water for coolant - maybe I am overdoing it?
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  1. #1
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    Default water for coolant - maybe I am overdoing it?

    Summary - water qualty report required for new waterjet makes me wonder "Is the hassle of getting RO water from the grocery store to use in mixing coolant actually worthwhile???"

    The coolant in my shop does not stink. It works fine. I change it out very rarely (think years) though I don't run anywhere near as many hours as most of you do. This is all goodness so of course "what's the problem Bryan???"

    Since I got my first enclosed VMC and started using coolant, I've always used Hangsterfer's S-500CF, which I've always mixed with water from the grocery store pure water machine. (By hauling 8 or 12 or so 5-gallon carboys back and forth.) This is a hassle but always worked.

    These machines have a label that goes on at great length about how wonderful they are, but the gist is:
    charcoal, UV-light, some more filtering, RO, some more filtering, UV-light, etc.

    In other words, filters, UV, RO.

    Recently, I had the tap water tested as requested by a waterjet vendor, for a new waterjet that is coming. And as I read the report the water is VERY soft and has zilch wrong with it. (Though they don't test for bacteria.) Various public sources suggest the tap water is also very low in bacteria. (This is from the Seattle Metro water supply used by basically all of the city water supplies in West King County.)

    Soooo......

    Should I just mix the coolant with water from the tap? What are RO and UV treatment actually getting me? (I've not had the grocery store machine water tested, for all I know it's no better.)

    Thoughts? Experience? Any members in the Seattle area actually tried it?

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    I hauled 10 -15 gallons at a time of distilled water from the grocery store at roughly 86 cents a gallon for longer then I care to say. It always seemed like the wrong way to go but it worked, if you want to call it that. When I got another machine with around 90 gallons of coolant capacity I finally got my act together and bought an RO/DI unit from the local Reef Supply. I happened to have a ten gallon tub with pump that had been sitting new for years without a purpose under my sink and ultrasonics station. It finally found its calling as my ten-gallons-of-ready-to-go coolant water reservoir.

    For the water unit I also bought an Aquatec CDP 8800 Boost Pump to jack up the pressure, which greatly increases the throughput of the filter unit. I think it runs at 80psi with the adjustment on the pump wide open. I also went for all the auto shutoff stuff to keep from having any morning surprises like pools of water flowing around the shop from forgetting to turn it off. I still manually shut it off when done. Even though it works just fine, my trust of the auto shut off only goes so far.

    Not including the tank and pump which I know I got surplus for a song, I think the rest is in the 225-300+ range for the whole lot. Sure... I guess 300 bucks = maybe 350 gallons of store bought, but time and effort saved made it feel like I payed it off almost instantly.

    Some pics.

    rodi_1.jpgrodi_2.jpg

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    one thing to note - soft water =/= softened water, and what matters in this context is the amount of dissolved minerals, water may be described as "soft" while still having high mineral content which is NOT what you want with the coolant

    that being said - when the manufacturer prescribes tap water for mixing up new coolant, they do this because they want "buffered" water that will not want to absorb CO from the air - something that a purified RO/DI water will most definitely do and thus become acidic, I'm not sure if that will happen when it is mixed up with oil, most likely not, but still

    the idea of RO/DI water for coolant is that you lose water out of it due to evaporation, if you keep adding tap water, that may be soft, but still have high mineral content, each time you dump a bucket of water in there - you add that mineral content to the mix, and it doesn't evaporate, it stays there, next time you add tap water - same thing, you just keep adding more and more mineral content that may upset the chemistry of the mix

    this is why they recommend to top up with purified water, RO removes most mineral content, DI resin will remove ions and UV kills anything that is alive in there

    in my anodizing shop, the hot sealer bath loses up to 20l of water through drag out and evaporation, the total life of the bath is 6 months give or take, so each week there will be 100l of new water added to it, and the added salts there are just 5% of water content, if I kept adding tap water there, even a good one, not overly high on minerals, I'd need a shovel after 6 months when cleaning the tank, not to mention that it wouldn't last close as long if I'd be topping it with tap water

    basically the same thing with water soluble coolant, one customer of mine, I told him his parts are corroded because of an old coolant (brown spots on freshly turned aluminum wrapped in plastic), took a Ph meter with me when I visited him, checked the coolant - 10.8, told him I won't take responsibility for any possible defects until he fixes that, next day he calls me and says there was 5cm (2") of unrecognizable sludge at the bottom of the tank, not chips or fines, whiteish stuff - that is what you get when you top up your lathe coolant with up to 10l of tap water daily for a year or two...

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    Quote Originally Posted by bryan_machine View Post
    ...Any members in the Seattle area actually tried it?
    I've worked shops in Seattle, Tacoma, and the South Sound, and now in Portland. Never used anything but municipal water in my machines, 40 years...

    Thing about Seattle is there is a lot of chlorine in the water. When we put in our heat treat plant, we put in a Lindberg pit furnace for aluminum. Right next to it a water quench tank. When the quench water was heated, it was like standing in a municipal swimming pool, the chlorine smell is that strong.

    But it never caused me problems in my coolant.

    When I disposed of my used coolant, I always had to pay for an extra test to show it wasn't chlorinated paraffins they were seeing, it was just the city water.

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