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Thread: Preventing scale build in hot water

  1. #1 Preventing scale build in hot water 
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    I was not sure where to ask this (my first post) but Chemistry seemed the best resort.

    It is commonplace for purveyors of espresso makers, steam machines or even kettles to suggest you use distilled or filtered water to reduce the rate at which scale builds up.

    My intuitive response is in two parts, and I would like some informed commentary on them please:
    1. Most common filters do not remove minerals anyway. Distillation and reverse osmosis filters should do it but they are "overkill" to run the machine compared with simply de-scaling every few months.

    2. Isn't scale-forming measured by the Langelier Index, rather than simply by minerals or Total Dissolved Solids (TDS)? In that case, for water not consumed (e.g. in a steam machine) would it not be more effective to adjust its Langelier Index (e.g. chuck in a bit of Hydrochloric Acid, quoth he lightly) rather than trying to filter the minerals? That is, adjust the pH, Alkalinity and Calcium given an assumed 100C temperature?

    And for the outrageous question, if you adjust water hardness using acid, is this normal, in the sense: is it drinkable?


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  3. #2  
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    Yes, you certainly should use distilled or "filtered" water in these appliances. Filtration in this case means passing water through an ion-exchange resin, not a mechanical filter. The product is also called deionized water.

    Distilled or deionized water is available at local supermarkets in 1-gallon jugs. It is quite inexpensive. Use it in steam irons, for example, because they don't use much water. The iron may go 10 years without forming significant scale.

    The average coffee drinker does not understand any Langelier nonsense, and he does not keep hydrochloric acid in the home. It is absurd to suggest that the typical citizen make any attempt to treat the water himself. He can either buy treated water or descale the appliance regularly with a commercial product (typically oxalic acid crystals).

    Finally, you cannot soften hard water by adding acid. The calcium and magnesium remain in solution.

    *


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  4. #3  
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    Thanks for the first part, Steve.

    On the second part, the average citizen does not drink coffee made out of their swimming pool or their steam cleaner, and the latter swallows water at 4 L/hour (about a gallon) which rate might give even the most devoted espresso-lover pause. The cheapest method of limiting scale build-up for steamers is still relevant, and my interest was piqued because I know exactly how this is achieved in a pool.

    Are you sure about the question of scale formation? Water quality for drinking may go down the tubes but balance can be achieved, as I understand it, with both high and low concentrations of minerals. Neutral or soft water should not cause scale build-up however this is achieved. This is what I still wish to explore.

    cheers
    David
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  5. #4  
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    This is a rigged question, in a sense, since you neatly segue from a homeowner's small appliance to large swimming pools and industrial steam cleaners. We can even continue to the problems of using superheated steam sent through electrical generating plants.

    Each of these situations operates on a different scale, and the operator has an even greater range of training and access to specialty equipment. The effective solution for any one situation is meaningless for the next.
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  6. #5  
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    I am not trying to change the ground rules here, just get an answer to the particular question.

    Anybody?
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