Cart 0

$139.99 GR-100 0-100% Glycerin in Water Refractometer 4 Pipe Antifreeze Glycerine


  • $ 13999
  • Save $ 390

Item Description: NI Supply GR-100 Portable 0-100% w/w Glycerin Refractometer



New Firespinkler 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. 



One BRAND NEW NI Supply GR-100 (0% to 100.0% v/v Percent Glycerin Scale) Hand held Digital Refractometer in a Gray, foam-lined plastic hard case. This unit is especially handy 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%!

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




Glycerin as an Antifreeze

  • Glycerin, also known as glycerine or glycerol, is a naturally occurring sugar alcohol. Glycerine lowers the freezing point of water by inhibiting ice crystal growth. Its low toxicity makes it a common choice for weatherproofing residential and commercial fire sprinkler systems. The National Fire Protection Association (NFPA) sets standards for sprinkler systems and requires that any system expected to be exposed to freezing temperatures must be protected by an antifreeze solution. NFPA code 13 requires any sprinkler system connected to a public water source must use a glycerin antifreeze solution rather than ethylene glycol to reduce the risk of poisonous chemicals returning to the water supply. In fire suppression systems containing chlorinated polyvinyl chloride (CPVC) pipes glycerine must be used as an antifreeze as ethylene glycol can corrode the plastic pipes and fittings.

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:


When you compare the GR-100 to digital Glycerin reading Refractometers, it is a bargain in price and accuracy! 

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.

I'd had the glycerine/water mixture drained and then refilled with new by a regular fire sprinkler suppression service. I asked for and watched as they gave me a direct sample of the fluid they pumped back into the pipes. I also asked for and saw the reading from their digital device. I kept a small bottle of this sample, and after the technician had gone, I used your device to check the glycerine/water balance. As I said, what I viewed through your refractometer was a perfect match for the reading on the technician's device, so I'm confident that the unit you sent me is accurate.

In addition to the attractive price, I like the fact that this is NOT a digital device. Since all the parts are "static," so to speak, and the installed prism will not change over time, I feel confident that I can put this unit away, bring it out to use in a year or so, and it still will give readings with the same accuracy as it did yesterday. Perfect for the home consumer to check his own system without having to pay a service to come out and do it.

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

Jim B.  11/23/17


International Clients:

International shipping is via either US Postal's Global Priority (Air) Mail, which is $15.00 and takes 3-8 business days.

Rest of the World: $20.00   Canada: $15.00


Larger orders?

Multiple Orders?

Prefer a different shipping method?

Please feel free to call, fax or e-mail!





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