I moved into a house in northern Virginia and came across this device on the shower head in the master bath. It's about 4 inches across, maybe 3 inches deep. It has a dial that can turn and displays the name of a month in a little window.

There aren't similar devices in the other bathrooms. It does not seem to be part of the shower head itself because of the different finishes.

shower head

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2 Answers 2


The only thing that comes to my mind is a filter, probably activated charcoal, to remove residual chlorine. I doubt that it is necessary with the normal public water system. One sets the month when a new filter is installed as a reminder to change on some schedule.

Such a filter must be changed on some schedule because over time a biofilm will build up on the filter cartridge.


The original poster located this unit https://www.homedepot.com/p/Sprite-Showers-Universal-Shower-Filter-in-Chrome-SL2-CM-R/202386562

  • 1
    the link does not work for me Jan 3, 2018 at 7:17

It's likely a copper media filter for chlorine only, not a particulate filter. I believe copper alters chlorine to something less smelly and drying. Occasionally shake it to keep it working.

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