Tap water

[DannyD]

Helen,

I've never seen anyone having problems using tap water in Europe and several French or Belgian reference books just mention "Water" for preparing developpers...

It's not the same in the USA and i'm just asking a question : Why ?

Maybe it's because a lot of French areas have a high quality mineral water ? (Perfect for preparing the Kodak D76)
Maybe your US reglementations about drinkable tap water involves some additives ?

I don't know, but I want to know.

Any information will be appreciated !

 

[Ed Bray]

I have been reading this thread with some interest as I am the Asset Manager of 7 Water Treatment Works within the South West of England. The chemicals used in the treatment from each varies from site to site dependant on the quality of the source water and occasionally on the time of year. Strangely, it is easier to treat dirtier Raw water than it is very clean Raw water.

There are two basic means of making water Potable (safe to drink) and they are pretty similar across the world (of course there are other methods of treatment too (such as membrane, reverse osmosis, ultra violet and ion exchange), regardless of the chemicals used, the RAW water coming into a works is initially dosed with a PH correctant, this can be Alkaline (lime, Custic Soda, Soda Ash) or Acid (Sulphuric usually) which is needed to change the Ph to a level where flocculation can take place when a suitable flocculant (Aluminium Sulphate, PolyAluminium Chloride, Ferrous Oxide and others) is added.

At the correct Ph the flocculant is able to form a floc (positively charged molecules), this Floc is designed to take out many of the impurities in water such as Turbidity & Colour (which are typically negatively charged) and particulates larger than 2 microns in size such as a Cryptosporidium Oocyst. The Floc is then either, settled by creating a blanket with the addition of a polymer which aids the floc particles into sticking together or scraped off the surface of the water as a scum by the means of dissolved air floatation, these processes are known as the clarification stage of the process.

The next stage of the process is the filtration process and the water is then passed though either a slow sand filter or a rapid gravity filter, this takes out any further particulates.

Up to this point the water has not been treated to remove any bacterial content and traditionally there are three ways to do this, they are to a) Superchlorinate (using chlorine gas, sodium hypochlorite with a further stage of Dechlorination (using Sulpher Dioxide or Sodium Bisulphite) to reduce the amount of disinfectant remaining, b) 'Break point' or 'marginal chlorination' where the water is treated with enough disinfectant to ensure that after an ECT (effective contact time) there will have been a 100% 'kill' with some disinfectant left to carry through the distribution network and c) Ozone, this is a very good treatment as ozone will immediately kill any organic matter it comes into contact with (if you see the blue gas, it will be the last thing you see), but it is a very volatile substance and has the disadvantage that it does not leave a residue to carry through the distribution network so still needs some other form of disinfectant to be added.

At this point the water would have been treated chemically and biologically to produce a neutral and wholesome tap water fit for consumption.

Now we come to the bits that effect us as photographers, the additives:

Depending on where you live in the world, some or all of these chemicals will be added to the water at the treatment works before it leaves:

There will be level of residual Chlorine which will continue disinfection whilst the water travels through the distribution network.

Ph correction, this is almost always an alkaline added to take the Ph up to a value of between 8 and 9, this will surprise many people but there is a good reason for this, it is less corrosive to the large network of pipes and fittings in the distribution network that brings the water to your taps.

Phosphoric Acid, if added, it is before the PH correction stage as dosing it afterwards would negate the correction previously added. This is added to the water to prevent 'plumbosolvency' lead (poisonous heavy metal) leaching from lead pipes in older distribution networks and private service pipes.

Flourine, can be added to the water in many countries to prevent tooth decay.

Additives that may be added during the path through distribution:

Chlorine dosing at service reservoirs (this can be to lift the level of the residual in long runs)

Calgon dosing. this was commonly used to prevent corrosion is systems that were prone to corrosion and in effect lined the pipes.


Previous to my working in the Water Industry I was in Health Physics within the local Nuclear Base. We were only allowed to use 'De-mineralised' water not distilled (2 completely different things) on or in any of the nuclear plant.

Personally I use distilled water for my developer and my wetting agent, everything else is diluted with tap water.

Hope this is of some use.

 

[Josh66]

Thanks for the detailed reply, Ed.

Since starting this thread, I have been using distilled water for everything but the wash. I have read that tap water (even if it's bad for developer) should be fine for fixer and stop bath though. Since both of those last a long time, and distilled water is cheap - I use it for them too.

I haven't tried going back to tap water to see if the issues I was having came back, and out water supply very well could have gone back to how it was before by now - but I'll keep using distilled water just to be safe. It costs about $0.80/Gallon here, so it's not a big deal.

edit
I should try tap water again, now that's it's warm again (just as an experiment - not planning on switching back to it). I have a feeling that the problems might have been from mixing hot and cold tap water. Like, there was something in my water heater leaching into the hot water (copper, sediment, something else?). (But then why wasn't that a problem before? ...Maybe it just took a while to build up to a 'dangerous' level...?)