Water – Water “Rocks”

I thought that title might get your attention!  Actually, this blog is about “stuff” including, literally, “rocks” that can be found in many water supplies both municipal and otherwise.  It is important to differentiate between things that are dissolved in water that leave “rocks” behind when the water evaporates and things that are in the water that are “rocks” from the start.  Let’s look to the kitchen or bathroom sink for examples.

Many people, including myself, have a little thingies on the outlet of the tap in the kitchen and bathroom that make “bubbly” water.  These thingies, which are more correctly and scientifically called aerators, perform several duties.  Firstly, they nearly always have a restriction orifice in them which limits the flow of water at a specific pressure.  This is known as a “low flow” device.  They also aerate the water.  Aerated water often tastes better than water that has spent its life sitting in pipes.  The addition of air to the water also makes it look like more water is flowing than really is – totally a “cosmetic” thing.  Reduced force and lower flow also reduce splashing.  In any event, these aerators are plagued by both types of contaminants described in my first paragraph.

If you have aerators on your faucets and have a water supply that contains considerable quantities of dissolved minerals (hard water), you will know that the repeated evaporation of water from the end of the aerator leaves a very hard deposit behind.  This deposit, which may also form on the little screen recessed in the outlet, is often called a “lime deposit” and consists of minerals that were probably dissolved in the water from the time it left the source (aquifer, reservoir, lake, river or whatever).  These deposits are, indeed, “rocks.”  They are the same as the stuff that forms on the bottom of sides of a teakettle in repeated use.  Once these deposits form, removing them is next to impossible.  Boiling in vinegar (a respectable acid) may or may not be effective at removing them.  There are also household products that are sometimes, but not always, effective.

If you’ve ever taken one of the aerators apart (probably because it was flowing even less water than it should), you know that there are also small “rocks” that came with the water and got stuck in the little grooves that are part of the aeration mechanism.  I usually dig them out with a needle.  If you look at these little pieces of debris, you see that they are, literally, little tiny rocks with every attribute of a rock you might pick up on a beach on Lake Michigan except for size.  Some of them are made up of previously dissolved minerals that have come out of suspension as “scale” in the delivery pipes but others came straight from the source.  These little rocks are the reason we filter incoming water used in cleaning systems and for other uses.  Although they are usually quite tiny, in some cases they may be of sufficient size to cause damage to automated valves, pumps, flow meters and other devices that have closely toleranced moving parts that are critical to their proper operation.  These “rocks” may also contribute to the clogging of spray nozzles.

Note – Filters, their purpose and their attributes were discussed in some detail in an earlier blog series on filtration.  Type “filter” in the search window for additional information.

Finally, “rocks” in the water have very little to do with its hardness.  Hard or soft water can have or not have the kind of “rocks” we’ve discussed in this blog.  Soft vs. Hard water is a totally different thing which will be discussed in more detail in an upcoming blog.

–  FJF  –

2 comments on “Water – Water “Rocks”

  • Hi John –

    The methods you mention in your email are all good ways to measure water quality. Which one you choose depends on how critical clean water is in your application and, to some degree, your budget. Resistivity is by far the most commonly used measure. TDS can be derived from a resistivity measurement but its accuracy depends on what the dissolved solids are. I am not sure about the temperature sensitivity but will check that out and get back to you. Instruments and means of measuring resistivity are changing all the time and I haven’t brought myself up to date in a while. A true measurement of TDS by evaporation is a time-consuming laboratory procedure and isn’t really appropriate for process control in most cases. I’ll be covering these and other options in upcoming blogs. Meanwhile, if you still have questions, please feel free to get back to me by email at jfuchs@ctgclean.com.

    John Fuchs

  • Hi John,

    Can you please comment or discuss how you would monitor the cleanliness of your rinse water?
    Is resistivity/conductivity a good approach? If so – to what standards? How does heated water affect this reading?
    Is measuring TDS an option? Standards? It this also affected by heat?

    Thank You,

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