HM Digital

FM-2: Filter Monitor with Volumizer

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Discontinued by Bulk Reef Supply
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The FM-2 RO Filter Monitor with Volumizer tracks up to five filter stages at once by time and volume. The monitor allows you to create filter change points at each stage at an individual point in the future or at a specific water volume. When the preset points are reached the FM-2 will alert you that it's time to change a particular stage. This is a great unit for maintaining your RO Unit.



  • Five independent timers
  • Monitors up to 5 stages
  • Timer counts down in month or days
  • Volumizer counts up in gallons or liters
  • Digital display
  • Easy installation



  • A five-stage filter monitor with five independent timers.
  • The volumizer counts up in gallons or liters (settings can be modified).
  • Works on time (and volume for the FM-2) for up to five stages (can be less).
  • Auto-Off function conserves battery power. The unit shuts off automatically after 5 minutes of non-use.
  • The timer counts down in months or days (settings can be modified).
  • Modern design is perfect for any kitchen.
  • Installs quickly and easily.



Timer Range - 0-999 days/months

Timer Mode -: Days or months (default is months) 

Settings - One alert per stage, up to five stages 

Default Setting - 12 months 

Batteries - 2 x AA (included)

Battery Life - approx. 18 months 

Base Unit Dimensions - 100 x 63 23 mm (4 x 2.5 x 0.9 in) 

Base Unit Weight - 119 g (4.2 oz.) (including batteries)

Flow Switch Cable Length - 93 cm (36.6 in) 

Flow Switch Fitting Size - 1/4" Quick Connect 

More Information
UPC 891144000151
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Product Questions

What is the minimum flow rate for this sensor?
Question by: Jacob on Jun 5, 2023, 2:19 PM
Hey there,
Thank you for reaching out to us. 0.3 l/min

Please let me know if you need anything further and take care!
Answer by: Matt Lucero (BRS Staff) on Jun 8, 2023, 10:05 PM
Any chance you might have the users manual with a font size large enough to read? I couldn't find anything about this monitor on the hmdigital website.
Question by: John Cologgi on Mar 21, 2022, 4:58 PM
Hey John, thanks for the question! I would recommend getting in touch with HM Directly regarding this. HM Digital – 800-383-2777 info@hmdigital.com
Answer by: James Johnson (BRS Staff) on Mar 24, 2022, 2:38 PM
can you install another monitor in the module. so you could measure the amount of water going to system and also out? That way you could monitor your rejection rate.
Question by: Samuel Nunnelly on Mar 8, 2020, 6:53 PM
Hey there,

Yes that would work. You could attach a volumizer anywhere on the system and get a reading.

Take care
Answer by: Thomas Billington on Mar 11, 2020, 12:11 PM
Hi, in case of battery replacement or outage will the devise memorise my own setup?
Question by: Ghassan on Jan 17, 2017, 12:19 PM
Great question! The unit will not save your settings after the battery is removed. You will need to reset the unit to your settings once the battery is replaced. :-)
Answer by: Randy on Jan 17, 2017, 5:41 PM
Can you provide the original setup instructions for starting as new? The HM Digital site only has a sheet for restarting with original settings not disturbed.
Question by: LANNY on May 13, 2016, 9:58 AM
To factory reset your FM2 you will do the following:

1) The factory default settings are 12 months/days and 100 gallons/liters for each stage.

2) To reset to the default settings (if you have changed it), with the unit on, quickly press the SET button. The unit will beep and the "SET" icon will be displayed.

3) Press and hold the SET, UP and DOWN buttons together for 2 seconds. The unit will beep three times. This will reset all five stages to 12 m/d and 100 g/l (deleting any saved settings.)
Answer by: Carter on May 18, 2016, 6:29 PM
Do you recommend putting the flow sensor on the product water line or the water inlet before the filters.
Question by: Matt on Apr 18, 2014, 6:54 AM
Hi Matt,
It will only function on the water inlet line. Fortunately this is the value you want to know anyway, as all of the water (product and waste) both travel through your prefilters.
Answer by: Bulk Reef Supply on Apr 18, 2014, 6:54 AM
Would this work with the water saver upgrade kit? Will the volumizer get confused?
Question by: Kevin on Dec 23, 2013, 6:12 AM
Hi Kevin,
The volumizer only records the water going into the RO/DI unit and it will continue to do so. Since your filters are rated for the amount of total water they are processing and that will remain the same, the volumizer is still good to go (you'll just find that of that total water processed more of it is product water vs waste now so you don't have to run the unit as long to get the same amount of product water). Hope that makes sense!
Answer by: Bulk Reef Supply on Dec 23, 2013, 6:12 AM