Expansion and contraction are important considerations for all fire sprinkler systems, especially for those using antifreeze, which contracts 17 times more than water when exposed to the same cold temperatures. The introduction of listed antifreeze changes how these natural phenomena must be addressed to keep antifreeze systems compliant.
A listed antifreeze product like freezemaster™ antifreeze can have a years-long service life if properly installed, but only if the system itself has also been correctly installed or retrofitted to account for expansion and contraction. Lubrizol, maker of freezemaster™ antifreeze, strongly recommends that an expansion tank be installed along with UL-listed freezemaster™ antifreeze. Here’s why and how to properly install an expansion tank.
Check valves are a common solution to expansion in legacy antifreeze systems, but they risk dilution of the listed antifreeze product and contamination of the water supply. Though both NFPA and UL are highly reputable agencies with the public’s best interests at heart, NFPA standards are less stringent than those of UL. NFPA 13 standard section 8.6 allows for the use of a 1/32-inch check valve to account for expansion/contraction, even for listed antifreeze products. The more stringent UL standard seeks to avoid possible dilution and contamination by requiring an expansion tank and is why Lubrizol strongly recommends one.
While an expansion tank may seem a costly expense up front, it has an excellent return on investment by preserving your listed antifreeze product for longer and protecting upstream water from contamination, both which avoid unplanned costs.
Size: Begin by sizing the tank according to your system volume. Tanks start at one gallon, which may serve systems up to 50 gallons. Though some tanks have earned a UL listing and others haven’t, UL doesn’t have its own sizing guidelines, so defer to manufacturer sizing guidelines during the selection process. Note that very large systems may require a reclamation tank in addition to an expansion tank.
Install: It is a best practice to install the tank in an accessible location like the mechanical room. In totally new systems, your installer can include the expansion tank up-front in the design and install process. For retrofits, your ITM provider can install the expansion tank during initial installation of listed antifreeze or during annual inspection.
Pressure-Match: An essential, often overlooked step is pressure-matching the tank to the system. Tanks come factory-charged with 25 to 40psi, as it would be dangerous to ship with any greater pressure. Most systems, however, are under greater pressure than 25-40psi, and a Schrader valve or air pump should be used to increase the pressure. Failing to pressure-match the tank and system could collapse the tank bladder, negating the benefits of the tank.
Testing the tank is a passive result of annual testing of listed antifreeze: Either the listed antifreeze tests perfectly, which means the tank has been properly installed OR the antifreeze is diluted, which likely indicates a collapsed bladder. Fixing a collapsed bladder requires either draining the system to depressurize it or taking off the tank, reinflating the bladder and reinstalling the tank, both of which incur substantial, avoidable cost.
While an expansion tank isn’t strictly necessary for use with listed antifreeze, it is the best way to maintain the long service life of listed products like freezemaster™ antifreeze and reduce unnecessary expenses. To learn more about installing UL-listed freezemaster™ antifreeze, download the Installation Guide.