothe, OH ...

pentaxuser · Oct 1, 2018

thefizz, I take it that you are sure that your tap water in Trim is not good enough for film processing. I live on the western fringes of East Anglia and water here is pretty hard but is still fine for film. Just seems an unnecessary expense to use other than tap water unless you do have problems.

pentaxuser

thefizz · Oct 1, 2018

Thanks for the info everyone.

thefizz · Oct 1, 2018

pentaxuser said:
thefizz, I take it that you are sure that your tap water in Trim is not good enough for film processing. I live on the western fringes of East Anglia and water here is pretty hard but is still fine for film. Just seems an unnecessary expense to use other than tap water unless you do have problems.

pentaxuser

I do use tap water for developing film and paper but when I make developers or toners to keep long term, I use deionized water.

slackercrurster · Oct 1, 2018

Amazing what is in your water. It all looks good to the eye...until you distill it.

AgX · Oct 1, 2018

slackercrurster said:
Tap water is filthy. Many municipalities have a 'toilet to tap' water recycling program.

To see the water distillation test photos from around the country Google:

'Distilling water is a quick acid test you can do to find out what residue is in your water'

Don't get bottled 'drinking water' it is terrible and is only charcoal filtered water which does next to nil. Always get 'purified drinking water'- it is generally reverse osmosis.

An example of residue from distilling 1 gallon of tap water from RV park Chillicothe, OH ...

-) This is a worldwide forum. Tap water qualities vary. The OP is not even located in the USA.

-) Minerals in water is typical, thus getting a mineral residue after destilling is typical too.

pentaxuser · Oct 1, 2018

AgX is 100% correct about the varying quality of tap water in terms of such things as hardness or softness making it difficult to transfer what needs to happen in terms of its use from one area to another. Generally speaking while mineral content varies the quality of tap water is very high in the U.K. and I'd be surprised in the same high standards do not apply to the Republic of Ireland.

thefizz's answer to my post raises the question of whether there is any reason why water that is OK for film processing is not OK for making developers and toners. I "make" Xtol with my tap water quite successfully. OK I am not actually making Xtol but I am simply adding water to a mix of ingredients. When you add tap water to any list of ingredients, does it depend on the specific ingredients and the specific content of the tap water as to whether you run any risk?

pentaxuser

Photo Engineer · Oct 1, 2018

Water quality is a huge variable. Even the purification methods vary including Chlorination, Bromination and Ozonation all over the world. It even smells different! RO is basically the method used to wash emulsions, albeit from very very pure sources. Yes, you can rely on RO but DW is good enough. I use tap water with no problems though and this saves me a lot. I only use DW for emulsion making.

PE

mshchem · Oct 1, 2018

My water is hard. We have a water softener, it converts the calcium carbonate to sodium carbonate. Terrible for my XTOL. I have a RO system, this is what I use for developers and final rinse, color chemistry etc.
One thing to consider is RO systems waste a lot of water. It depends on how hard your water is. You may use 5 gallons of water to make 1 gallon of RO. RO systems are banned in some areas due to water scarcity.

The city I grew up in had tap water like NYC, absolutely no need to purify for normal darkroom work.

DI cartridges are expensive . I've used RO, then a mixed bed (cation/anion) deionizing cartridge, followed by a carbon block filter. This was back in the old days when I was a analytical chemist (glorified lab technician ) we got 10 million ohm/cm water.

I plumbed in my RO, generic system, doesn't cost much to keep running.

If I had good tap water I would tap for everything.

Ko.Fe. · Oct 1, 2018

I moved from one 10 million people city in Eurasia to another fourth largest city in NA. It is officially safe to drink tap water in both cities.
I'm using nothing but tap water to mix my chemicals. BW, E6, C-42, ECN2. I forgot on which Kodak powder instruction for common BW chemical it is saying - tap water.
But in some other large cities I have been tap water was really soft. Don't know if then it has to be special water for chemicals.

GRHazelton · Oct 2, 2018

I use distilled water to mix the chemicals and to dilute the developer. Wash is with our tap water, which is very nice to drink. I mix PhotoFlo using distilled water. Back in the day I used tap water for everything, including processing Ektachrome. I do recall a sobering incident: I prepared to do some BW printing, mixed the Dektol with tap water in the usual way...and NO IMAGE! On a hunch I called the water department - this was long before email - and was told that in my area the pipes were being flushed, with sulphuric acid! Not strong enough to be harmful to drink, but enough to make a good stop bath! I was really glad I wasn't souping film!

thefizz · Oct 2, 2018

Thanks for all the replies, I should have been clearer from the beginning to say it was for long term storage of developers and toners mixed from raw chemicals, rather than one shot use.

mpirie · Oct 4, 2018

pentaxuser said:
my post raises the question of whether there is any reason why water that is OK for film processing is not OK for making developers and toners.

pentaxuser

Maybe the short-life of the film dev means that any bacteria or organic material has no impact, whereas the water used in making concentrated developers or toners that could last for years has to be as pure as possible?

Mike

pentaxuser · Oct 4, 2018

mpirie said:
Maybe the short-life of the film dev means that any bacteria or organic material has no impact, whereas the water used in making concentrated developers or toners that could last for years has to be as pure as possible?

Mike

That could well be the case. Maybe it needs knowledge of what chemicals are susceptible and a check on whether they are used in the toners, mixes etc that the fizz needs. I can say that Xtol is fine for at least 18 months mixed in very hard i.e.limescale producing water but this may not include the susceptible ingredients

pentaxuser

Ian Grant · Oct 4, 2018

I use deionised water to mix my chemistry (from raw chemicals) and my Pyrocat HD part A lasts about 4 years with no Glycol, with no deterioration. For actual use I just use tap water and I'm in a high lime scale area, no issues, but final rinse is deionised water.

Ian

Reverse Osmosis v. Deionized Water

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