Darkroom H2O Filtration/Treatment

[Pupfish]

For some years now, I've been buying purified bottled water to do all my E6 and C41 mixing and washing, which adds about $4 to the cost of a typical Jobo run. (I do this because my tap water is supplied by a cistern constructed out of concrete, and a rusty steel tank. Half the year I live on rainwater, and half the year have it trucked in to my ridgetop home). I also buy a lot of purified H2O this for my coffee and drinking water supply, and I'm tiring of all the cost & transportation, not to mention the number of plastic jugs that need recycled.

My needs probably won't exceed 21 gallons a week, all up.

What are some reasonably-priced (>$500) options others have used for purifying their darkroom water supply e.g. small scale reverse osmosis or distillers. (Anybody got a solar still design to recommend? I've got plenty of sunshine and real estate to work with). What are the potential pitfalls of each (pH changes, etc.) as relates to film processing? Thanks!

 

[bobwysiwyg]

Came across this..?

http://www.epsea.org/stills.html

 

[Mike Wilde]

small r/o unit here

Mine came from a find put out at the curb on a community recycling day. New osmosis element for $140, and prefilter and carbon polisher chamnged annually for about $30. The osmosis cartridge is approaching 4 years old, and no sign of throughput going down.

I am r/o'ing town processed water. We use it for coffee, ice cubes, making up dehyrated milk powder (milk seems to last longer before going off by doing this) and of course, film developers and final rinses.

Because I start with town water, pH is good - always close to 7.

If I was on a gravity system, I would need a pressure booster pump which would run frequently to mash the water though the R/O element.

 

[lonepeak]

Okay, here's my 2 cents...you can pick up a good RO system on that auction site for cheap. A small boost pump on the feed line will deliver the pressure needed to force the water through the membrane in case your gravity feed does not generate 60 PSI. One thing to consider with that is to get one that takes standard filters that can be purchased at the local store. Some units use proprietary filters that drive up the maintenance costs. The purification membrane and polishing filters are made by a small number of companies and can be purchased online when they need replacement. A good TDS tester is a must in order to insure your system is actually purifying the water. Once the water is purified, it can't go into any lines that are metal or have fittings that are metal so you'll need to use PEX or a similar product to plumb to your fixture. It corrodes the metal and changes the TDS/PH of the water. I use a small unit coupled to several 3 gallon tanks and it generates all the water I need. You can also use a well tank it if you need more but the bigger tanks cost a lot of money. I hope that helps.

 

[Kirk Keyes]

Call your Culligan man and see what he wants for it. If you are actually going to be drinking it, I'd get something easy to use and commercial quality.

 

[Pupfish]

Thanks, guys.
Love the link to the DIY solar still... cheap and easy would be ideal if I can figure how to keep it from freezing up in winter.

My facility isn't just gravity fed, I can boost the pressure on the electric pump to 60psi if needed. I'm off grid but have a PV array, wind turbine backup LPG generators and a constant 120VAC.

Do most R/O units have a bypass or waste 3 gallons per gallon of filtered pure water? My water supply is limited to what storage I've got or what's remaining, and this gets to be a problem sometimes, moreso if I've got an R/O unit running full-time that wastes water. Costco advertises one for under $300 that recycles water into the hot water line (which would be somewhat less-than-useful on the line to my temperature control valve in the D/R sink):
Dead Link Removed

What's up with the pH post-filtration that it corrodes pipes? Would this also true of distilled water? I've been using distilled and R/O purified water for developing film for a long while, without issue-- so maybe it doesn't matter to E6 chemistry?

 

[lonepeak]

I worked in the commercial purification business, grocery stores etc, for over 10 years. My experience is mainly with units that produce 1 to 2 gallons a minute. The short answer is that for every gallon of purified water you get there's a gallon that is the waste. There's the crystal clear gallon and the milky white gallon if you're in a hard water area like the southwest. I'm not sure you'd want to reintroduce that into your hot water system. I'm also not sure what occurs chemically with the water and metal (stainless is not affected) but once you separate the water from everything else, it wants to pull it back into the water. After a year or two leaks start to develop in the metal. You'll notice in the installation manual that there's no metal tubing or fittings until it reached the faucet. Those are easier to replace. Distilled would do the same if it was in a metal plumbing system but usually that's bottled. The Costco unit looks good except for the fact they almost admit that they have a lot of water for the drain. Maybe you could contact Watts directly and confirm the amount of waste??? These systems only run went the tank pressure drops and once the pressure is up, they stop so there's no waste occurring. That's what makes them a plus over the old distillers. Hope that helps.

 

[Claire Senft]

Do you have a dehumidifier?

 

[Pupfish]

No, being that I'm in the hills of Central California at 5000 feet where high humidity is rarely the problem in summer, I have a humidifier going much of time in my D/R as the RH is more often paper-curlingly low, rather than high. Single digit RHs are not unheard of from June through October.

With the 1:1 or greater waste, RO units would work better in the half of the year when I have plenty of rainwater (usually November-May, but it's been late this year). A solar still is probably the best answer in summer and fall, when my storage-only supply is tight.

 

[nsurit]

How about an extra fiberglass tank to collect and store your photo use rainwater. Bill Barber