Cart 0

BOSS GR-100 Glycerin Refractometer Antifreeze Freeze Pt ºF, ºC, %


  • $ 15999
  • Save $ 370

Item Description: BOSS Refractometer GR-100 Portable 0-100% w/w Glycerin Refractometer - Measures Concentration and the Freeze Points in ºF and ºC


New Fire Sprinkler laws got you worried - NFPA 13?  Worry no more! 

You've found the unit to test the concentrations of Glycerin in Water and determine your pipe fluid FREEZE POINT!

This is the Refractometer the Professionals use!

The User's Guide that comes with the unit will show you the Freeze Point of Glycerin and Water Solutions in 'F and 'C!  Consult your product's MSDS/Technical Data Sheet for product specific protocols for measuring their brand of Glycerin based Antifreeze.

 Don't dump your current system!  Check it yourself and know your concentration and freeze points!

GR-100 Specs:

* Scale Range: 0%-100.0% Percent Glycerin in Water
* Resolution: 0.5%
* Accuracy: +/- 1.00%
* Dimensions: 28mm x 28mm x 155mm
* Weight: 138 grams/5.5 ounces

Included are: A plastic hard case, calibration screwdriver, pipette and Users Guide. 


The BOSS Refractometers GR-100 (0% to 100.0% v/v Percent Glycerin Scale) is a hand held Refractometer in a Gray, foam-lined plastic hard case. This unit is SPECIFICALLY DESIGNED for testing of water pipes of potable water.  Calibrate with Distilled Water (water = 0%) and wipe clean with a cotton towel, and you're ready to go!  You have highly accurate results in seconds!  This is a very powerful and simple to use unit that has a GREAT PRICE!  

Pre-mixed solutions are generally purchased at a 48% concentration, so this unit will read correspondingly - 48%!
To find the Freeze Point of your mixture in ºF or ºC, just take your sample reading and apply it towards the users guide.  The user's guide has a conversion from % to the actual Freeze Point of your sample fluid in either ºF or ºC.

For Glycol Antifreeze, please consider our other units designed specifically for Glycol (Ethylene and Propylene) Glycols.


Concentration and Testing

  • Fire suppression systems use a closed loop to isolate freeze-proofed areas. A check valve keeps antifreeze from returning to the main sprinkler system. Glycerin offers highest antifreeze protection at a 70 percent concentration by weight. At this level, pipes are protected against freezing to minus 36 degrees Fahrenheit. Above this concentration glycerine will begin to freeze at higher temperatures: pure glycerin begins to solidify near 32 degrees F. Check with your local Fire Marshal to find the concentration required for your climate. Manufactures offer premixed glycerin solutions though you can blend your own mixture using food-grade glycerin and distilled water. Open the filling inlet to load the antifreeze into the sprinkler system. Use the GR-100 refractometer to test that the glycerin solution is identically concentrated at the filling inlet and at the drain valve at the furthest point in the sprinkler line. Retest the concentration level during the annual inspection of your sprinkler system.

    Go to the NFPA's website for the latest on the current standards:

But don't take our word for it...


"I've had an opportunity to check the use and accuracy of the GR-100 refractometer I ordered and found it to be easy to use and read, and it works exactly as it is designed to. The price is so much better than the electrical/digital models I saw everywhere else that I feel you're offering this device at an excellent price, especially since it gives just as accurate a reading as the digital models.

So, thanks for a good product at an excellent price."

Jim B.  11/23/17


International Clients:

Please be mindful that there can be Customs delays and fees associated with your order.  The delays can be an hour or many weeks, and the import duties can be substantial.  When in doubt consult your local Customs agency to see what the import duties are and if there is a likelihood of a shipping delay.  We are not responsible for delays or Customs/Import Duties.


National Industrial Supply 
30777 Rancho California #891420
Temecula, CA 92589, USA
Sales: 951.308.9269
Fax: 310.733.5480  -  Website:  -  E-mail: