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FM-2: Filter Monitor with Volumizer - HM Digital

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FM-2: Filter Monitor with Volumizer - HM Digital

81% Recommend this to a friend (13 of 16)

SKU: 200218
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Quick Overview

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 pre set 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

  • LED light indicator and audible alarm (beep)

  • Easy installation

  • See below for full details


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Previously Asked Questions

  • by Kevin on December 23, 2013, @6:12 AM

    Would this work with the water saver upgrade kit? Will the volumizer get confused?

    Bulk Reef Supply 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!

    Do you find this question helpful?  Yes   No

  • by Matt on April 18, 2014, @6:54 AM

    Do you recommend putting the flow sensor on the product water line or the water inlet before the filters.

    Bulk Reef Supply 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.

    Do you find this question helpful?  Yes   No

Full Details

  • A five-stage filter monitor with five independent timers and a tri-color LED faucet indicator disc.
  • 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).
  • The LED indicator disc will illuminate a green, yellow or red light when the water is turned on.  The color indicates the percentage of elapsed time.
  • 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).
  • Includes an audible alarm (beep).
  • Modern design is perfect for any kitchen.
  • Installs quickly and easily.



Timer Range: 0-999 days/months
Timer Modes: 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 
LED Faucet Indicator Disc Cable Length: 92 cm (36.25 in)
LED Faucet Indicator Disc Dimensions: 4.75 (1 1/4" in.) dia., 8 cm (5/16") high 


Patents Pending



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  • Save money By Jose on 1/19/2015

    Great add on works perfectly
  • Just a counter By Paul on 10/22/2014

    I wish these were cheaper as I only use them to count gallons. I put 2 of them on, one before my filters and one after my RO membrane. It's perfect as it tells me how much water I've made, how much water I've used, so I know my ratio, and when I need to change out my filters and gives me an idea of how much water I've sent through my resin so I have an idea of when to change it. Works for me.
  • an item to keep you on point By turbotone on MR on 1/15/2014

    this item is great for a forgetful person.. if this is you get this item!! lol its me for sure but how it benefits you is by monitoring the gallons you use on some of the filters rather then time.. i own a 5 stage system (pre filter, chloraplus carbon filter, matrix carbon filter, 75 gpd membrane and 75 gpd membrane with 2 di stages that i don't monitor because i can visible see and i also have dual tds meter monitoring both of them) pre filters i would change every three months and carbons every 6 months as a rule of thumb.. with this system you change pre filters every 3000,carbon every 6 months membranes are on a time schedule of every 36 months.. i haven't changed my pre filter yet and its been 6 months..just got to the 1200 gallon mark. it makes sense bc I'm running a 75 gallon mixed reef with a 30 sump. i do a 10 gallon water change per week and fill up my 10 gallon ato tank at the same time using about 9 gallons per week total use about 20 gallons a week… i use to do 20 gallon water changes a week at first… keep in mind i have it monitoring after the booster pump but before the very first filter… definitely an investment long term due to the savings in just filter use.
  • Looks good By BobbyT on 12/8/2013

    I think this is a very important device to install on any RO unit.
    Everything is working great so far
  • I would highly recommend for someone that has muliple statages of filter to change a different times. By Kenneth on 11/9/2013

    i highly recommend this tool. It helps to keep track of how much water you are going through, so no more guessing on when to change the filter or how much life you got out of the filter. You can setup a separate checker for each of your stages. I have color changing DI so i know when it needs to be changed, but I still like to know how many gallon of DI water was produced so that I can keep track of my expenses and how the system is functioning.
  • DOA By Russel on 10/29/2013

    The unit has two modes - timer and volumizer. Obviously the more desirable function for the price is the volumizer. Unfortunately the unit I received never detects any flow rate. I was able to get it to detect the flow meter by reinserting the battery - but no matter where I put the unit on my RODI system, it never detects any flow. I even tried blowing air into the flow meter just to ensure the impeller worked - heard it spin, but no reading. Contacted manufacturer to see what the next steps are.... probably going to have to pay return shipping.
  • Awesome Customer Service By Cody on 6/29/2013

    I just installed this today and so far it works as advertised. I spent a while on this site figuring out what the recommended filter change out intervals were and had it all written down ready to program into the volumizer. When I turned it on I found out that it had been pre-programmed to exactly match the chloramines RO system that I had previously ordered. Excellent customer service, above and beyond what I would have reasonably expected.
  • Great little helper. By Troy on 2/27/2013

    I bought a deluxe RO system that had this monitor. It difinitely takes the guess work of when to change filters. fairly easy to use, but the mounting system needs improvement. It uses velcro to mount it and the Velcro goes across the back of the unit which is where the battery cover is, so when you pull the unit off, it tends to pull the battery cover off too. A bracket like on the deluxe dual TDS unit ( or any type of bracket) has would be so much better. Still, a nice addition to any RO system.
  • I have 2 !! By Al on 1/28/2013

    One of these came with my 6 stage value system, but I wanted to know what my rejection rate was, so I bought a 2nd one to count the gallons going into my system. Now I just write down the 2 numbers (water in & product water out) and I can calculate my rejection rates - as well as understand my impact to the water bill. Both units didn't start counting gallons until I pulled the batteries and reset it. Not sure what was causing that, but no issues after that.
  • Helps forgetful people - like me! By Eric W on 9/15/2012

    The total gallon count and countdown options are perfect for keeping track of when the filters need to be changed out. I am extremely forgetful, so this will prove to be useful when it comes time to swap filters and membranes out.
  • Great for Monitoring Filter Use By Pet Store George on 7/18/2012

    Sometimes the store goes through more filtered water than others, so it is hard to keep track of when to change filters. With this, there is no guess work.
  • HM Digital FM-2 not that great.... By Helium on 1/21/2012

    Item worked well till the first battery change. Now will not work with the flow meter. Died after first battery change. No instructions on-line, useless manufacturers website. Now about as usefull as a calender. Lame at best

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